Firstly, do NOT use the BR-2 which is not compatible with auto focusing camera bodies (it doesn't clear the CPU contacts in the camera body).
Nikon no longer sells its macro reverse adptor rings although they are available on 2nd hand sites and available new through 3rd party vendors - this will allow you to use your existing legacy manual focus 20mm - 50mm lenses in reverse: essentially anythign wtih full manual aperture control (aperture ring) and a 52mm filter thread will be usuable, including AI/AI-S/pre-AI and non Nikkor lenses. The wider the lens, the higher the magnification ratio but at the cost of light loss (a higher exposure factor). Whilst you can also mount your autofocus lenes, the lack of a aperture ring means that the (typical for F-mount and other) lenses will be stopped down - you will have to be inventive to manually adjust the aperture to the desired setting or to force the aperture open via the actuation lever.
The cost of the reverse adaptor rings is very econmical (used prices for BR-2A is sometimes as low as 5 GBP) and gives every a low barrier to entry and can also give much higher magnification compared to your existing lenses, including your dedicated micro-Nikkor lenses, such as the 55mm f/3.5 AI or the 105mm f/4 AI, that may only give 1/2 magnification without additional extension tubes.
The ring itself has 3x mounting positions (unlike a normal F-mount lens that has one) - this allows you to choose the mount which is closest to the normal aperture ring position since we are using the filter thread to attach.
The Nikon materials give the following instructions:
you must focus by moving the camera and lens back and forth until the point of sharpest focus is obtainedalong with reproduction ratio of lenses (set at infinity) and augmented with exposure factor:
| Lens | Reproduction Ratio (at infinity) | Exposure Factor Impact (in stops) |
|---|---|---|
| Nikkor 20mm f/2.8 | 3.4x | 4.3 stops |
| Nikkor 28mm f/2.8 | 2.2x | 3.2 stops |
| Nikkor 35mm f/2 | 1.6x | 2.5 stops |
| Nikkor 35mm f/2.8 | 1.5x | 2.5 stops |
| Nikkor 50mm f/1.4 | 1:1.1x | 2 stops |
| Nikkor 50mm f/1.8 (Long Nose) | 1:1.2x | 1.9 stops |
| Nikkor 50mm f/1.8 (Pancake) | 1:1.19x | 1.7 stops |
Note that different max aperture results in slightly different max reproduction ratios.
Futhermore, note at 1:2 reproduction ratio (MFD) the 55mm f/3.5 AI requires 1.2 stops and the 105mm f/4 AI requires 1.6 stops exposure increase which is lens than the advertised values for all of the reversed lenses.
How does it compare
The easiest comparison to make is with a reversed 50mm f/1.8 lens (a lens that most people have to some degree) against a dedicated 55mm macro - and the results are surprisingly good.These are taken at a slight angle to allow us to show the magnification and focus.
The centre crops help us see that whilst the dedicated macro looks better I think they're close enough. Focus is not exactly the same but because of the angle of the capture, we can observed other areas of similar focus. In this limited side by side, the dedicated lens is better with contrast and sharpness but it also cost more than 5 GBP. Its clear that to explore macro photography, a reversing ring is quite a good start.
How good does it get?
Of course, the other big thing for the reversing ring is that it can get us higher magnification. Again, its surprisingly good - I don't have the extension tubes to compare how a dedicated micro lens would fare but results below are good. The following are uncropped DX images show of the same subject with the various lenses reversed - the single clock face measures about 3mm across. As we get wider, hand held focus becomes progressively more difficult. Remember that we focus by moving the camera and lens so for accurate and consistent focusing, we'd need rails.
With the 20mm reversed, this gets us to 3.x times magnification.
The 20mm f/3.5 AI seems sharper so lets explore another area.
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