Best Nikkor used in reversed position

[DanAa]

Which wide Nikkor will give the best result when used in reversed position using BR2? So far I have used my old Nikkor-H Auto 3.5, f=28mm. Any comments?

[Bjørn Rørslett]

This depends on the magnification desired. Your 28 is quite good, but it needs a lot of extension in order to perform at its best. The lens should not just be put on a reversing adapter straight onto the camera.

Do not forget the mismatch of the imaging areas on either side. In a reversed position, the lens has a field of view many times bigger than the actual field "seen"  by the camera. Thus, your need to block off the extraneous coverage to prevent as much as possible of non-image forming rays entering the camera to cause loss of contrast and sharpness or even a hot spot.

[DanAa]

Thanks Bjørn, and for reminding me about the subject of the 'field of view'. I guess that the K-rings can do a proper job as a shield.

[Bjørn Rørslett]

No, they are too wide plus will shade and/or interfere with the subject because the working distance is so short. Drill a medium-sized hole in a rear lens cap as an ad-hoc solution until you can invent something better.

[Roland Vink]

If you are using a BR-2 reverse adaptor, chances are you also have a BR-3 also? This attaches to the bayonet mount of a reversed lens and has a 52mm filter thread at the other end. Its purpose is so you can add filters to a reversed lens, but it also acts as a short hood/lens protection for the reversed lens. The depth is about the same a rear lens cap, but it is still rather wide like a K ring (BTW, the BR-2 and BR-3 work well with the K ring set and extend the possibilities even further). Or you can use a drilled out hole in a rear cap as Bjørn suggested. Or simply "focus" the reversed lens close - it doesn't do anything to the focus since the optics are fixed to the camera via the BR-2, but it does extend the barrel over the rear element, giving some protection.

As for which lens is best reversed, for magnifications around 4x (for example) in theory the best is a lens which is sharp at 1:4 in normal position, such as the AIS 28/2.8. Because this lens has CRC (floating elements) the focus ring will make some difference to the image quality - even though it does not focus the lens in reversed position, it does configure the lens so it is better corrected for this magnification. So in this example, with the AIS 28/2.8 in reverse position, I would focus it "close" to 0.2m, because in normal position it is focused to about 1:4. If you want magnifications around 6x, then the focus ring should be set to the position where the lens would get 1:6 in normal position, and so on.

[DanAa]

So the AiS 28/2.8 is better than the old 28/3.5 for this purpose?

[Bjørn Rørslett]

Perhaps. It has CRC, as Roland pointed out, but that is no guarantee of improved results as the optics are more complex than the older 28. I have tested various CRC-capable lenses for photomacrography and find it not obvious that theory and practice return the same results.

A point not often mentioned is the weight of the lens. You do put a strain on the filter threads and a lighter lens can provide more stability than a heavy one. Ideally one should only use the optics on their own, i.e. a lens head without the focussing helicoid.

As an alternative, you might look into lenses made for 16 mm cine film. A typical focal length is around 25 mm and these lenses are fast and lightweight compared to equivalent (D)SLR lenses. As they are designed to illuminate a much smaller image circle than what demanded by FX, the field mismatch mentioned earlier is much less of an issue with cine lenses. They still need to be reversed, of course, and working distance may be shorter than your 28 Nikkors.

[DanAa]

Thanks to both of you for informative posts and practical suggestions.