Large Format Photomicrography part: VIII

At this point I haven’t tried to make a print. So far I’ve only gone as far as developing a couple sheets of film to end up with a 4×5 negative. In order to get a look at a negative it will need to be backlit. In the old days this meant using a light box which was really just a deep picture frame containing a light bulb (usually a tube florescent) and fronted by a piece of heavily frosted or opal glass. Light boxes are still around, old and new, with the advent of LED lighting and translucent white plastic they can be had for just a few dollars. That would be a good option if there was a need, but any tablet or LCD display that can be set up to display a solid white background will work nicely.

4x5 B&W negative of assorted diatoms

4×5 B&W negative of assorted diatoms

The Negative Visually

There it is, those are some diatoms. If one looks at the Triceratium (the big triangular one in the center) it’s obvious that a higher power objective was employed. The center of the particular diatoms test is out of focus but the majority it, by this one can tell that the objective used provides only a relatively narrow depth of view. If this was a micrograph (that is a hand drawn image of a microscopic object) then the artist could easily compensate for the narrow depth of field by making slight adjustments to the fine focus while drafting the drawing. In the modern era the fame may be accomplished with a digital photomicrograph by taking multiple identical photomicrographs in which the optical section has been slightly displaced (again with slight adjustment of the fine focus). The image is then combined digitally taking only the sharply focused portion from each to form the final product.

In looking at the negative, even with the bright backlight, it is noticeably dense. There is comparatively little difference between the lights and darks; there’s little contrast. Ideally there should be a large tonal range and significant dark, nearly opaque, areas between the diatoms. Remember, this is a negative so the bright white background of the positive print would need to have a corresponding dense black background in the negative.

4x5 B&W negative scanned as a if it were a color positive

The Scanned Negative

In order to scan a negative one must have a backlit scanner. This could be as simple taking a flatbed scanner and placing the negative on the bed, emulsion side down, with a light box on top while scanning. Fortunately, I have a backlit scanner so I don’t need to bother with such things. In the above image the B&W negative was scanned as if it were a full color positive. Scanning in this way prevents the image from being automatically value inverted by the scanner. During the scanning process the negative is placed in a negative carrier that holds it in position beneath the backlight and neatly crops the unexposed areas at the edge where the film was covered by the holder during exposure.

If anything the scanned negative looks worse than it did against the backlight. There seems to be even less contrast than before.

4x5 negative, inverted and white balanced by Photoshop

The White-Blanced Positive

Now that we’re in the world of digital photo manipulation there’s no limit to what we might do with the image. In an effort to keep things simple the above scan was simply value inverted and then Photoshop was allowed to automatically balance the white. This relatively minor manipulation didn’t increase the contrast of the image, or significantly extend the tonal range. For a first go at a 4×5 negative it’s alright but as photomicrography goes it’s a failure. Because it’s been scanned as a full color image rather than a black and white image, one could go to the small trouble of manually setting the white balance by selling the tones which should be made white, black, and a middle gray. In my mind excessive manipulation is to be avoided so I won’t bother with that.

Defects

In the Photoshopped positive we can see just how little tonal range the image has. There is strikingly little contrast and the areas that should be a pristine white are middle-of-the-road gray. Additionally, in looking at the tonal difference between the left and right hand sides of the image it’s clear that the illumination was uneven.

Settings

This negative was taken using the 20x objective of the BalPlan microscope. The illumination system was run at 9v and no special care was taken to first arrange for Köhler. Only a frosted glass filter was placed in the light path. The shutter was operated at 1/125th of a second, the fastest speed available on the B&L Integrated Camera System II. It was developed in D76 1:1 for 10 minutes under continuous agitation.

Proposal

Working from the assumption that the negative is over-exposed steps will be taken to address the issue. The exposure will be lowered by drastically cutting the power of the illuminator, dropping the voltage by half to 4.5v while keeping the shutter speed the same at 1/125th of a second. Because of the significant decrease in color temperature this will cause in place of the plain frosted filter in the light path a frosted day-light glass filter will be used. In an effort to increase the contrast the negative will be processed in an undiluted solution of D76 for 12 minutes with continuous rotary agitation. According to available information a less dilute solution of developer, and longer developing time will produce a negative with more contrast.

Tray Processing

What about tray processing the negative? Arista EDU Ultra 100 B&W film is panchromatic. Panchromatic film is sensitized to all wavelengths of light meaning it would require processing in an open tray in total darkness. I don’t know that I’m up for making my first attempt at tray processing under total dark conditions. Whats that, do it with a light on then? Sure! Why not?

Fogged panchtomatic negative developed in open tray under red 7.5watt bulb

Fogged Negative

The negative above was processed in open trays under a red 7.5 watt bulb. The outlines of a few diatoms are just barely visible. Note that there is no perfectly clear unexposed area at all on the negative, not even at the edges where it was covered during exposure. When the entire negative show some level of exposure it is referred to as fogged. This is a particularly heavy example of fogging and is caused by exposure of the film to wavelength of light to which it is sensitive prior to the end of fixing.

Large Format Photomicrography part: VII

In the previous post I wrote a little about the options for processing chambers and in the post before that a little about the chemistry that does the work. Now to put that to use!

The Plan

Out of something like home team spirit I’ve decided to go with chemistry from Eastman Kodak. Nothing exotic or home-made; all these chemicals are exceedingly well understood, readily available, economical and are rather more forgiving than some of the film processing guides out there represent. In fact, most photographic chemistry is surprisingly forgiving-there’s just a drive for consistent results that pushes folks into a corner and makes many too afraid to try or to color outside the lines. Everything will be happening in a daylight color print drum.

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Everything needed to process

Film

The film I exposed earlier is Arista EDU Ultra 100 ISO 4×5 black and white. In photomicrographic use lower ISO speed is generally a better bet than higher because it will exhibit a smaller grain size and permit the use of the longer exposures that provide good contrast in this the world of photomicrography. As a rule it’s also far less expensive than ISO 20 film. Many of the older texts on photomicrographic process recommend speeds as low as ISO 7, or even 4!

Developer

I’ll use Kodak D76 as my developer and dilute the working solution 1:1 with tap water for a 10 minute processing time. Kodak D76 is a classic and versatile black and white developer that does just fine in a tray, drum, or tank. What’s more, it’s so widely available that a quick search can usually turn up an account from someone using it in exactly the way a novice is considering. There’s data and recommended processing times for just about every film out there. Guides on stand developing (where there’s no agitation during development), continuous agitation, and drum processing abound. There are dilution possibilities for almost every need and temperature recommendations for nearly any conditions.

First about dilution. One can use D76 straight and undiluted or water it down to varying degrees. As a general rule the less diluted the working solution the faster it acts on the films emulsion. However, It would graph as an asymptote and concentrating the solution beyond a certain point will not decrease the developing time simply because the developer won’t have sufficient time to act upon the films emulsion. Conversely, diluting the solution too much will not extend the processing time beyond a certain point. Put another way, if making an acetic acid and sodium bicarbonate (vinegar & baking soda) volcano one will reach a point where using less acid will not make an eruption just as one will reach a point where using more will not make the reaction continue. For the most part one will not notice a difference in film processed in straight D76 for 6 minutes or D76 1:3 for 12 minutes (some people will claim to see a huge difference but will then proceed to upload zero examples or show anyone their proof). Is there a difference? Yes, one of those is going to look slightly different but unless your pushing the limits making a poster sized enlargement from a 35mm negative and using a hand lens to examine it, you won’t notice it and there are other things that will have a much bigger impact than dilution. Pick a dilution that sounds good and go with it, this is about just seeing if I can do this not if I can make a negative without grain detectible under a hand lens!

As for temperature there is an insane amount of importance placed on it, why? Well anyone who took a chemistry class knows that temperature has a big impact on reaction time, and film processing is all about chemical reactions. The rule of thumb is hotter temperatures cause faster more complete reactions than colder temperatures which still happen but happen slower and are less complete. Some folks read that the packet of developer says processing takes 9.5 minutes at 20˚ C when diluted 1:1 and think that’s a rule. It’s not, that’s just a starting point. That’s just saying that if you always develop under those conditions you’ll always get the same results from an identical negative.

There’s all manner of water baths and water bath heaters that keep ones chemicals at just the perfect temperature for processing. Those would be handy if they were portable but for the most part modern room temperatures are depressingly stable. 20˚ C just happens to be magic, it’s the so called “room temperature” of science. So what temperature should one strive to process at? Why your own personal room temperature of course! Don’t bother with folks who put extreme emphasis on temperature, and don’t bother pointing out the fact that a thermometer that isn’t regularly calibrated can be off by as much as 5˚ C. Is getting a consistent temperature ideal? Yes. Is consistency important? Sure. Is it super-ultra-stress-about-it-so-much-you-don’t-even-try important? Hell no! There’s no need to needlessly complicate this, look up the time recommendation for D76 for whatever room temperature happens to be on site and use that.

Stop

Water water water! Distilled? No! You’re not pumping your drinking water out of a limestone cave, it’s not going to leave hard water concretions all over the place after a minute long bath! Set aside a jug or two of water and let it come to room temperature or just get good at adjusting the taps on the sink. A minute of processing in a plain water stop bath is perfect.

Fixer

Kodak Fixer (Kodafix, a.k.a. Kodak Professional Fixer). Purchased as a condensed liquid it’s diluted 1:3 for the working film solution and takes from 5-10 minutes according to the bottle. I’ll go with 5 minutes. Mixed from powder it’s used 1:1 as it mixes to make the working solution rather than the condensed stock. Unlike the developer which I’ll discard after a single use (it can be saved and one can add a bit of D76R-the R is for replenisher to get it back to working strength) the fixer will be saved. A given volume of fixer has a given capacity of material that it can fix. This capacity is generally rated in some specific quantity that one will have to use to calculate for their own needs.

A volume of 3.8L of 1:3 dilution of Kodafix has a film fixing capacity of 120 rolls of 36 exposure 35mm film. A single roll of 36 exposure 35mm film has a surface area of 0.0465 m² so 120 rolls would have a surface area of 5.58m² which works out to 8649.017 in² or 432 sheets of 4×5 film, if I mix up the whole bottle. My little 4×5 print drum takes not quite 50ml of solution. So 432/3800=x/50 meaning I can mix up 50ml and use it for 5 and a half sheets (5.68 sheets of 4×5 film for every 16.7ml of condensed stock solution).

Fixer should be replaced when it takes twice the time to clear undeveloped film that it took when it was fresh. What does that mean exactly? Take a strip of film cut from a fully exposed but undeveloped sheet (or the leader cut from a shot but unprocessed roll of 35mm) and drop it into your fresh working solution of fixer. Time how long that piece of film takes to turn clear, and that’s the clearing time. The fixing time is double the clearing time. After you’ve processed a whole bunch of film test it again for the clearing time. It’ll be longer than it was when you started but probably not double the original clearing time. Double the new clearing time to get your new (slightly longer) fixing time and keep right on going.

Wash

After fixing it’s time to wash it five minutes or so in a plain water rinse is all that’s needed for that. If someone does happen to have particularly hard water, or a very humid environment it can be a good idea to spend $20.00 on a bottle of something like Kodak Photo Flo. A couple of drops in the final water wash will help dry the film without streaks or water-spots. It handle necessary though and is really just a way to sell photography people a surfactant, Worth it though, if your having troubles on that end of things.

Steps

  1. Load a sheet of exposed 4×5 into print drum inside changing bag
  2. From stock solution of D76 make 50ml of working 1:1 dilution in a beaker (25ml D76 & 25ml tap water)
  3. From concentrated Kodafix make 50ml of working 1:3 dilution in a second beaker (17ml Kodafix & 33ml tap water)
  4. Pour working solution of D76 into drum
  5. Turn drum on it’s side to release developer and roll drum back and forth on table for 9.5 minutes
  6. Hold drum upright over sink to drain
  7. Turn on the sink taps and let the drums internal cup fill with water, release the water roll it around briefly before allowing the water to drain, repeat as many times as possible for 1 minute
  8. Drain water from drum
  9. Pour working solution of Kodafix into drum
  10. Turn drum on it’s side to release developer and roll drum back and forth on table for 5 minutes
  11. Hold drum upright over sink to drain
  12. Remove funnel cap (and cup) from drum and throughly rinse film under tap water at sink for 5 minutes (alternatively place film in high volume water bath for 5 minutes)
  13. Hang film to dry

Timed Audio Guide

The above process is nice if you can remember it or read along as you go. For anyone who’s going to be giving it a go in a darkroom with trays (or anyone who just want’s to hear me ad-lib the whole process) I’ve created a timed audio file. You’ll need to start with the working solutions measured out if your using the file with a drum or tank, or already in trays if your going that route. Everyones phone has a voice recorder theses days so you can of course make your own timed audio guide if you’re using a different bunch of chemistry, film, or temperature conditions. That lovely busy-bee sound you hear is me being lazy and using a motor base to do the rolling of the drum.

Play it in your browser above or here’s the link to download as an m4a, and here’s the link to download as an mp3.

Next time: scans of some negatives and notes on my attempts at tray processing. -K

Large Format Photomicrography part: VI

Apart from the chemistry, (and it’s worth knowing that’s the lingo) in order to do the actual processing one will need something to do the processing in. In keeping with the philosophy that the best material is worthless if one hasn’t got it I’ll begin with something that’s likely to be on hand, and move forward from there.

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Film processing tanks

Tray Developing

No need to rush out and order some fancy perfectly size plastic or enamel developing tray, a cheap plastic storage box or even a Chinese take out container can serve as a processing vessel. If going this route one will need three trays to make things easy, and a darkroom. Don’t discount this as an option if a darkroom isn’t available. Working at night can go a long way to solving most of the troubles of setting one up and a roll of aluminum foil and some masking take can handle the rest. There isn’t really a need for a safe-light but it goes a long way to making things easier. There’s no need to buy a fancy or expensive safelight either, a can of red spray paint can transform a standard lightbulb. The ubiquitous smart-phone displaying a full screen solid red picture works just as well, it’s a little safer to just adjust the display settings for a deep red tint though.

One will have to figure out the volume of chemistry to get a centimeter or so of depth in the trays. Additionally, a pair of tongs or rubber gloves will need to be used for shuffling the film about in the tray and moving it from one to the other. Some photographers wouldn’t touch tray processing for anything and others wouldn’t dream of doing anything else. It can be pretty daunting to start with tray processing and the need for a darkroom can turn a great many people off.

Darkroom Film Tank

If trays aren’t to ones liking, a film tank will do. These are basically deep open tanks into which one dips the film after loading it into a specialized hanger sized exactly for a sheet of film. Darkroom tanks require significantly more chemistry than trays but have a smaller footprint and due to the lower surface area they expose the chemistry stays fresh a bit longer than an equal volume in a shallow tray-great news if you’re running a school darkroom on a shoestring. The hangers keep the individual sheets of film from touching and run a dollar or two a piece on the second hand market.

Daylight Film Tank

Particularly dexterous photographers can process as many as 10 sheets of film in trays at once without any issues, other folks struggle with scratches from a single sheet. Just as one can process 36 exposures of 35mm film at once in full daylight provided it’s been loaded in the dark, so can one processes a number of sheets of 4×5 in a daylight cut film tank. There are a number of vintage and modern options when it comes to these sorts of tanks and they run the gamut as far as quality and cost goes.

Downsides to daylight cut film tanks abound. The vintage ones are inexpensive but leak like nothing else and may be rather incomplete. They require a heroic volume of chemistry, many take 2 liters or more. New systems, such as the Combiplan, tend to cost a ridiculous amount for what they are but don’t leak and use far less chemistry. All of these will be a struggle for anyone working in even the largest changing bags. Still the old tanks from Yankee hold 10 sheets and only run $20.00 or so second hand, just don’t make the mistake of shaking them all around like one would do with a 35mm tank.

Daylight Print Drum

Ostensibly made for processing prints, daylight print drums are available in a range of sizes, including 4×5. The small black tube in the photo above from Ilford Cibachrome is only a bit larger than an empty roll of toilet tissue and can handle one sheet of film at a time. Larger drums can handle multiple sheets and different brands have different takes on the internals with channels and grooves to keep multiple sheets from overlapping or knocking around. As new old stock one can expect to pay $10.00 or so (including pack and post). Daylight print drums use very little chemistry, are inexpensive, and can be quite convenient provided one doesn’t need to process a couple dozen films in an hour.

At their most basic processing drums of this sort are a hollow tube with a light-tight drain on on side and a light tight funnel and cup combo on the other. Hold the drum vertical and pour the chemistry in to the funnel where it gets caught in the internal cup. Tilt it onto it’s side and roll it back and forth on a table to start processing, or spring for a motor base that will rotate it at the push of a button. A couple hardware store casters screwed to a scrap of wood will do for a manual roller base if space is tight. Flip it on it’s end to drain the chemistry and move on to the next step.

Daylight Cut Film Drums and Tanks

There’s a whole range of brands out there that can handle cut films. Some of them work more like the 35mm daylight film tanks that look and work pretty much like a cocktail shaker and others look more like a daylight print drum. They are all hopeless overpriced for anyone who doesn’t just want to dip a toe in and test the water. Get ready to shell out $300.00 or so just for a Jobo tank (never mind the film insert) or any of a dozen exotic film holders that will fit in a standard three reel 35mm film tank.

The Jobo’s are a breeze to load up and use while most of the insanity that they call 4×5 “reels” are variations on the trials of Hercules, hard enough in the light and true madness in the dark. They require a motor base in most cases or a bit more thought out placement of casters for manual rolling because of their more complex construction-the chemistry might not be evenly distributed if it’s just rolled on a table.

Daylight Roll Film Tanks

Grab a plastic two reel Paterson super system 4 and search the web for “4×5 taco method”. It’s easy, it works, it’s affordable, and if one picks up two multi-format plastic reels with it one can process their own 35mm and 120 roll film too. This is the way to go for anyone who isn’t adventurous enough for trays and is to wary (or just unlucky) on the second hand market. Anyone lucky enough to have an area photography store can pick up the gear for this new in store while everyone else can support the few stores still out there by buying it new from a website and having it shipped.

Conclusion

There is an option out there for anyone who needs one. The goal here is just to get one print so the daylight print drum is the way to go, no darkroom required and it’s small enough to fit with room to spare even in a small changing bag.

Don’t get discouraged if you were hoping to see me flub an attempt at tray processing! I just hung a few black sheets around my basement utility sink and I’ll be flailing around in there as well!

Large Format Photomicrography part: V

Previously the general program and goals were covered. After which a ground glass focusing screen was cobbled together. A plan for a home built 4×5 photomicrographic camera was outlined, all before finally exposing a sheet of film. This is the point at which enthusiasm begins to come up against the fear of chemistry and nyctophobia that plagues analog photography. Whatever else the writer might be, he is certainly not a chemist, a well-informed photographer, or particularly strict in his adherence to procedure. Fortunately, apart from all that, he is as well not one for whom fear of failure (or failure out-right) has ever been dissuasive!

Now, one could without too much searching locate a mail-order film processor who would happily provide a mailing label and some assurance. Safely packing off ones exposed film (still in holders) to an accomplished film processing service is not for everyone however, and potentially as expensive as processing it ones self. There are a few choices to make, and some purchases that will likely need to be made.

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Assortment of powder and liquid photographic chemicals

Here’s what one is going to need:

  1. Developer
  2. Stop bath
  3. Fixer
  4. Developing chamber

That’s all, four things, simple. Developer and fixer can be daunting but it needn’t be, it’s available as kits from all manner of specialty shops on-line, the only hard choice is what to get. First one will need to decide to go with color or black and white. Obviously this is contingent of the film that was used in the earlier posts but one can always choose to color outside the lines and cross process (develop film in alternate chemistry). Black and white processing is simpler so one can’t go wrong with that as a first choice. There’s all manner of options even after one limits the choices to black and white developers but one can generally put them into two very broad categories based on the manner in which they are sold, those that come as dry powders and those which come as a liquid. There are positives and negatives to either but the chief among them is generally perceived to be lifespan.

Developers that are sold as a liquid may be provided as a single concentrated solution or a couple concentrated solutions. Those of both types are added to a prescribed quantity of water to make what is called a working solution that will be the actual developer used. The developers that are sold as a powder have an indefinite shelf life, until they are mixed and the same may be said for most liquid developers. So-called Pyro (PMK or Pyro-Metal-Kodalk) developers generally have a phenomenal shelf life and as a single use developer (working solution discarded after use) may be a good choice for someone who expects to only process a limited number of films in a given year. Regrettably, even as developers (essentially all of which are toxic) go Pyro developers are on the far end of the safe/environmentally friendly spectrum. Pyro developers also impose limits on the stop bath and fixer that one may use in a later step. A concentrated liquid developer such as Ilford’s Ilfosol-3 may be a better choice for anyone who wants to keep their options open.

Powder developers are well worth consideration. One of their modern-day assets, and one which should not be overlooked, is the ease of acquisition. All powder developers are freely shipped to any mailing address through the normal mailing services, they require no special hazard labeling, address requirements, or delivery services (a number of liquid developers are disallowed by the USPS and may not be shipped to PO boxes or residential addresses). The concern that puts many off of using a powder developer is primarily of shelf stability and mixing. Preparation of the developer from powder is far simpler than one may expect. As most home plumbing can supply water at the recommended mixing temperature an inexpensive pitcher, spoon, and thermometer are all that is required, then follow the directions on the packet. Self stability of the mixed solution may be easily addressed by keeping the mixed developer in full, small, brown plastic bottles-the sort in which hydrogen peroxide is sold are excellent. Most powder developers mix to create a US gallon of concentrate and will fit exactly in four, empty, one quart, hydrogen peroxide bottles.

The stop bath is more restrictive for color film processing and one may employ a plain water stop for most black and white processing. There’s no need to buy a specialty stop bath although of course, it is an option some photographers will never give up.

Fixers are a necessity however, and much like developers are available as both powders and concentrated liquids. Shelf life is generally not an issue with fixers and unlike developers are frequently used for multiple rounds of use before they are discarded. The two primary varieties of fixer are those which are acid and those which are called archival (base). In a general way one can always achieve acceptable results by making use of the flagship fixer made by the same company that produces the developer. Alternatively one is free to make use of the classic standby, sodium thiosulfate, popularly called plain hypo or photographers hypo. Hypo has the particular benefit of being widely and inexpensively available in brick-and-morter pool and hot-tub supply stores where it is sold as a chlorine reducer.

One may as well employ a dedicated final wash but much like the stop bath it is a matter of personal choice. To many it’s an unnecessary complication that is best when in the form of plain tap water.

This is already too long so next time, developing containers! -K

 

Large Format Photomicrography part: IV

The earlier posts of this series have covered everything up to making the exposure, and took a bit of a detour to outline a method for performing the work with an improvised camera. At this point one is expected to have a focusing screen, a loaded 4×5 film holder, and an attachment or integrated camera compatible with the same. Two additional items that will prove helpful but are not strictly necessary are a simple hand-lens (a linen tester or tripod magnifier is ideal), and a photographic light meter. I understand that there are smartphone apps that can serve as a light meter, but I have no recommendations on that front. The remainder of this installment will take the form of a checklist.

  1. Place the focusing screen on the bellows of the integrated or attachment camera.
  2. Properly align the illumination source, the brightest available is ideal but depending on the ideal color temperature for the film non-standard sources may be preferable to those used for normal visual work.
  3. Place a specimen on the stage either in the object holder of a mechanical stage or beneath the stage clips (even if neither are usually employed).
  4. Where available make use of voltage control or dimmer to moderate the lighting to a comfortable level for visual work. Neutral density filters may be employed where the lamp may not be otherwise moderated.
  5. Obtain clear visual focus at the ocular.
  6. Where required (as in the photomicrographic BalPlan head) divert the light path from the ocular into the path of the attachment or integrated camera.
  7. Remove any neutral density filters in use or turn up the dimmer to provide the color temperature dictated by the film.
  8. Where available set the shutter speed to “T” and activate the release to illuminate the cameras light path. If “T” is not present but “B” is employ a locking shutter release.
  9. Where available (as in the Integrated Camera System II) focus the image projected on the ground glass using the control on the camera body. If the image will not focus (as is likely if using an improvised camera) one will need to adjust the length of the draw-tube or camera bellows to achieve focus. Do not focus the image on the screen by operating the focusing mechanism of the microscope-doing so will exaggerate any optical defects present.
  10. Use a hand lens to view the image seen in a clear area of the focusing screen to achieve fine focus without the interference of the grain of the focusing screen.
  11. If available place a light meter over the center of the focusing screen and using the reading calculate the necessary exposure.
  12. Close the shutter mechanism and set the shutter speed founding the preceding step. If using an improvised system without a shutter place a light opaque filter (i.e. tin foil) in the path of the illuminator.
  13. Remove the focusing screen and replace with a loaded film holder.
  14. Remove the dark slide from the holder.
  15. Operate the shutter to make the exposure.
  16. Replace the dark slide.
  17. Note the settings that were used to make the exposure if known. The voltage of the illuminator, color temperature, light meter reading, setting of the cameras control, and shutter speed are of particular usefulness. One should of course note the slides catalogue number, the objective, and ocular (if using one in the cameras light path), used.

The Bausch & Lomb Model R part: IV

The Model R isn’t as common as many other microscopes of the B&L brand. In fact, significantly older and more professional stands often command far lower prices than the Model R does on the second hand market. It’s commonplace to see the Model R (and similar Gem and New Gem) microscope selling for $120.00 US. This is perhaps on the more reasonable side of things when one considers that while in production the Model R commanded a weeks wages for a common factory worker. Currently, a worker making the US federal minimum wage would need a bit less than a week to afford the microscope and someone earning the median hourly rate in 2018 of $22.13 could afford one after a days labor.

Without looking at the numbers for a great many other microscopes it’s hard to claim the Model R has held it’s value more or less than other stands. One would be foolish to claim it’s due to utility more than rarity without some investigation. Suffice it to say that a Model R makes an entirely serviceable field microscope while a modern introductory stand (even the rare model to make use of a mirror rather than an electric lightbulb) would make a poor companion out in the field. With the Model R there’s no need to carry along the box, or even the foot, simply take the body and a pocket of slips (and cover slips) off to the nearest stream or creek. A drop of water is more than enough to keep the cover in place and one need only point the stage towards a nice white cloud, or even the clear blue sky, for ample light.

Most everything written about the Model R tout it as a simple and sturdy introductory microscope for a child. It’s size seems to support this notation as well. However, when one considers the text with which the microscope came bundled it’s not so clear that the claim rings true. One must acknowledge however, that in decades past the educational recreations permitted youth were, let us be direct, far more complex than those which our litigious permits today.

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Modle R with companion book and Student model for scale

Dr. Julian D. Corrington’s monograph Adventures with the Microscope was published in 1934 and written while Dr. Corrington was working at another Rochester, NY area institution, Ward’s Scientific. Primarily an educational scientific supply house Ward’s served educators and schools far and wide, as they continue to do to this day. The above book was for all intents and purposes a handbook and companion for the Model R. Throughout the prolifically illustrated text one finds halftone prints of the Model R, Gem, and New Gem (as well as numerous more advanced and specialized instruments). This was a book written for one who would enjoy the use of the Model R at home, and gravitate towards the more costly stands in their time at school.

Dr. Corrington’s book was written in a friendly style that was far more amenable to a complete reading of the text than most other works on the microscope. At the same time one may jump freely between chapters, which are largely centered on the technique to be employed or the object to be observed, without the feeling of having missed out on an important prior section. At some 429 pages (excluding nearly 30 additional pages of appendixes and index) it is as comprehensive a text as one may hope for. It’s a work one might rarely need to exceed in the pursuit of microscopy.

Sadly, Dr. Julian D. Corrington’s Adventures with the Microscope has been out of print for decades and too many who search out an introductory text are apt to find the slim volume of nearly the same title put out by Richard Headstrom, Adventures with a Microscope. The work is still under copyright and is slated to enter the public domain in 2049 (date of the authors death +70 years). It’s telling, I might point out, that a quick search on Worldcat.org shows four universities with copies of the book, all within 60 miles of my home, some 62 in the continental US hold copies. Whomever the target audience of the work may have been at publication, it’s found a home with college level students today.

Link to the book on AbeBooks.com

Link to the book on Amazon.com

One day soon we’ll look at some of the exercises from the book and compare them to those in similar texts. -K

The Bausch & Lomb Model R part: III

The question of the determination of a microscopes magnification has a distinct tendency to be treated in either a profoundly technical way or only the most basic terms, never mind the source. On the simpler end of things it’s often put similarly to this: the magnifying power of a microscope is determined by multiplying the power of the objective by that of the ocular. Well, lovely. That certainly buttons that up doesn’t it, no? There may even be a few lines here of there on the power of an objective or ocular but all such texts take it as given that the optical components will be marked. At the opposite end of the spectrum one will find page after page of complex optical formulae and jargon like principle poster focus and Ramsden disc. Fortunately those formulae that are printed can be made rather more meaningful to most people by simply substituting words for symbols, as such:

Magnifying Power = Tube Length x Distance of Distinct Vision / Focal Length of Objective x Focal Length of Eyepiece

Which is great, if you want to muck about in physics class and measure the focal length of your lenses. One could of course forego that in favor of a little bit of basic math, if one had an eyepiece micrometer and an object micrometer, but then the Model R uses non-standard diameter optics so the chances one has an reticule of the right size for the narrow ocular is slim, and in any case it’s a closed system-not something one would easily disassemble. So what if you haven’t got anything, not even a stage micrometer? I mean the Model R was made for kids right, what kid just happened to have a hankering for a stage micrometer first thing when they got a microscope? Alright, maybe a lot of us did, so we’ll use one but bear in mind we can do this with any object that has a known diameter, like a human red blood cell (7.2 microns at the widest point) or a human hair (in the neighborhood of 70 microns is diameter.

All the physics used to determine magnification is well and good but pales as a practical exercise for the microscopist to comparing the known size of a particular object to the magnified size of that object. In order to do that with math one needs to know a great many things about the lenses to begin with, most of which is best suited for classwork in physics only. In order to make the same comparison in an almost exclusively practical way one need only set up the Model R (or any microscope) as below.

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  1. Place the object of known size (be it a blood smear or stage micrometer) on the stage and focus the microscope.
  2. Incline the joint so that the microscope is horizontal The Model R hasn’t got an inclination joint but the body and stage comes off from the foot and may be mounted horizontally.
  3. Use a rule to position the exit pupil of the microscope 250mm from a sheet of paper taped to a wall or other support.
  4. Position a bright, high intensity light source so that it may be focused on the specimen from below the substage.
  5. Turn out the room lights.
  6. Mark the locations of several divisions of the micrometer or a few red blood cells on the paper.

Now that the paper has been marked only one further measurement is required. The marks made by projecting the specimen on the paper are of a known division. They are also of a size that may be easily measured with convention means.

  1. Use a rule marked in millimeters to measure the divisions marked on the paper.
  2. Line up carefully and note the number of divisions on the paper that are needed to span the distance perfectly between any given number of either.
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Yes, I did chose to awkwardly lean over the entire setup rather than walk to the other side of the table!

Now for the math, in this case the formula is much simpler than one might expect. One need only divide the distance as measured on the ruler by the known measurement of the magnified and enlarged divisions marked on the paper. Therefore if the divisions of the stage micrometer are 0.01mm, and at the Model R’s most powerful magnification (draw tube fully extended) they measure precisely 4 divisions in 12mm the formulae would be 12/0.04 = 300 diameters of magnification. It’s pretty nice to see that that confirms the marking on the draw tube. Repeating the process with the draw tube fully retracted one finds that 2 divisions as marked on the paper span 3mm exactly, 3/0.02=150 diameters of magnification.

With this knowledge one can accept that the marked powers on the draw tube are accurate, but that doesn’t inform on the individual power of either the objective or ocular. One will of course recognize that removing the front element serves to reduce the power of the entire system by half as that is what the markings indicate. Unfortunately this does not enable one to know the power of the individual elements. One need only repeat the process without the ocular to find the power of the objective alone. It then becomes a simple matter to know the power of the ocular, power of the entire system / power of the objective = power of the ocular.

Repeating the steps above, except to this time measure 250mm from the rear of the objective lens provides the following measurement. Twenty divisions (marked in intervals of 5 each) measures 4mm on the paper. Such that, 4/0.2=20 meaning the power of the objective is 20x and the ocular is therefore 15x which further indicates that removing the front lens element reduces the power of the objective to 10x.

The Bausch & Lomb Model R part: II

It’s time to see how the optics of the original B&L Model R perform. To begin with a few common test objects, beginning in this instance with the wing of a fly, will be evaluated visually. Then, the next visual test will be the scales of a Podura springtail followed by the more finely striated Pleurosigma angulatum. The ability to resolve the features of these objects once served the same descriptive needs that the numerical aperture measure serves now.

It’s worth mentioning that no special effort will be made to ensure perfectly clean elements, so although this microscope is in exceptional condition for a stand of its age one could expect to see a not insignificant improvement in resolution should the effort be made. All photomicrographs taken will be made with a ring-stand supported iPhone camera. To avoid putting up an over abundance of images that will will only be given a cursory place only two images of each test object will be provided. The lowest power is that marked on the Model R microscope as 75 while the highest power is that marked as 300. It’s worth noting that to configure the Model R to provide the lowest power one must remove the front element of the objective lens and set the draw tube to its shortest length. To achieve the highest power one must use both elements of the objective and set the draw tube to its greatest length. Lighting is provided by a high variable intensity condensed B&L illuminator.

In the low power photomicrograph we can see that there is some indication of markings on the various cells of the wing and make out a pattern of hairs on the costa. At the high power end of things we can clearly see the individual hairs of the costa, they are not the toothy spikes represented on the first photomicrograph. The pattern of hairs on the marginal cell is clear but the individual definition is somewhat obscure. It is not immediately clear that they are in fact raised hairs, easy enough to determine with a bit of back and forth of the focusing knob. All things considered the imaging abilities of the microscope are surprising. The axial third of the field of view is surprisingly clear and sharp, even when viewing so comparatively thick a specimen as a fly wing. Except at the lowest power, without the complete objective in place, there is very little evidence of chromatic aberration.

In the low power image of the podura scales we are able to discern some implied texture on the surface of the scale, it’s obvious it is not simply a color gradient. Again it is clear that there is some chromatic aberration, more in evidence due to the slight misalignment of the illumination source, but one should expect that when using a divisible objective. Turning to the high power photomicrograph the texture becomes a clear pattern of lines although, one could certainly not make any secure judgment as to the nature of the texture in cross section. It should perhaps not be surprising that the Model R can make no clear statement on that count, there was in fact profound disagreement on the form a podura scales texture would have that was unsettled until the rise of electron microscopy. As a side note, these scales are not intact lined but rather feature a pattern of lines composed of fine hairs.

Although the Model R did not provide the performance of a professional stand on any of the test objects thus far it certainly stood tallest on the fly wing. It’s then somewhat pointless to set it against the Pleurosigma angulatum as there’s little reason to expect it to resolve the finer points of the diatoms test. Fortunately, one would hardly expect someone to put such a difficult object before the Model R. It is gratifying though to note that if hard pressed one could certainly enjoying viewing diatoms with the stand, clearly it’s not the ideal object one might chose to observe but it certainly performs far better than one might expect. The red and blue fringes of an achromatic objective are obvious on the photomicrographs of the diatoms; they are by no means reason to disregard the Model R. It would be a great thing if a microscope of this quality were put before every elementary school student rather than the sort of needlessly complicated and overly ambitious toy one can find at any of the “science” themed stores that exist in shopping malls and digital marketplaces.

In part III, a few simple tests one can perform to find the powers of the optical elements. -K

Large Format Photomicrography part: IV

Photography Basics / Darkrooms

Not having a darkroom doesn’t mean giving up on large format photography; there is a darkroom solution for every problem out there, ranging from fully equipped professional quality spaces all the way to under a comforter, with the lights out, at night. One could run over to a site like localdarkroom.com to see the spaces available in ones area and, if fate is kind, find out a nearby space can be had for a nominal fee. If everything is hopelessly far away or self reliance is more ones style it’s just a question of expense. Free solutions can be as simple as waiting for nightfall and putting towels over every bit of light in evidence in a darkened bathroom, or cleaning out a little space in a closet.

Buying a photographic changing bag or darkroom tent is certainly an option. A changing bag is essentially a darkroom, for ones hands. A fairly large changing bag may be found in the $25.00-$40.00 USD range on any of the countless “we have everything” web-stores, just search for “changing bag.” If going that route don’t try and save a little cash by purchasing an undersized bag that’s really only useful for 35mm work, unless of course that’s ones ambition. Except in cases where every penny must be pinched it’s generally good advice to buy the largest changing bag one can afford; something about darkness turns a meter into a millimeter.

Photography Basics / Holders for 4×5

With some sort of perfectly dark place, a box of film, and a film holder one’s all set to load some film. The assumption here is that one will be loading up 4×5 film into a 4×5 holder.

If working in an improvised dark room take a moment to lay everything out that will be needed in an orderly way. It’s imperative that the box of film be fully reassembled as the final step; it’s no fun at all to have the lid of a box go missing as a result of a cluttered workspace. Where at all possible bring everything that is needed and only what is needed into the darkroom, whether that darkroom is a closet or a changing bag. It’s a good habit to open up the dark slides of the film holders as shown before going dark; closing the holders then only after film has been loaded. In this way one avoids both failing to load film and wasting time trying to load a sheet in a full holder.

Before the actual business of loading a few notes on film holders and loading 4×5 film. Holders usually have two sorts of indicators to avoid loading film incorrectly and double exposures. The first indicator is less universal and is based on two colors, white and black. One side of the dark slides handle is apt to be painted white or molded from white plastic. By convention this side is placed facing out when the film is un-exposed; it’s ready to see the light. After exposure the dark slide is placed back with the opposite (black) side facing outwards, indicating that the film has been exposed and should only be removed in the blackness of the darkroom.

Vintage or antique film holders are liable to have plain metal dark slide handles (or to have had all their paint worn off). Moreover, one can hardly observe the color on the dark slide when working in a darkroom or changing bag. All film holders thankfully have a second indicator which most commonly takes the form of  one or more raised or recessed dots on the upper right hand corner of the dark slide when viewing the un-exposed indicating side.

In addition to indicating the exposed or un-exposed state of a loaded film holder the raised dots serve as a reminder of how to properly load film. Every sheet of film has two sides, the emulsion side and the back. The emulsion side is the side which has been coated with light sensitive material and is the side which should be exposed to the light from ones camera lens. Unlike 35mm film which can only be loaded in one direction (as a result of the cartridge construction) 4×5 film can easily be loaded backwards. To address this issue every manufacturer includes a small indicator on each sheet of 4×5 film.

The indicator takes the form of one or a series of shaped notches in on corner of the film. Different patterns of notches indicate different types of film, speeds, manufacturers, and emulsions. Explanations of the notches is beyond the scope of this post, see the film makers documentation for details. Just as the raised dots of the dark slide should be in the top right when the film is un-exposed so too should the notches in the film be in the top right when loaded. If the notches are loaded such that they are in the top right, whether one loads the film by sliding it up from the bottom of the holder or down from the top, it is not possible to face the emulsion side away from the lens. Thank goodness for chirality.

Photography Basics / Loading 4×5

One should prepare for loading 4×5 film holders by giving them a good clean up. Take a clean, 2″ paintbrush, just the sort one would use for painting trim or moulding, and brush out the film holders. In a similar vein it’s frequently recommended that one use some sort of air duster for the task. The thought of so powerfully propelling dust into the air at a time when it would rather be settled seems enough to proscribe that practice. Pull all the dark slides out only so far as to expose the channels into which the film will be slid. Don’t pull the dark slides out all the way, doing so only serves to clutter up the work-space. At the same time do not think to simplify the task by only pulling out the dark slides a very minimal amount; one should be able to bend the partially loaded film slightly upwards to tell that each side is uniformly slid into its channel, a task that’s impossible if the dark slide itself is holding down the film.

If a picture is worth a thousand words I own at least one now.

Well there it is, enough to get anyone loading 4×5 in no time at all.

The Bausch & Lomb Model R part: I

The microscope is something of an emblem of science. Unlike similar fetishes of science such as the test tube, the microscope stands as well as a banner for the curiosity of scientific pursuit. It’s an amazing thing and has had an impact on the sciences similar to that the automobile has had on transportation. Fortunately, while the automobile exists in a state of age restricted licensure, the microscope is available to all-or is it? What about price? What about the availability of something serious but attainable? What of something in between a fly swatter and an atom bomb?

Over the years the optical company Bausch & Lomb has broken new ground any number of times in the world of microscopy. Growing up outside Rochester, N.Y. it was something of a given that the microscopes in school would bear that prism-shaped logo and great treasures would be hidden away in the attics and sitting rooms of my childhood. These were all, however, great heavy things of cast iron and brass, replete with fragile glass elements and cases bigger than any bread-box. There was something else though, something different, and it started with the Model R.

Sold in the 1930’s during the years of the world-wide economic downturn popularly called “The Great Depression” the Bausch & Lomb Model R had a retain price of twenty-one dollars in the United States. Depending on the precise year one elects to compare that equates to anywhere from $300.00-$400.00 in todays currency. This was a time when the average factory worker was earning some $0.40 an hour and could expect a weekly paycheck which would only just cover the cost of the Model R. It was accessible but surely out of range of anyone without the willingness to sacrifice to obtain it.

The styling of the Model R was such that considered on it’s own it would not seem out of place beside a professional instrument from its day. Black enamel paint and bright nickel plating were the norm. The look is replicated in the Model R with a glossy black Bakelite stand and shiny metal body tube. A few points that quickly stand out are the lack of an inclination joint, the single focusing knob and total lack of a fine adjustment.

Then there is a draw tube… What? No! To dispense with the need for a nose piece and multiple objectives, a pair of which would cost more than the entire Model R, this microscope made use of a varifocal lens system (rather like but distinct from a zoom lens system). With this simple change the microscope was enormously reduced in price.

While today one might expect a plastic snap-case if any were provided at all it’s well to remember that in the 1930’s when an item came with a box it was as likely to be wood (perhaps more so) as pressboard. So if the look of the Model R were a product of it’s time, what can be said of it’s utility?

For that, watch this space for part II where the Model R will be put through it’s paces -K