Macro lens vs Reverse lens

[Helen B]

Not sure what you're saying Helen.

1- What exactly do you mean by perform better? Also, Why not buy a dedicated macro lens capable of higher magnification if this is the type of shots you want? The working distance with a dedicated macro lens is much greater.

2- But how do you get 1x without a macro lens or reversal?

Remember that I am referring to lens reversal in the case of magnifications greater than 1x.

Any lens is optimised for a certain range of magnifications - in the case of lenses with moving (floating) elements the range can be quite large. Nikon call this CRC (close range correction) and Zeiss call it FLE (floating lens elements). The lens' focal length may also change when focusing. Nikon use it to achieve the ability to focus from infinity to 1:1.

When you reverse a lens, you invert the magnification it is optimised for. Something that is optimised for 1/10 when mounted normally becomes optimised for 10x when reversed.

The old 105 mm f/2.8 Micro-Nikkor had CRC, but kept the focal length fairly constant, so it would have required a throw of 105 mm to get from infinity to 1:1. It couldn't do that without an extension tube. Once you put an extension tube on a lens with CRC, the CRC gets all out of whack - the floating elements may not be in the optimum position for the magnification. (Some Zeiss lenses have separate focusing and FLE settings to get round this, by the way.)

The current 60 mm and 105 mm Micro-Nikkors reduce the throw necessary to get from infinity to 1:1 by shortening the focal length - the 105 mm is only a 60 mm at 1:1. This means that the CRC can stay in sync with the magnification, because extension tubes are not necessary.

If you want to go beyond 1:1 you will be going outside the range the lens is optimised for. One solution is to turn the lens round. That is why I suggested that even with a dedicated macro lens, reversal may be the preferable option, but it depends on a number of factors, including usability. Nikon happen to make lens reversal comparatively easy, thanks to their huge range of gizmos, and the availability of even the most obscure whotsits on eBay. As I mentioned above, one of the advantages of reversing a wide angle prime made for an SLR is that it is likely to be retrofocus. A reversed retrofocus lens becomes a telephoto (in the optical design sense of the word) that is optimised for greater than 1x magnification - the fact that it is now a telephoto increases the working distance in comparison to a non-telephoto of the same focal length.

I generally use Micro-Nikkors for up to 1:1, Apo-Rodagon-D and D2 lenses at around 1:1, reversed Apo-Rodagon-N lenses for 2x to around 6x or 8x, then either Zeiss Luminars* or reversed cine lenses over about 6x or 8x. I also use Zeiss S-Planar, Schneider Apo-Ronar, reversed Zeiss Planar or Nikkor-AM for medium and large format in the macro range. Of all these, the reversed cine lens setup is the lowest cost, closely followed by the Apo-Rodagons (at least at today's prices). I mention all this because I don't want to give the impression that I consider reversed lenses to be best in all cases. Horses for courses. Sometimes you want the highest possible resolution, sometimes you prefer usability and speed. Many options and many factors.

In many cases for small format I use PB-4 bellows to get shift and tilt - which is useful for close-up work, but it prevents most auto operation.

I'll do some reversed-lens examples using my D40x to demonstrate the degree of field flatness you might expect from a comparatively low cost setup.

* I do not have a complete range of Luminars. They are expensive and they are only optimised for an image conjugate of 250 mm - ie 250 mm from the lens to the sensor or film. Reversed lenses can be the best option for me in this case. That's why I do not have a wide range of lenses optimised for magnifications greater than 2x when used forwards.

Best,
Helen