Search found 18626 matches

by rjlittlefield
Tue Nov 30, 2021 11:45 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Sharpness of microscopic photos at 10x?
Replies: 15
Views: 411

Re: Sharpness of microscopic photos at 10x?

With the lens focus method can you do movements of a few microns that you can do with the Stackshot that are so useful in microscopy? How precise is it? Yes, this works fine, assuming that the lens uses internal focus so that the objective does not move as focus changes. A good way of thinking abou...
by rjlittlefield
Sun Nov 28, 2021 8:15 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Sharpness of microscopic photos at 10x?
Replies: 15
Views: 411

Re: Sharpness of microscopic photos at 10x?

With respect, this is simply not true. Then it would be appropriate to retract or revise the posts you've made indicating a one stop difference between extension and coupled lenses over the past years. FAQ entries also merit updating. Since MN and (M + 1)N has been in place for some time and is in ...
by rjlittlefield
Sun Nov 28, 2021 8:07 pm
Forum: Frequently Asked Questions (FAQs)
Topic: FAQ: How can I calculate effective aperture?
Replies: 0
Views: 58

FAQ: How can I calculate effective aperture?

There are four commonly used formulas for calculating effective aperture. Single lens, focused by extension: (1) Feff = Fnominal * (magnification+1) Coupled lenses, stopped in the front, with the rear lens focused at infinity: (2) Feff = Fnominal * magnification Coupled lenses, stopped in the rear: ...
by rjlittlefield
Sun Nov 28, 2021 10:14 am
Forum: Macro and Micro Technique and Technical Discussions
Topic: Sharpness of microscopic photos at 10x?
Replies: 15
Views: 411

Re: Sharpness of microscopic photos at 10x?

In this case a coupled lens with an infinity objective is a stop faster than a DIN objective with the same numerical aperture, meaning you need a stop less lighting and get a stop less diffraction. It's why compound microscopes changed to infinity optical trains in the 1930s. With respect, this is ...
by rjlittlefield
Sat Nov 27, 2021 2:56 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Sharpness of microscopic photos at 10x?
Replies: 15
Views: 411

Re: Sharpness of microscopic photos at 10x?

Would you mind explaining what the pros and cons are of using a lens versus extension tubes for having microscope objectives on cameras? Just curious. There are two types of objectives. "Finite" objectives are designed to be used on empty extension. "Infinity" objectives are designed to be used wit...
by rjlittlefield
Sat Nov 27, 2021 12:43 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Sharpness of microscopic photos at 10x?
Replies: 15
Views: 411

Re: Sharpness of microscopic photos at 10x?

Explaining further about the sensor resolution issue... Nikon has a rule for matching the resolutions of sensor and optics. Boiled down, that rule says to use a sensor that puts two pixels per line pair at the diffraction limit of the objective. The justification for this rule is that you need at le...
by rjlittlefield
Thu Nov 25, 2021 4:17 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Repro Nikkor and FR Nikkor max apertures
Replies: 3
Views: 110

Re: Repro Nikkor and FR Nikkor max apertures

Complementing wpl's explanation... The lens is designed for use at 1:1, where its working F-number will be effective f/2. The outermost lens elements are sized and positioned so that they can handle these f/2 cones, but because those elements are relatively close to the object and image, they can ha...
by rjlittlefield
Thu Nov 25, 2021 2:09 pm
Forum: Beginners Macro
Topic: LOMO 8/0.2 - two poppy seeds
Replies: 2
Views: 141

Re: LOMO 8/0.2 - two poppy seeds

Jon, welcome aboard! :D It is holiday today in the U.S., so I will be more brief than usual. Regarding Helicon Focus versus Zerene Stacker, some of the issues that you ask about were recently addressed at https://www.photomacrography.net/forum/viewtopic.php?p=277319#p277319 . Not mentioned there is ...
by rjlittlefield
Wed Nov 24, 2021 10:27 am
Forum: Equipment Discussions
Topic: Dual Shaft 0.9deg NEMA11/14 Steppers?
Replies: 5
Views: 219

Re: Dual Shaft 0.9deg NEMA11/14 Steppers?

How did you locate those? I've searched and searched. Google search on nema14 "dual shaft" "0.9" , with the quotes. For me the buildyourcnc.com hit turned up as #10 on the first page. The buildyourcnc.com page also turned up on first page using search at duckduckgo.com . All credit goes to beginner...
by rjlittlefield
Wed Nov 24, 2021 9:19 am
Forum: Equipment Discussions
Topic: Dual Shaft 0.9deg NEMA11/14 Steppers?
Replies: 5
Views: 219

Re: Dual Shaft 0.9deg NEMA11/14 Steppers?

https://buildyourcnc.com/item/electronicsAndMotors-nema14-17ozin-NEWBIEHACK-motors-stepping_motor-17_ozin ? https://gemsmotor.com/nema-14-stepper-motor says "GEMS Motor offer two product lines of NEMA 14 size (35mm square) stepper motors, 35HSM28 with 0.9 degree step angles (400 steps per revolution...
by rjlittlefield
Tue Nov 23, 2021 8:03 pm
Forum: Nature Photography -- Macro and Close-up
Topic: Reflector bowl test shots
Replies: 9
Views: 734

Re: Reflector bowl test shots

razorbacksrule wrote:
Tue Nov 23, 2021 7:22 pm
You have a pic of your setup? Your lighting is fantastic !
rasorbacksrule, welcome aboard!

There are lots of pictures, and extensive discussion, in the technical thread that was spun off this one. Follow the link, to viewtopic.php?f=8&t=43728 .

--Rik
by rjlittlefield
Tue Nov 23, 2021 7:54 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Front Aperture
Replies: 14
Views: 319

Re: Front Aperture

Interesting. Then I'm guessing the entrance pupil is so far back that on FF you simply cannot hide its edge from the corners of the frame. Some careful measurements could clear that up, but it's probably not worth the trouble since the issue is not related to what you're trying to accomplish.

--Rik
by rjlittlefield
Tue Nov 23, 2021 6:00 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Front Aperture
Replies: 14
Views: 319

Re: Front Aperture

When the iris was 'close' to the lens, the aperture could be made very small (~1mm) before visible corner vignetting. Clearly the 1mm iris was acting as the limiting aperture as there is visible blurring of the subject. When the external aperture is so small and so close to the lens that no part of...
by rjlittlefield
Tue Nov 23, 2021 4:53 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Front Aperture
Replies: 14
Views: 319

Re: Front Aperture

if you have a DSRL, shine a flashlight in the viewfinder. the lens will project a cone of light that is the limit for vignetting. can look at it with a piece of paper I agree, this works well and should be a sensitive indicator. I use this technique for aiming and rough focusing, as a brighter equi...
by rjlittlefield
Tue Nov 23, 2021 12:24 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Front Aperture
Replies: 14
Views: 319

Re: Front Aperture

you want to make the front aperture be the only limiting aperture in the system? In this case, you need to keep the lens entrance pupil totally outside the volume of rays defined by the image frame at the subject and the added aperture. On further thought, I realize that this "volume of rays" canno...