Aperture setting when using reversed lens ?

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AndrewC
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Aperture setting when using reversed lens ?

Post by AndrewC »

When using a reversed lens (say an El-Nikkor 50mm f2.8 ) reversed on a bellows, what aperture setting do you use ? I know that most lens when used conventionally have a sweet spot at about f8 to f11 but I'm not quite so sure when reversing them.

rjlittlefield
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Post by rjlittlefield »

The sweet spot depends on magnification, and it's generally at a wider aperture when the lens is reversed than when it's used normally.

I haven't tested that exact lens, but other people have reported a sweet spot around f/5.6.

See http://www.photomacrography.net/forum/v ... .php?t=424 and http://www.photomacrography.net/forum/v ... .php?t=676 for some discussion of things to think about.

--Rik

AndrewC
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Post by AndrewC »

Thanks for the answer Rik, it seems like most of the lenses work best one or two stops down from wide open. I'll run my own series of tests once my current eBay shopping spree bears fruit but it is always nice to benchmark against others.

Andrew

Cyclops
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Post by Cyclops »

The problem with reversing a modern fast lens is that one end is bigger than t'other. The lens is asymmetrical so that when reversed you end up with a smaller aperture(the rear of the lens is now the front element and its 2 lot smaller than the true front element) This isn't too bad if you have good TTL flash and its digital but on older systems it can be a nightmare,especially with wide angles,which give the highest mag. I remember doing this with a 24mm on a film camera and having to factor in the pupillary magnification factor then work out the new subject to flash distance by hand!
Canon 5D and 30D | Canon IXUS 265HS | Cosina 100mm f3.5 macro | EF 75-300 f4.5-5.6 USM III | EF 50 f1.8 II | Slik 88 tripod | Apex Practicioner monocular microscope

rjlittlefield
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Post by rjlittlefield »

Ah yes, the "good old days" of film, when one did elaborate calculations to figure out what should work best, bracket around that to cover the likelihood that the calculation was not correct or not appropriate, and wait from hours to days to discover which setting in the bracket really did work best.

Somehow I don't miss those days at all. :D

These days, I find that theory is still critical to understanding what varies with what and where the fundamental limitations lie, but experiments are so quick and easy that most questions like "what's the optimum aperture" are best answered by just trying them.

In the specific case of the EL Nikkor 50 mm f/2.8, the lens is definitely asymmetric (the rear element is very strongly curved), but the pupillary magnification factor is so close to 1 that it's not an issue.

--Rik

Cyclops
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Post by Cyclops »

Thing is if i want to do true macro I have to use the Canon which is a film camera,i so wish i could afford to upgrade to a DSLR!
Canon 5D and 30D | Canon IXUS 265HS | Cosina 100mm f3.5 macro | EF 75-300 f4.5-5.6 USM III | EF 50 f1.8 II | Slik 88 tripod | Apex Practicioner monocular microscope

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