20x Objective recommedation

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phil_H
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Joined: Sun Sep 13, 2015 11:50 am
Location: Grimsby

20x Objective recommedation

Post by phil_H »

I am interested in purchasing a 20x objective. Does anyone have any recommendations, please? I'm using a Canon 6D with tube and Raynox lens or can use a 200mm lens. Many thanks.

santiago
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Post by santiago »

Hi phil_H,

I'm not an experienced user of microscope objectives, but I own a Mitutoyo 20x/0.42 and I'm quite satisfied with its performance. The lens has great chromatic aberration correction, good resolution and a convenient working distance of 20 mm. Mitutoyos have good reputation in general.

There are other brands (i.e. Nikon, Olympus) of lenses which are also good but I don't have experience with those in 20x magnification.
Santiago
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ChrisR
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Post by ChrisR »

At 20x there are few choices. Fewer would reasonably fill 24x36, too. :(
Chris R

bs0604
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Post by bs0604 »

"Fewer would reasonably fill 24x36, too". To what does this refer?

ChrisR
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Post by ChrisR »

Microscope objectives are designed to give a useful image diameter (Field Number) of maybe 20mm diameter or 26.5mm. That's pushing it for APS, too small for your sensor. You can sometimes "get away with" using the image outside the specified FN (depending how fussy you are). The Mitutoyo is good - there's degradation but it's quite usable. For 24 x 36 you need 43mm diameter.

Others aren't as good.
They're expensive though, and they're quite fragile so buying used is risky.

You will also need Long Working Distance, and correction for use without a coverslip.
Chris R

rjlittlefield
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Post by rjlittlefield »

bs0604 wrote:"Fewer would reasonably fill 24x36, too". To what does this refer?
The Mitutoyo M Plan Apo 20X NA 0.42 will comfortably fill a fullframe sensor (24x36 mm) at rated magnification, with good quality clear into the corners. Mine even tests well at 10X on APS-C, using a 100 mm rear lens. That means the objective covers an area on subject at least 2.7 mm wide, 54mm image circle at 20X.

I am not aware of any other 20X objective that I would trust to fill a fullframe sensor with good image quality. Even APS is pretty challenging.

--Rik

phil_H
Posts: 24
Joined: Sun Sep 13, 2015 11:50 am
Location: Grimsby

Post by phil_H »

Hi all

Thank you for your advice, I think I will stick with my Nikon 10x for the time being. As a matter of interest I have just got a Canon 40d which is a crop sensor camera to try.

Many thanks again

Phil_H

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