التصوير الفوتوغرافي المجهري -١- مجلة فن التصوير اللبنانية _ ع٣١

Microscopic photography -1-

Microscopic photography is an accurate specialist facility in the world of photography, and we present it here in two episodes.

With the world of the microscope or the microscope, cameras enter a special and distinguished field of specialized photography, which is microscopic photography. And her huge microscope. Diafoot, but before talking about it, it is necessary to preface by talking about ordinary microscopy first, provided that we follow up in another episode with “Diavote - Nikon.”
The microscope offers a whole new field of images for the camera to capture, and despite the complexity of some of the more advanced methods, basic photographic microscopy remains within the reach of the non-professional photographer.

However, the image quality is at its best when using microscope optics alone. Therefore, it is always advisable to decorate the camera lens before using an adapter to connect the camera to the eyepiece. A single-lens reflex camera is ideal for this work, as long as it allows operating the microscope and imaging through it with the same eyepiece. If the light meter through the lens works without the lens attached, it will allow This is by taking direct exposure readings.
The main lens in a modern microscope is the objective lens (*), i.e. the closest lens
to the sample, and the subject lenses concerned with flats *) despite their high price, give a sharp prominence from edge to edge. It should be noted here that the two most important features of the subject lens are its magnification and the power of its dissolution. 100 (X), however, the total magnification is increased by means of the eye lens (*), which enlarges the image after it was originally produced by the subject’s lens, and to a range between 5 (X) and 25 (X) as well.

As for the dissolution energy, it depends on the numerical aperture, or (N.A.) of the subject lens, and this is a measure of the ability of the subject lens to distinguish fine details, that value usually does not exceed 100. There are special lenses designed to work immersed in oil, and they have larger numerical apertures and dissolution energy Better - if we use a large zoom with a subject lens with a lower numerical aperture. All we will achieve is an empty enlargement.” - As a rough guide, we find that multiplying the numerical aperture by 1000 will give the maximum magnification that can be worked with.

As for the third part of the optical apparatus, after the lens of the subject and the lens of the eye, it is the condenser of the middle stage (*), which is used to focus the light, and there is a diaphragm for the aperture that also works to adjust the scale of the light beam. In some microscopes, there is an adjustable mirror that directs the light through the condenser through an external source, but many modern microscopes have their own light source.
As for the normal lighting for microscopic photography, it is tungsten, with a color temperature ranging between 2700 degrees (K) and 3200 degrees (K). Halogen tungsten lamps are the most stable. It should be noted that the typical microscope lamp has a lens and a field diaphragm (*) that adjust the beam. To photograph moving objects, we will need an electronic flash. This means that an additional tungsten lamp will be needed to focus and adjust the content.

Camera setup:

Anyone can set up the camera in the following way: You connect your camera over the eye lens using an adapter that you get from the camera manufacturer. As for the basic lighting method, it is the illumination of a radiant field, and it is important to fix the light source in the center, and focus it so that the illumination is uniform over the entire image area. It is a measure that can be accomplished by focusing the image of the lamp filament on the condenser.
As for the exposure, it is difficult for you to reach the appropriate exposure the first time, and you have to plan a series of tests, even if you are able to use the camera meter through this lens, and you have to adjust the exposure with a zero density filter instead of doing that by adjusting the shutter speed, not Then also test different combinations of eye lens and subject lens, then to reduce the risk of shake, lock the camera mirror before each exposure, and work with a pickup wire.

Most ordinary films can be used for microscopy photography, but given the importance of resolution of fine details, you have to choose a fine-grained photosensitizer and it is a hassle to
Most subjects under the microscope lack optical contrast.
There is now a film designed for photographic microscopy - Kodak's color film for photographic microscopy.
( Kodak Photomicrography . Color Film .2483 )
Combining ultra-fine graininess with ultra-strong light contrast, it's perfect.

- samples

You can buy samples of different types of subjects mounted in microscopic slides from specialized funders, but you can also prepare them automatically. It is worth noting that most of the samples are either very thin tissue sections, scanned materials, or chemical crystals.
While you can simply prepare chemical crystals. And by allowing a drop of solution to dissolve on a glass slide when you have finished preparing the samples on the slide. You can make it permanent by sticking a cover glass over it

Other types of lighting

Some samples, such as aquatic life species, can be seen with greater clarity if they are illuminated by liquid rays, and it is not possible to illuminate non-transparent samples except in this way. The dark-field anisotropy (*) uses direct light waves and a dark background. As for the normal way to achieve this type of illumination, it is based on the use of an opaque field pause that works effectively to transform the circle of light that is directed upwards from the mirror into a ring. The amount of light is large, and it makes color photography difficult.
Polarized illumination (*) can reveal new features in some samples, and the resulting colors can be characterized by amazing vitality.
Here, two polarizing filters are used, one under the condenser - called the polarizer - and the other directly under the eye lens - called the analyzer - the polarizer works to pass the oscillating light waves in one plane only. If the sample has polarizing advantages, it will split the light into two contents. One is slightly slower than the other by rotating the analyzer. You can make these two contents overlap, creating new colors.
Phase contrast microscopes (*) and interferometric contrast microscopes work as a principle
Polarizer - it divides light into two rays that travel at different speeds to some extent, and this is done
Through perforations resembling rings, or semi-transparent sheets, or prismatic lenses, and by making the two rays overlap one with the other, so that almost transparent details appear from the samples.

A - microscope

The microscope enlarges the image in two stages. The first is magnification that comes from the lens of the subject located close to the sample, and on this lens is an indication of its magnification power, which ranges between 4× and 100× (× means double). Then the first image projected by the lens of the subject is enlarged again, by means of the lens of the eye. These, in turn, have an indication of their magnification power, which ranges between 5× and 20×. As for the overall magnification that the eye sees, it is the product of multiplying the magnification of the subject’s lens by the magnification of the eye’s lens. An example of this is the magnification of 20× from the objective lens and 10× from the eye lens, so the overall magnification becomes 200×.
With regard to photography, we find that the camera link has a very great value, as it provides adjustments to the focus and the fixed link, then with the removal of the camera lens, the enlarged image coming from the eye lens becomes displayed on the flat film, and when the shift is made from the optical focus to the camera focus, some adjustments become Necessary - Either the lens of the eye should be raised to a higher location, or the lens of the subject should be focused while it is farther from the sample.

Set up the microscope
Here are the main steps in this field, although in the practical field, there is often a need for continuous re-modification, as long as one modification often affects other sites, and the necessity requires considerable training.

1- If the lamp is separate, we have to place it about ten inches (25 centimeters) away from the microscope, and adjust it so that the light is focused on the woman.
2- Adjust the mirror so that the light is focused on the pupil of the sub-stage condenser.
3- The narrowing of the diaphragm of the field on the lamp with the focus of the condenser until the shading of the diaphragm becomes sharp.
4- Expanding the diaphragm of the field, so that its edges are outside the image area directly.
The lighting is now correct
5- Focusing the sample with the sample lens in the microscope
6- Remove the lens of the eye, and look directly into the tube, where the aperture of the diaphragm adjusts until it reaches about 4/5 of the bright circle that we can see.
This reduces flare to a minimum and brings the subject lens to its maximum resolving power.
Prepared by Dr. Mahmoud Al-Houbi