Infinity objective and tube lens dissolute chatter

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Steve S
Posts: 70
Joined: Fri May 10, 2013 1:52 pm
Location: Southern Arizona, USA

Infinity objective and tube lens dissolute chatter

Post by Steve S »

Thread hijacking has passed from crime wave to pandemic, and we have quite enough of pandemics (or perhaps perceived pandemics) right now, thank you very much.

I started this thread to answer a speculation by Macro_Cosmos about the use of 100-400mm lenses as tube lenses. He mentioned Sigma and Sony, and I used the Sigma in Canon mount on several Sony cameras until adapter glitches sent me to the native Sony offering. Both these lenses perform very well indeed at infinity at all focal lengths. In spite of bleak pessimism I hung an M Plan Apo 10X on the Sony and took a look. Pessimism vindicated: hopeless vignetting, although at 400mm you could get away with square format. Some weeks ago in boyish enthusiasm I hung a Mitty on the Zeiss 135mm f/2.8 Batis, with similar results. Lots of excellent lenses are epic fails behind an infinity objective, but occasionally one works: I have an elderly Tamron 180mm f/3.5 allegedly auto-focus lens which has outstanding infinity performance, easily besting a couple of expensive Nikon zooms to which I compared it, and a recent stack with the M Plan Apo 20X looked quite good.

Maybe the location of the entrance pupil is a factor in vignetting.

One does sometimes weary of the vogue for infinity objectives. Consider, for example, at ~5X, a reversed Apo Lanthar, 65mm or 50mm set at an indicated f/4 and with the focusing ring set to the appropriate conjugate: either lens covers 44X33mm with ample resolution to the corners of the frame. (It makes sense if you think about it: you're only using the central part of the angular field of the lenses.) It does take a lot of extension. Another interesting lens on the GFX 100 is the JML 21mm f/3.5, which had its fifteen minutes of fame on this forum several years ago: uniform resolution across the field, although a little NA-challenged.

ohdeeremee
Posts: 36
Joined: Mon Nov 24, 2014 9:50 am
Location: Colorado

Re: Infinity objective and tube lens dissolute chatter

Post by ohdeeremee »

FWIW,
I have been using Nikon CFI Plan 4x (MRL00042) and 10x (MRL00102) on Nikon D90, D300s (APS-C) and using a Nikon 70-300 f/4.5-5.6 G lens as a tube lens for many years.

With the 4x, I start to vignette when the lens is set to 175mm or less (about 3.7x) and can take it up to about 6.1x at 300mm
With the 10x vignette starts at abut 150mm (about 8.0x) and is good to about 15x at 300mm.

I have also charted them on 70-200 f/2.8
vignette starts at 120mm (2.4x) on the CFI 4x
and starts at 120mm (6.0x) for the 10x

Of course the lens f-stop is set to wide open.

This setup works quite well for me, as it gives a variable magnification with only slight focus type issues around the extreme edges of the image (but who looks at edges...?)
Works great on bugs as they come in various sizes....

George

Steve S
Posts: 70
Joined: Fri May 10, 2013 1:52 pm
Location: Southern Arizona, USA

Re: Infinity objective and tube lens dissolute chatter

Post by Steve S »

I should have mentioned I was referring to full frame. Trying a 70-300mm is a good idea, will get around to it sometime.

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