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Pentax lens on Nikon camera

Vincent Leleu (Digital Studios) , Nov 16, 2006; 11:03 a.m.

Hi, I use a Nikon F90 in an underwater housing and would like to be able to fit my cherrished Pentax 16mm f/2.8 fisheye lens on it. I have looked at other posts regarding fitting lenses on different manufacturers camera body.

Some of them suggest to buy the body that goes with the lens, which is not an option in my case since I have the complete underwater system that goes with the camera.

Also I have seen discussions about Tamron adaptall, M42, adaptors, flange to focal plane distance etc, but I must say that I am confused in what I should look for in order to be able to fit my Pentax 16mm on the Nikon F90x.

Could anybody help me in understanding how the adaptall, M42 and other adaptors work and which ones to look for on eBay or second-hand?

Thanks a lot.



Paul Noble , Nov 16, 2006; 01:27 p.m.

First of all, is the Pentax lens a K-mount or screw-mount lens? There are adapters to allow a Pentax screw-mount (M42) lens to be used on a Nikon camera, with limitations. As far as I know, there are no adapters to allow a Pentax k-mount (bayonet) lens to be so used.

M42 is the formal name of the so-called Pentax or Universal screwmount lenses. It refers to the fact that the thread is 42mm in diameter x 1 mm per thread.

Tamron's Adaptall II is a proprietary system used on some lenses from that manufacturer. You buy an Adaptall lens, which is the same for all cameras, and you buy an adapter that mates that lens (or any Adaptall lens) to your specific camera. If you get a new camera, you simply buy a new adapter and keep the lens. This system will not help you mount a Pentax (screw or k-mount) lens to a Nikon camera.

The problem with adapting Pentax lenses to Nikon cameras is that the Nikon body is thicker than the Pentax body, by a couple of millimeters. This means that, even with an adapter, a Pentax (screw mount) lens can not focus to infinity on a Nikon body. There are adapters that include a lens that modifies the focal length of your pentax lens, so that it will focus to infinity. I strongly suspect that the image quality suffers at least a little when using such an adapter. In this respect, such an adapter is like a teleconverter and we all know that the image suffers in that case.

Paul Noble

Jochen Schrey , Nov 16, 2006; 01:39 p.m.

Just forget it; no chance at all. At least you couldn't ever focus to infinity, if you don't sacrifice either the Nikon's and the lens' mount and any comunication about and operating of the aperture by the camera and this job wouldn't be cheap.

Franklin Polk , Nov 16, 2006; 06:09 p.m.

The flange distances are the same for both K mount and M42 mount, so that doesn't really factor in. Either way, an adapter is impossible for Nikon (flange distances: Nikon:46.50mm Pentax: 45.46) if you want infinity focusing. I'm sure someone like S.K. Grimes could convert the lens to F mount (nikon), but it would probably cost around $400, and the lens would no longer be useable on a Pentax camera.

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