Search found 16 matches

by Bob S
Fri Dec 02, 2011 10:42 am
Forum: Macro and Micro Technique and Technical Discussions
Topic: Can anybody recommend me a new lens
Replies: 47
Views: 12300

You probably cannot make a large improvement on the El Nikkor 50mm f/2.8. An APO-Componon or APO-Rodaogon might have slightly less color fringing, but it might not be a big enough change to notice. You could upgrade the Edmund optics Nikon 10x Achromat by getting an APO microscope onbjective, but ag...
by Bob S
Wed Nov 09, 2011 8:52 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Need help with Lighting
Replies: 4
Views: 2214

Get an empty cardboard box and/or a large piece of black cloth. Make an enclosure around your stacking setup. Fire the flash all you want without bothering anyone.
by Bob S
Sat Oct 22, 2011 1:40 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Please help - 100x objective not working
Replies: 31
Views: 11269

If you have a condenser with NA 0.9 and no oil, then your objective lens cannot resolve better than NA 0.9. If you want to get the full resolution of your lens, you need the correct condenser for it.
by Bob S
Tue Oct 18, 2011 2:28 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Vignetting
Replies: 25
Views: 8998

Steve, there are two types of vignetting happening, and you are probably getting confused between them. It is easy to get confused when you try to use optical parts in ways that they were not designed for. The first issue is simply a limitation of the microscope objective. It was designed to have a ...
by Bob S
Mon Feb 07, 2011 9:50 am
Forum: Equipment Discussions
Topic: Micro Nikkor 55 mm as infinity objective
Replies: 9
Views: 5482

Chris, you have it exactly correct. When I wrote "focused closer than infinity" I meant "focused at a distance less than infinity", not "the lens is closer to the sensor than it would be at infinity focus". I apologize for the lack of clarity. What I was trying to convey is that if you have one of t...
by Bob S
Tue Feb 01, 2011 11:04 am
Forum: Equipment Discussions
Topic: Four at 5X: A pixel peep show!
Replies: 43
Views: 19813

If you are testing a simple achromat with non-symmetric external shape for use as a tube lens, try to test it at both orientations. Aberration performance will depend on the orientation. (Whether the effect will be large enough to be visible is not obvious.) For a simple lens used at infinity for "n...
by Bob S
Tue Feb 01, 2011 8:30 am
Forum: Equipment Discussions
Topic: Micro Nikkor 55 mm as infinity objective
Replies: 9
Views: 5482

I suspect that it will never be a good idea to focus the tube lens closer than infinity, at least not in hopes of improving image quality. If you draw a simple ray diagram you will see that if the tube lens is focused closer than infinity then the rays entering it must be diverging, but the front ob...
by Bob S
Sun Jan 09, 2011 7:16 am
Forum: Equipment Discussions
Topic: Playing with a cheap macro flash
Replies: 4
Views: 1524

Keep in mind that the wires running from the capacitor to the flash tube will be just as dangerous as the capacitor itself.
by Bob S
Sun Dec 12, 2010 5:49 pm
Forum: Equipment Discussions
Topic: Magnetic lighting stage for Bratcam
Replies: 33
Views: 53194

I had been thinking about 10X, if you are willing to try a test. The thought was as follows. At some low magnification, an arm will certainly provide enough stability and can provide precise enough position, and is certainly cheaper, more suited to field use, and less expensive than a pile of ball b...
by Bob S
Sun Dec 12, 2010 10:14 am
Forum: Equipment Discussions
Topic: Nikon CF Plan 50X 0.55 inf/- EPI ELWD, initial impressions
Replies: 19
Views: 18832

I am surprised that you did not find a decrease in image quality when you changed the focus of the telephoto lens to the near limit. Changing the focus of the rear lens away from infinity is optically equivalent to creating a tube length error in a finite objective, and should give noticeable spheri...
by Bob S
Sat Dec 11, 2010 7:41 am
Forum: Equipment Discussions
Topic: Magnetic lighting stage for Bratcam
Replies: 33
Views: 53194

Have you tried using one of the arms to hold the subject?

I wonder whether it would work or whether it would have problems with vibration or with inability to set a precise position.
by Bob S
Fri Dec 10, 2010 3:48 pm
Forum: Equipment Discussions
Topic: Infinity objective with Raynox DCR-150 as tube lens
Replies: 16
Views: 20676

Regarding blue halo removal: I have seen reports that using a simple UV-cut filter can reduce blue haloes on some lenses. The claim is that the filter removes UV and a small amount of blue light. The lens has poor corrections for these colors; this is the reason for the haloes. Removing the light re...
by Bob S
Tue Nov 30, 2010 3:57 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Diffused reflected rather than diffused transmitted light.
Replies: 24
Views: 7347

If I remember physics correctly, there are some good reasons for the results of the parabolic and flat reflectors. The parabolic reflector is designed for specular reflections, where the angle of reflection equals the angle of incidence relative to the reflecting surface. In this case a parallel bea...
by Bob S
Sun Oct 03, 2010 5:53 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Telecentric optics, third round.
Replies: 26
Views: 41729

any advantage for ordinary use?

Rik, would a telecentric system offer any advantages for non-stitched stacked images. For example, if it allowed disabling automatic scale adjustment (which I am assuming is a re-sampling operation) would it give better detail? For another guess, by eliminating the "seeing around the foreground effe...
by Bob S
Tue Aug 17, 2010 5:24 pm
Forum: Equipment Discussions
Topic: Objective Advice Needed—New Member
Replies: 37
Views: 15404

I would try cutting the step size in half.

Post another example and specify everything about it; aperture, lens, magnification, step size, flash type and settings, and everything you can think of. It might let someone see something obvious that is being overlooked.