Projection Microscopy III

The Set Up

The 1 Inch is old enough to be corrected for a 10 inch tube length so when setting up for micro-projection one must be sure of two things; first, that if an eyepiece is used that the draw tube is able to provide for that distance, and second, that the projection distance is measured from a point 10 inches beyond the rear lens of the objective if an eyepiece is not used. For simplicity a dedicated projection microscope will be used for testing. It is a Bausch & Lomb dating to 1956 and was intended for use with its own projection objectives (distinct for the orientation of the B&L logo on the objective barrel). The intensely bright lamp integral to the stand will have no difficulty providing adequate light.

According to published information from the manufacturer contemporary to The 1 Inch, one knows that a minimum projection distance of 15 feet is recommended for the most highly corrected image. A projection surface (in this instance a handy, blank, artists canvas) was positioned 16 feet from the stage of the projection microscope. With the head of the microscope properly aligned a projection distance of just over 15 feet was obtained.

Results

It’s would appear that obtaining a digital photograph of a projected image is not a job to be entered into lightly or in haste. Apologies then, but please understand that in person the image produced by the objective is in a word: astounding.

Stained section of human skin

Stained section of human skin.

Palp of wolf spider mounted whole with pressure.

Palp of wolf spider mounted whole with pressure.

The low light conditions and poor handling of the same by the author and his 14 year old digital camera do such little justice I considered not including the images at all. For several hours (until other responsibilities intruded) various specimens demanded projection and rapt attention. During this time there was no noticeable heating of the objective despite the intense heat of the lamp. In fact having previously made use of the objectives provided with the stand I can say that The 1 Inch remains cooler than those of much more modern construction.

Color correction is as better than that provided by any objective alone that I have seen. In spite of the long projection distance flatness of field was observed to be quite profound. Using a wall as the projection surface, images spanning 5 feet were observed to be in nearly uniform focus across their entire diameter.

I will have to read up on low-light photography in the hopes of sharing more accurate portrayals of the abilities of The 1 Inch. -K

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