Troubleshooting
The most common problems encountered with the Nikon Digital Sight camera system are reviewed in this section. Suggestions for solutions are also included, but many imaging problems may arise in the microscope optical or illumination system itself. Be sure to check both the camera system and the microscope when difficulties occur.
Problem: Acquired images are too small.
Solution: Three image sizes are available for selection using the File Setting panel of the setup menu, as described in the Saving Digital Images section. Make certain that the desired image size is selected.
Problem: Acquired images have low resolution.
Solution: Images may be saved in either the JPEG or Bitmap format. If the JPEG format is selected, then the JPEG quality may be set too low. Try increasing the JPEG quality in the File Setting panel of the Setup menu, as described in the Saving Digital Images section.
Problem: Images are not sharp.
Solution: Check the microscope focus to obtain a clear, crisp image on both the monitor and through the eyepieces. Focus problems most often occur when the camera system is not properly mounted on the microscope trinocular observation port or when it is not parfocal with the eyepieces. Check that the camera is properly inserted into the microscope's vertical tube, and that the camera has been properly secured with the clamping screws provided on the vertical tube. To avoid excessive vibration, which can lead to severe focusing problems, mount the microscope on a sturdy bench or table that is placed on a flat, level, and solid floor. It is often wise to utilize vibration-isolation equipment in environments that are prone to building, ventilation, or traffic vibrations. In rare instances, poor focus can be due to an excessively small substage condenser aperture opening size. Check the size by examining the objective rear focal plane using a phase telescope or Bertrand lens. If the image has been enlarged too many times by the microscope optics, empty magnification can occur that leads to "soft" images. Always restrict the magnification factor to a value between 500 and 1000 times the numerical aperture of the objective. Setting the sharpness on the camera control unit can also help to sharpen the image, as described in the Image Correction Features section.
Problem: The image is too dark or too bright.
Solution: This error often occurs when the exposure time is set too high or too low, or the camera gain (sensitivity) is not correctly adjusted. Check the microscope illumination to ensure the viewfield is bright and the proper amount of light is entering the camera tube. Check the exposure level indicator in the CAM menu to determine if the image is underexposed or overexposed.
Problem: Images display poor color balance.
Solution: The most common cause of this error is due to the color temperature of the microscope illumination system. To remedy the situation, insert a color conversion filter to bring tungsten-halide illumination to daylight color temperature levels (5500 K), and set the illumination voltage at the predetermined optimal level for the microscope during photomicrography. Another cause might be an improperly specified white balance with the camera control unit. Use the Digital Sight's White Balance feature to adjust white balance, as indicated in the White Balance Calibration section. If these solutions do not solve the problem, check the monitor to determine if the color adjustment is improperly set.
Problem: Image contrast is low.
Solution: This is a common problem in optical microscopy, regardless of whether digital imaging or photomicrography on traditional film is being conducted. The cause is often an excessively large setting for the field or aperture diaphragms. Adjust the microscope for proper Köhler illumination and examine the field diaphragm to determine that it circumscribes the field of view. Remove the eyepiece (or insert a Bertrand lens) and examine the rear focal plane of the objective to observe the size of the substage condenser iris aperture diaphragm. Adjust this diaphragm so that it is approximately 70 to 80 percent of the objective numerical aperture or exit pupil.
The utilization of improperly configured optical systems can limit contrast, especially when conducting image-enhancement techniques such as phase contrast, differential interference contrast, or Hoffman modulation contrast. Carefully check the microscope and examine the specimen through the eyepieces to determine if these techniques are providing adequate contrast. In general, to improve the contrast of a monochrome image, insert a green interference filter into the light path at some location below the substage condenser.
Other causes of poor contrast are intruding ambient light and low inherent specimen contrast. Turn off the room lights to see if the situation improves, and place a high-contrast specimen on the microscope stage to test for contrast improvement in the Digital Sight camera control unit hardware.
Problem: The system clock is not keeping time.
Solution: If the system is not used for an extended period of time, then the date and time backup function deteriorates and the clock stops. Simply reset the correct date and time using the Additional Settings panel of the Setup menu.
If you encounter problems that are not addressed here, please send us an email so that we can analyze the problem and possibly offer a solution.
Contributing Authors
Matthew J. Parry-Hill, Thomas J. Fellers, and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.
