Setting a Nikon CoolPix 990-995
by Aaron Messing
Originally posted to sci.techniques.microscopy on 10/31/02 updated 11/18/02

In the discussions concerning the use of the Coolpix for photography with a microscope, several different combinations of settings have been put forth.

I have used the CP990 extensively and found the following settings to be very productive for me. They were recommended by Nikon.  The reasoning for these choices are discussed by Roost and Oldfield in their book.  The principles are the same for using 35mm cameras that are fitted with a front lens.

1. Set the camera's exposure program to the "Fixed  Aperture" program. On the CP990 it is the "A" program.  This allows the Coolpix light-meter to set the shutter speed for the correct exposure.

2. Set the aperture to the largest opening (lowest  f-stop number) manually.  Note: On the CP 990 the aperture is setting is connected to the zoom setting. As the zoom is changed to the higher magnifications the aperture is automatically decreased (higher f-stop numbers). Therefore the aperture needs to be checked just before the shutter is released, especially if the zoom range has been altered since the aperture was set.  Closing down the camera aperture in this application will not increase the depth of field.  It will cause vignetting.

3. Set the camera focus to infinity.  This is a manual control on the camera that is identified with an icon picturing mountains.  The icon appears on the LCD with other indications of the settings.  Invoking this setting causes the auto-focus to become inactive.  If you do not see that icon the auto focus will run to the detriment of the image. All focusing is accomplished with the focus controls on the microscope.    N.B. I have found that trying to use the camera's auto-focus is useless because it continually hunts for a focus and never finds a stable setting.  The lens is especially apt to move in the instant that you release the shutter.  The reason is that a single focus through the microscope does not exist. When using a microscope by eye we invariably are changing the focus to see up and down through the specimen.  THE FOCUS is a subjective choice within a narrow range that is more or less in focus.

4. Set the flash to inactive (off).  If the flash goes off the shutter speed will be wrong as the camera will try to adjust for the extra light the flash gives off.  Of course the flash cannot reach the subject so the image is very underexposed.

5. For standard bright field I use the incandescent setting to control the white balance with a standard halogen light source.

6. I try to avoid using the zoom to increase magnification.  I use it to fill the corners of the image. However at the higher zoom settings I find the images suffer from fuzziness and poor color correction.