Reversing 50mm?

RazorSharpWO wrote:

BBbuilder467 wrote:

The same 50mm lens that reaches 1:1 with 50mm extension tubes, requires 25mm extension tubes to reach 1:1 reversed. Plus, it's attached to a 25mm adapter.

Simply reversed to the adapter, it's only 1:2.

Interesting.

Not sure what is all involved between the optics of different brands.

I know that I've personally measured the image-dimensions taken by my 50/1.2 AI-S, with a mm ruler, and the magnification is exactly 1.1x. There is also this worksheet from Nikon directly, concerning the magnification of reversing their lenses on their reverse-ringmounts:

Nikon's Own Lens Specs on their own reverse rings.

I don't think anyone's older glass is used more frequently than Nikon's, because they can usually be adapted to any brand, reversed. The lenses highlighted in green are MF lenses. I highlight those, because you can use a manual aperture, whereas the AF lenses require auto-aperture, which is sub optimal.

Anyway, if you'll note, their 50/1.2 AI-S (which I had) achieves 1.1x magnification. However, their 50/1.8 AI-S is only 0.5x.

Perhaps there's something to do with the aperture or the specs of your brand?? What was your aperture?

Here is a stack I did on a male Green Lynx spider, years ago, stacked with the 50/1.2 AI-S @ 1.1x:

Green Lynx ♂ Stacked @ 1.1x w/ Nikkor 50/1.2 AI-S, reversed.

Here is a female Green Lynx spider, stacked with the 28/2.8 AI-S @ 2.6x:

Green Lynx ♀ Stacked @ 2.6x w/ Nikkor 28/2.8 AI-S, reversed.

The quality of these older Nikkor optics is pretty darn good, and they're very small and very light, and again they can be reversed on almost any camera brand.

Not sure about the specs of what you're using, since it's a different brand, but I'm absolutely certain about the specs of what I'm using.

A few things:

1. Extending the reverse mounted lens to the correct register distance isn't necessary, at least not in most cases. Registration distance is necessary to provide infinity focus. Since macro doesn't require infinity focus, you don't need a proper registration distance to focus and take a photo. However, you will get less magnification than you otherwise would for a given focal length.

2. If you were using a lens with a symmetrical optical formula, reversing the lens would yield the same magnification as mounting it in a regular way. However, most lenses for non-view cameras are not symmetrical. Therefore, whenever you reverse mount a lens, you get somthing called lens reversal extension and that affects your magnification. The reversal extension is dependent on the optical formula of the lens, so it will be different for every lens. You have to account for that with cameras that have no through the lens metering systems, however, since all digital cameras have a built in meter, the reverse extenstion factor is irrelevant.