Another very important capability of the Coolpix 990, 995, and 4500 model series is the ability to be used in macro mode with a minimum field width of 21-mm, for my Coolpix 995.  The threaded bushing containing the 8X WHK eyepiece can be quickly unscrewed from the adapter, as shown in Figure 11, so that the camera can be mounted on a monopod while retaining the cable release feature of the adapter.  The flat base of the adapter has a ¼”-20 threaded hole for attaching to the monopod or tripod shown in Figure 7.

click image to enlarge (173K) Figure 11

click image to enlarge (249K) Figure 12

This final section is for those interested in how the threads were lathe cut for the connection between the bushing and flat base.  Lathe cutting of threads is a procedure most home machinists try to avoid.  The bushing has only a short section of threads ending at a shoulder.  This makes an accidental and disastrous collision of the cutting tool with the shoulder very likely.  The quick change gear box on my Wade lathe makes the setup time for the threading operation minimal compared with the time which would be required for machining a mounting flange on the end of the bushing and locating and tapping the holes screws through the flange into the flat base.  The solution to the risk of collision with the shoulder has been known for a long time and generally ignored because it is not a method used by production machinists.  One solution, discovered by others, is to disengage the motor drive and drive the lathe with a hand crank as shown in Figure 12.  This photo shows an adjustable stop for the carriage to prevent cutting into the shoulder at the ends of the threads.  This would not be safe to use under conventional threading with the motor drive because the gear drive could be damaged if the half nut was not disengaged just before the carriage reached the stop.  The hand drive with the crank allows adaptive control of the loading on the crank as the carriage reaches the stop.  The cutting tool is backed out of the threads and the crank rotation reversed after the stop is reached.  The half nut on the lead screw is left engaged until the threading operation is completed.  This avoids the mistake of not engaging the half nut at the proper setting of the threading dial, and actually speeds up the process.  Figure 13 shows the cutting tool engaged in the threads with an adjustable stop for the cross slide to allow quick and accurate return to the same setting before taking the next threading pass after moving the 60 degree included angle cutting point inward with a small increment of feed from the compound set at a 29 or 30 degree angle.  This is shown close-up in Figure 14.  A thread pitch of 40 threads per inch was chosen for the adapter.  Cutting of the mating internal threads in the flat base is shown in Figures 15 and 16.  The cutting point for this operation is set in the end of a boring bar.

click image to enlarge (280K) Figure 13

click image to enlarge (243K) Figure 14

click image to enlarge (265K) Figure 15

click image to enlarge (276K) Figure 16

My Wade lathe cannot cut metric pitch threads.  The Coolpix lens filter threads have a pitch of  0.75-mm. I can cut metric threads with my modified Unimat miniature lathe.  I had to cut the 0.75-mm pitch threads in the cover cap for the Zeiss Kpl eyepiece using the Unimat system.  I also use a hand crank to drive the Unimat spindle for thread cutting.  The Unimat uses an unusual method of cutting threads without a geared lead screw used on conventional lathes like my Wade lathe.  A thread pattern attaches to the spindle behind the work-holding chuck.  The cutting tool with its cutting depth control mechanism is mounted on a sliding rod along with a brass follower, which engages with the thread pattern behind the chuck as shown in Figure 17.  Threading the cover cap for the Zeiss eyepiece to fit the Coolpix threads required first making a mandrel with 0.5-mm pitch threads to mate with the internal threads of the cap.  This threaded mandrel is shown in Figure 18 while it is being centered in the four-jaw chuck before the cap is installed on it for external threading.  Figure 19 shows the external threads being cut into the cap.  The Zeiss adapter is shown fitted to my Coolpix 995 in Figure 20.   The time to do the threading of the Zeiss eyepiece cap with the Unimat was far greater than that needed for the BH2 adapter.

click image to enlarge (425K) Figure 17

click image to enlarge (567K) Figure 18

click image to enlarge (451K) Figure 19

click image to enlarge (257K) Figure 20

REFERENCES

(1) Delly, John Gustav (1988). Photography Through the Microscope. Eastman Kodak Company Publication P-2, Ninth Edition. Eastman Kodak Company, Rochester, New York.

NOTE

(1) “Fitting a Student Microscope with a Consumer Digital Camera” - Figure 8: Resolution Test, demonstrates that a digital camera with a Bayer color filter mosaic sensor requires about twice the number of pixels to achieve the same spatial resolution as a monochrome camera using a filter wheel or tunable liquid crystal filter for sequential capture of the image in three primary colors. Re-sampling the Bayer array image with Adobe PhotoShop using the bi-cubic method allows the number of pixels to be cut in half without significant effect on spatial resolution.