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Helpful Photography Hints: Page 2

There are many film types available for photomicrography. Choose the film type based on the following details:

The ability to reproduce the colors of your image that you are trying to capture is important. Thus, the film often used is 35-mm color slide film due to the convenience of handling, transporting and filming.

Professional photographers frequently use black and white prints or slide transparencies. Slide film and black and white film are more difficult to use, but the images are sharper and contrast is slightly better than color negative prints. The developing process today is usually done by machines, and automatically adjusts for slight errors or imperfections. Color negative prints are also cheaper and more easily developed, reprinted and blown up. Slides and black and white prints typically take longer to develop commercially.

Special 35-mm films are available for use in photographing in  areas with tungsten illumination. If a  tungsten light source is combined with a camera using tungsten-balanced film, then additional filters may not be needed for acceptable photo images. Film sold as daylight film can be used successfully in photography if the illumination has been adjusted. If you are filming in a room that is lit by fluorescent lighting, make sure that the color balance is not changed.

All films are labeled with a speed rating or ISO/ASA speed. Film speed is a measure of the film's sensitivity to light. The lower the ISO/ASA number, the slower the speed of the film and more light is necessary for correct exposure. Higher speed films, (400-1600) will require less light for proper exposure. Higher speeds will capture fast moving images more easily, but the quality of the image will be grainier, and fine edges will be fuzzier, especially if an enlargement is desired. Higher speed films allow the use of higher shutter speeds and/or smaller apertures than do lower speed films. Use the film speed that you can correctly capture the image you need. If you do not plan to enlarge the images, 400 or 800 speed film will be easier to use.

Different brands of films will result in minor color variations. Kodak tends to give warmer colors, Fuji film results in sharper, brighter, images, especially greens. For images using dark field and for capture of fast motion of higher life forms, 400-800 or higher speed is recommended. Use the same film if you get results that you like with images you take.

When turning in film for processing, make a note to "Develop as is. Do not adjust color." Many photo labs do not know what the image is supposed to look like and may try to make corrective adjustments. Many times film is now developed on huge machines that will try to automatically correct images that it assumes are incorrect. Ask them to turn off auto correct for your rolls of film. Technically, no adjustments should be made on the negatives. All adjustments should be made on the cameras and your lighting  long before the photo image is taken.

Many factors may affect the color balance of photographs. Filters, which transmit some colors and absorb others, can be used to facilitate the transmittance of needed color contrasts. This is more important with black and white film. Temperatures relating to film storage and temperatures at the time of exposure will affect the photomicrograph. Film should be stored at less than 10°C (50°F) to extend the film shelf life. Filter suggestion and temperature exposure ranges are discussed in the information sheets supplied with the film. Color corrections can also be made in the dark room but try to stick to creating the image you want with your microscope, the camera lighting, speeds and apertures instead and you will get better results. The less you have to do later on, the easier it will be to take pictures  and less of a hassle.

Where you have the photos developed also will affect the quality of the picture. Many labs may vary slightly on the quality of the final print received. This can be due to minor variations in the amount of developing time, the equipment, chemicals or the developing paper that they use. The key to developing good photos is to find a film processor who will produce consistently high quality prints. Different paper can be used, some use Fugi and some use Kodak. Some use slightly different chemicals. The same image can look slightly different also if printed on glossy paper vs. matte. Play around with these variables, find what you like and then stick with it. The whole purpose of taking photographs is to capture a moment in time, an image that you want to remember or share with other people.

Determining Exposure

Before taking a picture, the correct exposure must be determined. This depends on the nature of the camera, the type and intensity of illumination and numerous other factors dealing with color balancing. The weather, lighting and movement of your subject can also impact clarity of a final image.

Two things on most 35-mm cameras now determine exposure. A combination of shutter speed and F-stop (or aperture) will determine depth of field and how much light is needed.

Shutter speed determines how long the camera shutter is open. With a faster or higher the number (1000 is really 1/1000 of a second) there will be very little depth of field but it will freeze or stop action. Slower shutter speeds at 1/30 and 1/15 will have more depth of field but are not very good for freezing motion.

Aperture or F-stop determines how wide the camera iris is opened. Smaller numbers f2-f16 let in more light. Larger numbers let in less. If low light conditions exist, as when photographing at high magnifications or if the field of view is dark, the shutter speed should be reduced (slowed down) and the aperture decreased to provide more exposure time for the film. A faster shutter speed is used when high light conditions are available. Also, the faster the shutter is opened and closed, the less a moving object will blur. Minimizing movement and blurred images is difficult, but can be achieved through the use of immobilizing agents.

The appropriate exposure time can be determined only by making an exposure series or by using an exposure meter. Most automatic 35-mm cameras have these built in. Selecting the proper exposure should be done methodically and should be fully detailed. Records must be kept of a trial run. A log form would list the film type and speed, microscope, objective, camera settings, slide or print number, light intensity setting, notes on specimen preparation, filters, magnification and development time (if applicable). Once the slides or prints have been developed, the records can be reviewed to match the slide or print number of the optimum acceptable images to their appropriate record entries. These entry values should then be used for future photomicrography work.

Some cameras have programs built in. These make it easier to capture the correct photo. The automatic cameras read and sense the light and adjust the correct exposure for you making it easier to always get a good photo. Read your manual and make sure you have your setting on automatic.

Most photographs tend to be underexposed. A good rule of thumb is to expose most photographs longer than normal photos on average.  To adjust for this, use a longer exposure, larger aperture on the camera, or slower shutter speed. On some cameras, there is a correction setting or exposure compensation dial that can be adjusted for this. Usually -1 or -2 should work. The exposure compensation should be in the negative numbers when shooting in dark settings and on the positive side when viewing subjects in bright settings. Check individual camera manuals for variations. Different exposure compensation is also necessary depending upon the ASA speed of film used.

Bracketing is a technique that also can be used on adjustable cameras. This is where the same picture is purposely under and over exposed one to two f-stops different than the suggested camera meter reading in order for the perfect picture to be taken. These are tips that are used to get phenomenal pictures with correct shadows, lighting etc.  The main thing that is critical is that you find out best what your equipment does and do the same thing always. You can play and explore when you are trying to take pictures.

For more information- Film Speed and Filters

Copyright © 2002 Creative Captures. All rights reserved.
Revised: 11/03/04.