How The Posts Get Made

In the somewhat vain hope that anyone wonders about how this blog gets written, I thought I’d write about it. In the present state of things I write the actual content out on paper, yes paper. The paper is an A4 pad on top of my Wacom Bambo Slate. The Slate syncs the writing over Bluetooth to my phone where it is exported as text via the Wacom Inkspace app (or website) then into the Pages word processing app or even directly into WordPress. From there I do a bit of editing, add pictures or what have you and call it a post! The process is a bit convoluted but it allows for me to do my writing while traveling for work, as I am now, or in the lab where I might not want to set up a laptop. I find it particularly appealing that I do end up with a paper copy of whatever notes I may take as well as an automatically synced copy in the cloud. I’m sure its not a process that would work for everyone, but it works for me.

-K

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Large Format Photomicrography part: III

The Homemade Camera

At this point I’ve got everything I need to shoot some 4×5 film. I could load some film into a holder, and start shooting without any delay. I wonder though, what about everyone else? What if I didn’t have a trinocular BalPlan, a working System II shutter assembly, the proper camera body, and the right adapter? What if all I had was was a basic monocular microscope and dreams of shooting 4×5? Could I get away with something simple and homemade or would that be too impractical. Thinking about the preceding one is apt to consider the old standby of shoe-string photography: the pinhole camera. Such a camera need be nothing more complex than an opaque box with a pinhole at one side. It should then be entirely possible to use the same principles in the task at hand; replacing the pin-hole with a microscope wouldn’t do though. One would need some way of determining focus. Depending on what’s to hand it may prove more or less feasible to solve the problem of focus by building two cameras; the one for focusing only a screen of some sort in place of a sheet of film. Two identical carers could be easy (perhaps two identical shoe boxes) or nearly impossible at a moments notice (the recycling picked up yesterday). In any case I have a ground glass and a film holder so a single camera seems easier. A student should be able to borrow both from the art department or one could buy a holder second hand and make their own screen easily enough.The question now becomes how to attach the box that will be our camera to the microscope. With a basic monocular microscope with inclination joint, using it in a fully horizontal arrangement seems ideal. One needn’t bother with standing on a chair to view the screen or precariously balancing the “camera”. So far, no consideration has been paid to the question of a shutter. The simplest option would be to ignore a shutter in the traditional sense and merely block out the light source with a bit of light opaque material, tin foil, for example. Then we need only consider the need to ensure that the only way light may enter the camera is through the microscope. Easy enough, a hole only just the size of the ocular tube is made in the camera and the connection masked with a bit of gaffer tape. All that remains is to consider how the film holder will be held to the box. This being the most complicated aspect of construction it has been left for last. One need cut away enough of one end of the box so that the light may reach the film. This hole may be made large enough to utilize the entire film or it may be masked so as to provide a circular photomicrograph. With the hole cut one should then glue a few layers of soft dense material to the area the film holder will press against. This material will serve as a light seal. A few layers of dark colored fleece or soft foam insulation will do nicely. To hold the film holder in place one has a number of options, the first that occurs to me is to poke four holes through the box and insert through the same a pair of dowels or pencils, mask the ends with tape for a tight fit, and then stretch rubber bands from end to end to hold the film holder tight against the light seal.

1. Place the specimen on the microscope stage and position the “camera” at the ocular.

2. Affix the focusing screen to the camera.

3. Turn out the room lights, turn on the illuminator, and focus the microscope.

4. Taking care not to move anything, remove the screen.

5. Place the loaded film holder in position.

6. Block the light of the Illuminator with foil.

7. Pull out the film holders dark slide.

8. Briefly remove and replace the foil in the illuminators path to control for exposure.

9. Replace the dark slide with the exposed film indicator facing out.

10. Process exposed film as per developer instructions and enjoy!

Large Format Photomicrography part: II

Preparation of a Ground Glass

Using the integrated camera system II means that one will be correcting for parfocality between the camera and oculars with the shutter assembly optics not the cameras tube length. The process is the same for any of the Bausch & Lomb integrated camera systems and the effect is functionally identical to increasing the cameras tube length. This may not be immediately clear to anyone using the device because on a number of models the adjustment is marked with an “x”. Rest assured that focusing the knob to “15x,” is not going to provide an increase in magnifying power of 15 times over the obdective magnification. Provided this little endeavour is successful, I’ll look into calculating the power of the lens system when in focus. Unfortunately, before any of that a method of obtaining clear focus in the plane of the film will be required. An ideal method of obtaining focus would be inserting a ground glass in place of the film holder. The ground glass would need to be in some type of frame so as to keep the ground surface at the same position the film would occupy. It would at first seen expedient to place a piece of waxed (or oiled) paper onto the camera back and this would work in a pinch. A far better opption would be to cut a sheet of glass to size. If one hasn’t got a sheet of glass to hand a quick trip to the nearest second hand shop or discount store (where a picture frame can be had very economically) will provide the needed material. If one hasn’t got a glass cutter or is not confident in their use of one, a stiff sheet of lexan or transparent acrylic that may be cut with a hand saw will do. If one intends to use glass a finely ground surface may be quickly achieved with a bit of carborundum powder. One must take care to cut the glass to size before grinding. For determining size I have considered two methods. First one may trace out and cut the glass to match the outside dimension, of the plate holder. Alternatively, one may trace the dimensions of a sheet of film and cut to that size. The former is likely the easier option, but if one is careful and has a spare or broken film older the later may prove a more secure and attractive option. In the first case, one will later be supporting the glass with shins to bring it into the film plane. It may be easier in the sense that one may make alterations with little trouble if initial results are not all that one could hope for. Another option would be deconstructing a film holder so that it provides an empty frame into which one may fit the ground glass. Originally sold with a frame supported ground glass, I have never seen a 4×5 body for the Integrated Camera System on the market together with the glass back and feel it likely that most were either broken or lost track of over the years since the apparatus was in active production. It may be worth noting a few points concerning focusing with a ground glass. Focus is limited in sharpness by the fineness to which the glass in question is ground. To obtain an area for perfect focus, one should then cement a cover slip in the center of the ground glass or leave a small area unground. When the clear area is observed using a hand lens or small focusing magnifier one may observe the quality of image that will be captured on film. To leave an area unground one may mask it with a layer of heavy tape (or even a cemented cover slip) which must then be removed after grinding. To grind the glass one need only introduce a little carborundum grit in water to one side of the glass. A second piece of glass (a plain slip works well) is then sanded over the grit under light pressure.

The gallery below demonstrates the process.

Above may be seen my poor abilities in cutting glass, and two ways to go about creating a ground glass for focusing. First a 4×5 piece of glass salvaged from a broken window is inserted into a film holder that had irreparably damaged dark slides. The solid film holders were removed and the glass is supported by the top and bottom of the holder rather than the sides. As an alternative I cut a piece of 1/8th inch acrylic to the size of the film holder. Rather than grind it I simply left in place the frosted protective film on one side. It should be noted that in each case the frosted surface is the one which should be held in the film plane. This means that the in the wooden holder the frosted surface is facing down and in the case of the acrylic it is facing up.

Large Format Photomicrography part: I

Scope and Intent

This series is going to be a bit of a departure from the usual around here, by which I mean that I’ll be covering something I know perishingly little about; namely photography. The practical upshot of which being that I learn something, while the corresponding hazard must necessarily be that I spend a great deal of time, well, screwing up! It’s not even going to be my intent to avoid failure, which can be as enjoyable as success if one has the right attitude. Rather, my goal will be simply to end up with a 4×5 print. I’ll of course shoot for a properly exposed, in focus negative, but in all honesty I fully expect to end up with a blurry, underexposed, wretchedly vignetted negative and an overdeveloped, streaky print if I end up getting that far at all. I’ll claim right now that either way I’ll be throughly enjoying myself. Here’s hoping someone or other out there does as well!

Right, so I’ll be doing an insane amount of referring to R.M. Allen’s monograph Photomicrography I’m sure, anything else is liable as not to be found here or there on the web. I’ll try and link to the sources for the materials and chemistry as they come up and at the end I’ll mock up a quick one-sheet for the practicum and supplies; something without my tedious verbosity! This is apt to be a long one as multi-part series go so don’t be surprised if I toss something else in here or there. All the photos on this site aside, I’ve never really gotten the shutter “bug” and still much prefer an awful little sketch in the margins of my notes to roll after roll (or card after card) of whatever full color high resolution photos I manage to snap. If I ever need a belt of good photography I’ll pop over to Dr. Robert Berdan’s site, see what someone who enjoys it can do!

For this series I’ll be using the BalPlan, and I’ll spare a few lines to say why. I’ve got the equipment to shoot large format on either the BalPlan or the phase contrast DynaZoom, I don’t have the space or the chemistry on hand to process or print color though. It seems a shame to pass up phase contrast, but I just haven’t got a clue how that would look in black & white. The other factor is field flatness. The BalPlan has a full compliment of planachromat objectives; just the thing for a 4×5 negative right? Maybe not though, how much of the visible field transfers to the negative, would spherical aberration be noticeable if I used an apochromat, a fluorite?

Once I end up with a negative I’ll process it. I haven’t got a dark room, and can’t be bothered to take over even my own bathroom for the purpose, so drum processing it is! Then I’ll try and contact print it onto some very slow paper and drum process that. I’ll try not to act like I know what I’m doing (because I don’t) and I’ll look at how to rig something up from available materials so anyone with the photography resources (but maybe not the same microscope collection) can maybe get something out of this.

Opaque Object Microscopy part: IV

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This last installment will be a look at the B&L STM Electroplater’s Microscope. A refinement on the Standard Teaching line, this Metallurgical microscope is designed for simplicity and easy of use. Superficially it resembles any of the other stands of the ST line, enamel grey with an integral, two-position nose piece, it manages to provide all that is needed and nothing that is not. A single intensity transformer powers a Nicholas style light source that is fixed to the side of the stand just above the nose piece. The light path features a filter holder but is not equipped with either field or aperture diaphragm, rather the light path is permanently restricted to a degree appropriate for the two supplied objectives.

3ca50003-f562-435a-95e7-fbda76ccfc37-649-000000960bbb8e15_fileEach objective is of 215mm tube length construction and is corrected for use without any cover glass. One is a low power finder (5x) and the other a higher power (40x). One will quickly notice that neither is of the power one expects to find on a student microscope; 10x and 43x being the usual combination. The reason for this quickly becomes apparent when one calculates powers in consideration of the characteristics of the stand. A 215mm tube length, correction for no cover glass and the nessecity of a short working distance. At right one may see the working distance of the 40x objective.

In place of a standard eyepiece it features a filar micrometer ocular as for most all metallurgical work one would desire the ability to take measurements. In that same vein the fine focus adjustment is graduated as well. Although the stand features an inclination joint, there is no adjustment for the stage and no arrangement to provide for transmitted light work. Internally, the light source is directed downwards by a half silver mirror which is not adjustable without tools. This was no doubt done so that it may be aligned once and may then be employed without a further thought to the matter. When I first acquired this stand the reflector was shattered. No matter, it was easily replaced and enabled me to have this delightful little stand for no more than $40 USD plus shipping!

In the interest of providing a little eye-candy I placed the seemingly polished brass surface of a pocket knife in a bit of putty on the stage. Putty or a specimen holder of the standard sort is recommended for most specimens for the sake of stability. A photomicrographic ocular of 7x power and a Pentax microscope camera adapter was used to take the photomicrographs.

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Pentax Microscope adapter in place on STM Electroplater’s Microscope

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Low Power

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High Power

In the above images we may observe the compromises made in the STM Electroplater’s Microscope. The low power photomicrograph shows that the apperture size employed in the illumination system is such that slightly less than the entire field is evenly illuminated. In normal visual use with the 10x filar micrometer eyepiece this is only very slightly noticeable. The 7x photomicrographic eyepiece exaggerates the defect because of the larger field of view it provides. It would be possible to artificially crop out the uneven area by using a greater photomicrographic tube extension, but the one I use is perfectly sized as to be parfocal with the eyepieces when employed on a trinocular stand.

In the high power image we will immediately notice how the curved portion of the specimen surface falls out of focus and quickly devolves into a mess of chromatic aberration. This is why flat surface polishing is such an important part of metallurgical microscopy! Luckily enough, the (exceedingly self-congratulatory) microscopist managed to place the specimen such that the two larger scratches (dark marks slightly left of center in the low power photomicrograph) remained in the frame under the higher power objective. Note how the formerly dark high contrast scratches are now fully illuminated and visually interesting.

Next time: Adventures in Large Format Photomicrography! -K

Significant B&L Library Update

As the result of a thoughtful donation by an excellent person who I won’t embarrass by naming outright, the B&L library will shortly be doubling in size. I’ll be doing my best to get as many of the new materials as I am able to scanned and uploaded in the coming days. Some of the materials have already been added, eight new documents as of last evening. With so many more documents available, and so many more to come, I’ve put a little (regrettably very little) effort into making the library page a bit more attractive. Gone are the clunky columns of cover and download link! Now each document is merely a cover, that cover linking of course to the corresponding document. While at some point I may look into putting them into some sort of order, I have no planes to attempt that now.

By far the primary use of these documents, at least for myself, is in properly identifying a stand or component so that it may be restored and used appropriately. I have on occasion made use of them in that capacity while assisting others in identifying just what they have, or what they may be considering for purchase. At the very least they are an aid in determining the completeness of an apparatus or compatibility of a component. I won’t pretend to know how they are used by the many people who download them, I’m simply happy to share with anyone who may need them all the free Bausch & Lomb puff manuals and guides which I have been fortunate enough to have at my disposal.

Opaque Object Microscopy part: II

Before looking closely at microscopes which were purpose built for reflected light work it is first imperative that one understands the requirements of such a stand. It must of course allow for some means of illumination, but beyond that there are a few needs that are not so obvious. Consider the compound transmitted light microscope, several aspects of it’s construction are dictated by the optical properties of human vision, a substantial number of others are dictated around changeable constants that are functionally arbitrary. A microscope slide and cover slip that is of a given thickness greatly simplifies the construction of an optical system that will provide an ideal image with minimal and known defects. Furthermore, it dictates that all specimens will be of a consistent and narrowly variable thickness.

Any microscope that needs to accommodate opaque objects will either have to account for the need to examine specimens of unknown thickness or be considered specialized. It need not be overly complex, one could make use of a stand having a significant range of motion in its coarse focus, or possessing a means of modifying its base working distance-as one finds on many stereo microscopes.. A further option would be to articulate the stage such that it may further enlarge the accommodation of the coarse focus. This is a simple mechanical alteration to an otherwise standard microscope foot; as a condenser is unnecessary, the stage is for all intents and purposes mounted to the condenser mount. An inverted microscope forgoes this need entirely by radically re-configuring the entire apparatus, a good investment if only one microscope is liable to be acquired, but it’s worth noting that inverted microscopes are in general far less common on the second hand market and consistently more expensive.

It is also required that the microscope provide for the specialized optics of a reflected light system, namely the light source. In the initial post we saw the difficulty of using a light source external to the image forming optical axis. It is therefore required that the illumination system be congruent with the optical axis. This requires that there will be some additional apparatus placed somewhere in the optical axis, by convention it is generally placed outside of the body, between the nose-piece and the end of the body tube. Whether this is dictated by optics rather than mechanics (or the economics of manufacturing) is unimportant, the result is the same.

At a point in the optical column of the microscope a high intensity light source is introduced. In every example of which I am aware this light source is situated perpendicular to the axis. It is suitably condensed and often fitted with a pair of iris diaphragms (a field diaphragm and condenser diaphragm) as well as filter carrier before being directed down towards the objective via a reflecting surface. A prism or half silver mirror is the usual method; often both are available with the ideal choice being contingent upon specimen and objective.

The actual construction of the reflector is related to the properties of the objective, with all parts involved being of a number of mechanical types. All of the differences in the system of illumination are chiefly concerned with the path of light. There exist two primary types: coaxial and vertical. It’s confusing because few operators, and even manufacturers are careful with their terminology.

Both coaxial and vertical illumination are methods of reflected light microscopy, and coaxial is by definition vertical while vertical is not necessarily coaxial. Coaxial illumination is so called because the path of the light source shares its axis with the path of the image forming rays. The poor mans coaxial illuminator is a flashlight held to one eyepiece of a binocular stand while the other is used for viewing-authors note: don’t do it! The axis of illumination and image formation are one and the same. Vertical illumination is a story of two axes where each is distinct but parallel. The most common type of vertical illuminator is able to provide both methods, but the quality of the coaxial illumination is often inferior when compared to modern outfits designed for coaxial illumination.

Without bothering to get in to dark-field (yes, there are dark field objectives for reflected light work) there are two types of objective one will encounter. The first is essentially no different from any standard objective, excepting of course for differences in the common powers, corrections, and other properties best left for later. The second, and more complex type, is designed to work with a particular type of light source. This second type (which I have always thought of as metallurgical as that is how the BalPlan microscope line of B&L designated them and they were the first I used) caries within its body a transparent glass bushing which extends from the mount to the object lens, surrounding totally and supporting the lenses of the objective. This glass pipe is little more than a means of placing a ring of evenly diffused light on the specimen in a place where the objective itself would obscure other sources. Properly arranged, it is an excellent system and dispenses with much of the glare one will find in poorly aligned coaxial or even vertical systems.

There, next time: photos! -K

Opaque Object Microscopy part: I

I think at this point I’ve been away long enough that this may qualify more as a return from the dead than a return from a hiatus. -K
Most of what anyone at the level of a hobbyist is going to be looking at with a microscope is going to be what is convenient. Now, this is not meant as an indictment, merely a truthful commentary. For the bulk of those with a microscope this is going to mean that what one is going to be looking at is dictated first, by the microscope which is available, and only after by ones interest. When conditions allow this translates to transparent objects for the compound microscope and large opaque objects for the stereo microscope. There are, thankfully, limitless opportunities for the indulgence of ones interest regardless of the microscope which is available.

The next few posts will focus on a category of microscope which is rather less common but is specialized for a particular variety of specimen. The particular type of microscope is rather less common, and one could speculate endlessly on the reasons for this. This microscopist is of the opinion that the reason for this is in general attributable to its being far harder to prepare specimens for a reflected light microscope, than to settle for lower magnification and use a stereo microscope. However, there are a variety of applications for which one will find the power of a stereo microscope lacking. One is then left with the prospect of attempting to so treat the specimen as to render it suitable for transmitted light microscopy, or of finding some way of providing suitable lighting and using a standard compound microscope. Anyone who has attempted to observe an opaque object at high power will understand the difficulty of providing for adequate illumination.

For the sake of completeness, here are the logistics when one is forced to make use of a standard compound light microscope for reflected light work. One might first make use of some small and high intensity light source, employing it in such a way that the termination of the visual optical axis is brightly lit. This is actually surprisingly simple in the present day when an LED flashlight the size of a shotgun cartridge is brighter than any oil lamp. After oil lamps gave way to electric lamps the microscopist was required to somehow retrofit a standard lamp bulb so that it would provide a bright beam of light with no errant brightness.

There was also the possibility of purchasing a small bright light source such as a Nicholas lamp. Although those were surprisingly expensive in their day, they are quite economical now and widely available second hand provided one is willing to type a few searches. Before getting to much farther off topic, do consider picking up a Nicholas illuminator. Color temperature aside, the tight beam is well corrected and the arm most are fitted with is a great asset. Working with a Nicholas lamp and a compound microscope, we will quickly see why this method is far from ideal.

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Poorly set up.

In the above image we can see that a light source is set up sufficient to permit the specimen (here the engraved body of a pocket knife) to be brightly illuminated to the naked eye. There is enough working distance that no significant difficulty was involved in setting it up. A quick look through the eyepieces will immediately demonstrate that this set up is not only far from ideal, but entirely unsuitable. The light source is a painfully bright halogen bulb but the view from the oculars is quite dim, contrast is excessive, and there are visible color fringes even though the lowest powered objective (here a 30mm EF/3.5x achromat) is being employed. Some of these defects can be corrected even in this compromise set up.

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Ideal compromise set up.

In the above image is shown an exaggerated ideal arrangement of the available resources. If one takes the stage for a plain, and draws a vertical line along the visual optical axis the light from the illuminator should be arranged so as to be as at the most acute angle to the optical axis possible. This will go a long way to limiting the extremes of contrast and removing the color fringes. It will similarly  render the specimen as bright as possible under the present conditions.

It may not be immediately apparent but working distance is the limiting factor here. As soon as one moves beyond the 10mm or so that one is afforded by a standard 16mm (10x if you’re more comfortable with magnification than equivalent focus) objective the few working distance of a 4mm (43x) objective is far to short, even that of a rather less common 8mm (21x) objective will be much to short for all but the most intrepid of operators. Then, should illumination be secure one will be presented with a view of such poor quality that the effort is entirely wasted.

Next up… vertical illumination.

Why Dehydration is Important

One of the basic tennants of mounting in resinous media is dehydration. Whatever water a specimen contains must be removed prior to mounting. The dehydration could be acomplished by evaporation in air, via a series of displacements in alcohol, or foregone by virtue of beginning with a dry material such as paper or hair. The process of dehydration itself is straight forward enough that it’s hard to screw up when applied to much of what a novice is apt to be mounting, but it can happen. Let’s take a look at the effect of excess water on a resinous mounting media.

Whole mount without pressure.

In this example a whole Blaptica dubia cockroach (2nd instar) was killed just after moulting and mounted without pressure in natural Canada balsam. The specimen was cleared in turpentine but not dehydrated with an alcohol series or with any other method. It was cured for some few weeks on a low temperture warming table.
Right away one can tell that something is not right with the slide. The balsam has yellowed as is to be expected with a whole mount of this sort but some smudge appears surrounding the specimen. From the photo it may be hard to tell but that smudge is not on the outer surface of the coverslip, it’s on the inside. Visually the defect appears quite minor. Observed under even the slightest magnification it soon becomes clear that the view will never be, clear, that is.

With c-mount camera and 4x objective on BalPlan microscope.

What has happend is obvious. The moisture that remained in the specimen was greater than could be diffused into the mountant. Of all resinous mountants natural Canada balsam is the most forgiving. Balsam can often diffuse a bit of excess water, but in this case there was just too much. All that water was forced from the specimen as it was slowly displaced by the mountant. Because the displacing mountant is significantly more dense than water, the water is forced against the underside of the cover.
A problem like this is at its most extreme in a whole mount without pressure. In a thin section the water will tend to be, well, thinner. They might be thin enough that one could imagine focusing below them to optically section the specimen and still get some use from the mount. Sadly, the significant difference in refractive index will prevent focusing through the water dropletts under any circumstances. Let this example serve as a warning to every mounter, proper and complete (or nearly so) dehydration is a must with resinous media.