FoV FF

A forum to ask questions, post setups, and generally discuss anything having to do with photomacrography and photomicroscopy.

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stevocem
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Joined: Mon May 01, 2017 3:44 pm

FoV FF

Post by stevocem »

I am looking for an advice: I plan to use Mitutoyo 10x, 20x and 50x with Nikon 200mm macro lens as tube. How to calculate the field of view? Is there a risk of vignetting? Many thanks.

Chris S.
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Post by Chris S. »

Stevocem, welcome aboard! :D

To get field of view, divide width of the sensor by rated the objective's rated magnification.

So for 10x, FOV = 36mm/10=3.6mm
20x, FOV = 1.8mm
50x, FOV = 0.72mm

Caveat: These numbers are reasonably close approximations. To get exact figures, you will have to measure. Reasons for this include: The sensor of a Nikon D810 is listed as 35.9mm, rather than 36mm; individual microscope objectives can vary a little bit in magnification; individual specimens of the 200mm might also vary a little bit in focal length.

I don't think you'll get significant vignetting with those combinations, but it's been a long time since I've checked, as my preference with microscope objectives is to shoot with Nikon DX (APS-C) sensors. (This is because I prefer to use only the highest-quality portion of the image circles.) Likely, someone here has more recent experience with these combos. If not, I can double check for you.

--Chris S.

stevocem
Posts: 4
Joined: Mon May 01, 2017 3:44 pm

Post by stevocem »

Thank you very much! This is very helpful. You are right, I am sure the DX version is better for this kind of work. However, as I use my IR modified Nikon D800 for almost everything, I will give it a try. I want to try to do some UV reflected (challenging) and IR 1000 as well and my camera is ready for it. I expect some problems with the objectives, due to the fact that they are not IR corrected and UV will need eternal exposures as well... We will see. Does the macro tube lens affect the resolving power of the system? Would it be better to avoid further complicated multi element glass and go with a simple tube lens, as Raynox? Many thanks again.

Chris S.
Site Admin
Posts: 4042
Joined: Sun Apr 05, 2009 9:55 pm
Location: Ohio, USA

Post by Chris S. »

stevocem wrote:Does the macro tube lens affect the resolving power of the system? Would it be better to avoid further complicated multi element glass and go with a simple tube lens, as Raynox? Many thanks again.
That particular 200mm does a very nice job at converging infinite objectives (this is not a rare trait). If you have it already, or have other uses for it, there is no reason not to use it for this purpose.

I doubt the Raynox will outperform this Nikkor in the center. However, it might (or might not) cover the corners better, at the probable cost of increased chromatic aberration. (I have not personally tried the Raynox.) The virtues of the Raynox are price ($50, vs. $1,850 for this Nikkor) and the fact that it covers full-frame 35mm pretty well. Some test images I've seen with the Raynox have more CA than I'm comfortable with.

BTW, I don't disagree per se with using FF sensors on Mitutoyo objectives. While it's not my chosen approach (most of the time), it's a perfectly rational choice for many others, as in your case. Your big challenges will likely involve pushing your VIS objectives into IR and reflected UV. It will be interesting to learn how that works out! :D

--Chris S.

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