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Focus using m42 lenses on a Nikon
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PostPosted: Sun Mar 16, 2008 9:12 pm    Post subject: Reply with quote
No, your closeup lens is 1/.38, or 2.6 diopters (a rather uncommon value). The distance that your lens focuses to when set at its infinity position is the inverse of the power of your closeup lens.

The lens alone is 25 diopters; with the closeup lens added it's it's 25+2.6, or 27.6 diopters, which is another way of saying its focal length is 36.2mm. But its mount puts it (optically) 40mm from the film, so it focuses close. The difference between 40 and 36.2, about 4mm, is the amount of extension that it would take that same lens to focus to that same distance without the diopter attachment.


PostPosted: Sun Mar 16, 2008 11:47 pm    Post subject: Reply with quote
rick_oleson wrote:
No, your closeup lens is 1/.38, or 2.6 diopters (a rather uncommon value). The distance that your lens focuses to when set at its infinity position is the inverse of the power of your closeup lens.


Ah, okay. (Is there a similar equation to say how the closest focus distance changes?)

rick_oleson wrote:
The lens alone is 25 diopters; with the closeup lens added it's it's 25+2.6, or 27.6 diopters, which is another way of saying its focal length is 36.2mm. But its mount puts it (optically) 40mm from the film, so it focuses close. The difference between 40 and 36.2, about 4mm, is the amount of extension that it would take that same lens to focus to that same distance without the diopter attachment.


What would the difference be between this lens with the close-up lens fitted, and this lens without the close-up lens and with a (hypothetical) 4mm extension tube between body and lens?


PostPosted: Mon Mar 17, 2008 1:25 am    Post subject: Reply with quote
Yes, there is .... the extension of the focus helical is just added to the "extension" value in my original note.

The 40mm lens on a 4mm extension will be very similar to that same lens with the 2.6d closeup lens added. The main difference is that the closeup lens shortens the focal length of the system by 4mm, so what you end up with is a 36mm lens on a 4mm extension. Other than the 10% difference in focal lengths you have a very similar situation in the end.


PostPosted: Mon Mar 17, 2008 3:25 pm    Post subject: Reply with quote
Well I took the M42 adaptor and D200 into the shop and sadly it's a non-starter as the prism housing means I'd have needed to use at least a 20mm extension ring Sad


PostPosted: Mon Mar 17, 2008 5:11 pm    Post subject: Reply with quote
Poop! I'd forgotten about the overhang issue. I couldn't use big mirrors on my Nikon F Photomic for the same reason......

:(=


PostPosted: Mon Mar 17, 2008 5:51 pm    Post subject: Reply with quote
ChrisLilley wrote:
Attila wrote:
You have a Nikon body try it with a lens what has no right flange distance (M42) and see how it works. Also try with a lens with right flange distance (Nikon) and see difference.


Attila, I just agreed with you! (well apart from your random bullshit remark) that 135mm on Nikon and 100mm on Olympus would have the same field of view.


Yes, but a 135mm lens on a Nikon will have another FoV (about 200mm equiv. to film) than a 135mm lens on an Oly DSLR (about 270mm equiv. to film).


Attila wrote:
In my practical experience a 135mm lens on Nikon body works as 85-100mm lens on Olympus body.


Now, I think I understand what Attila means: two different bodies, two different lenses = similar FoV. You need a 100mm lens on an Oly DSLR to get the same FoV on a Nikon DSLR.

I was pointing at: two differently "cropped" bodies, one lens = different FoV. If you use one lens on two different bodies (e.g. Oly and Nikon) you will get two different FoV. There can be no doubt about it.

Can we agree on that?


PostPosted: Mon Mar 17, 2008 6:44 pm    Post subject: Reply with quote
Yes.


PostPosted: Wed Mar 19, 2008 11:45 am    Post subject: Re: Focus using m42 lenses on a Nikon Reply with quote
Richard_D wrote:
Okay I know I can't get infinity focus on a Nikon with M42 lenses but is there a way og working out what the maximum focal distance is for a given lens? Do longer lenses give a greater long focus?


yes, longer lenses give longer focus reach.

I have Nikon D70 and m42 adapter without optics.

I have tried several m42 lens:

0. zenitar 16/2.8 fisheye -> I had to convert it, it went to ~0.5m
1. flektogon 35/2.4 - it is now gone, very good for macro, focuses to ~1m
2. super takumar 50/1.4 - focuses to ~1.5m
3. jupiter 9 (85/2) - great for portraits, focuses to ~3-4m, so it's usable as a portrait lens
4. jupiter 11A (135/4) and CZJ Sonnar 135/3.5 - focus to ~6m
5. CZJ Sonnar 180/2.8 P6->M42 adapter *before I got p6->Nikon adapter which solves the issue*, you can get ~10m focus distance
6. CZJ Sonnar 300/4 p6->M42 adapter *before I got p6->Nikon adapter which solves the issue*, you can get ~30-40m focus distance

mirror Panagor 500/8 which, as probably all mirror lens do, focuses past infinity so I can get full focus scale with it.


PostPosted: Sat Mar 22, 2008 3:39 pm    Post subject: Reply with quote
Rick, thanks for the formula!


PostPosted: Sat Mar 22, 2008 3:51 pm    Post subject: Reply with quote
Ivan , thank you for clear list , this is great help for people.
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