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Focus using m42 lenses on a Nikon
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PostPosted: Fri Mar 14, 2008 2:04 pm    Post subject: Focus using m42 lenses on a Nikon Reply with quote

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?


PostPosted: Fri Mar 14, 2008 2:17 pm    Post subject: Reply with quote

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


PostPosted: Fri Mar 14, 2008 7:19 pm    Post subject: Reply with quote

I dont see any consistent relationship on my nikons when I mount the M42's

patrickh


PostPosted: Fri Mar 14, 2008 7:49 pm    Post subject: Reply with quote

Thanks I'm guessing that the reasonably priced 1000mm mirror that the local camera shop has just got in would probably be useless then Wink I was hoping someone would say on very long lenses you won't get infinity but you'll get a workable range Wink


PostPosted: Fri Mar 14, 2008 8:02 pm    Post subject: Reply with quote

I used 500mm M42 mirror lens in zoo with Nikon body it made very nice portraits from 10-15m distance.


PostPosted: Fri Mar 14, 2008 8:07 pm    Post subject: Reply with quote

I have two 500mm mirrors, 300mm and 400mm regular lenses also, and all of them focus past infinity. This can be annoying. OK, they are all cheap lenses, but thats what we're talking abount.

Your best option would be to test that lens, I would say the odds are good that it will get to infinity on your Nikon as-is.

Your reasonably priced 1000mm also probably has a T-mount, customary on third party lenses of this kind, which either just screws off or can be removed reasonably easily. This is easibly interchangable from M42 to Nikon.


PostPosted: Fri Mar 14, 2008 9:38 pm    Post subject: Reply with quote

luisalegria wrote:
I have two 500mm mirrors, 300mm and 400mm regular lenses also, and all of them focus past infinity. This can be annoying. OK, they are all cheap lenses, but thats what we're talking abount.

Your best option would be to test that lens, I would say the odds are good that it will get to infinity on your Nikon as-is.

Your reasonably priced 1000mm also probably has a T-mount, customary on third party lenses of this kind, which either just screws off or can be removed reasonably easily. This is easibly interchangable from M42 to Nikon.
Sadly it's a fixed M42. I guess the thing to do is take the camera and adaptor into the shop and see. To be any use I'd need 30-40m


PostPosted: Fri Mar 14, 2008 9:53 pm    Post subject: Reply with quote

You might be lucky since esp. the very long teles sometimes have a built in "focus reserve" which allows to focus "behind" infinity. This was made to compensate for temperature changes. I would try it out, but you would need a target at least 200x the focal length away


PostPosted: Fri Mar 14, 2008 11:25 pm    Post subject: Reply with quote

kds315* wrote:
you would need a target at least 200x the focal length away


Could you explain that equation a little more? Is it saying that the distance which is indistinguishable from infinity is closer on wide lenses and further away on teles?


PostPosted: Sat Mar 15, 2008 9:19 am    Post subject: Reply with quote

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


We had this discussion already, Attila, remember?
I would love to see some comparing shots in order to understand your experience.
Does that have to do with the flange distance?
I can't explain to myself why you get this effect...


Last edited by LucisPictor on Sat Mar 15, 2008 10:05 pm; edited 1 time in total


PostPosted: Sat Mar 15, 2008 12:32 pm    Post subject: Reply with quote

ChrisLilley wrote:
kds315* wrote:
you would need a target at least 200x the focal length away


Could you explain that equation a little more? Is it saying that the distance which is indistinguishable from infinity is closer on wide lenses and further away on teles?


Chris,

This is the rule of thumb I was told once and for me has ever worked quite well. Terrestrial infinity and atromers infinity are anyway a bit different...


PostPosted: Sat Mar 15, 2008 12:35 pm    Post subject: Reply with quote

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


We had this discussion already, Attila, remember?
I would love to see some comparing shots in order to understand your experience.
Does that have to do with the flange distance?
I can't explain to myself why you get this effect...


Carsten,

sounds like "Hessisch Gebabbel" to me - could you "enligthen" me pls?
[parts of my family are from Hungen btw.]


PostPosted: Sat Mar 15, 2008 9:35 pm    Post subject: Reply with quote

I don't have Nikon camera any more, Patrick has Nikon and Canon both , perhaps he able to get test shoots with same M42 lens on both camera.


PostPosted: Sat Mar 15, 2008 10:08 pm    Post subject: Reply with quote

kds315* wrote:
LucisPictor wrote:
Attila wrote:
In my practical experience a 135mm lens on Nikon body works as 85-100mm lens on Olympus body.


We had this discussion already, Attila, remember?
I would love to see some comparing shots in order to understand your experience.
Does that have to do with the flange distance?
I can't explain to myself why you get this effect...


Carsten,

sounds like "Hessisch Gebabbel" to me - could you "enligthen" me pls?
[parts of my family are from Hungen btw.]


I just do not understand why Attila's 135mm lens works as a 85-100 mm lens at his Olympus.
Normally, an Olympus DSLR has a 2x crop, so a 135mm lens should work as a "270" mm lens.
The distance between the sensor and the mount is really short in Oly DSLRs, though. So my question is, can this influence the "effective" focal length?

The only way to find out would be to shoot the same subject with a 135mm on an Oly DSLR and with a 85mm, a 105mm, a 135mm and a 200mm lens on a (35mm) film cam and then compare the pictures.


PostPosted: Sat Mar 15, 2008 10:29 pm    Post subject: Reply with quote

2x crop is bullshit 135mm lens is never works as a 270mm lens on film.

I said a 135mm lens on Nikon body works same than a 100mm on Olympus body.


PostPosted: Sun Mar 16, 2008 12:55 am    Post subject: Reply with quote

Attila wrote:
2x crop is bullshit

Well, no, its the correct crop factor.

Attila wrote:
I said a 135mm lens on Nikon body works same than a 100mm on Olympus body.


Because a Nikon has 1.5 crop factor. 135 times 1.5 is 202.5
Olympus has 2.0 crop factor. 100 times 2 is 200.


PostPosted: Sun Mar 16, 2008 1:11 am    Post subject: Reply with quote

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.


PostPosted: Sun Mar 16, 2008 1:21 am    Post subject: Reply with quote

Magnification factor

The crop factor is sometimes referred to as "magnification factor". This usage commonly derives from the telephoto effect, in which lenses of a given focal length seem to produce greater magnification on crop-factor cameras than they do on full-frame cameras. It should be noted that the lens casts the same image no matter what camera it is attached to, and therefore produces the same magnification on all cameras. It is only because the image sensor is smaller in many DSLRs that a narrower FOV is achieved. The end result is that while the lens produces the same magnification it always did, the image produced on small-sensor DSLRs will be enlarged more to produce output (print or screen) that matches the output of a longer focal length lens on a full-frame camera. That is, the magnification as usually defined, from subject to focal plane, is unchanged, but the system magnification from subject to print is increased.

Source : http://en.wikipedia.org/wiki/Crop_factor

If you have a target from you far as 30m for example. With a 300mm lens you can't get closer with a 2x crop camera than with film camera just you will have smaller area from targeted subject. This means a 300 mm lens on a 2x crop camera will not equal a 600mm lens.


PostPosted: Sun Mar 16, 2008 1:25 am    Post subject: Reply with quote

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.

The register distance is not going to affect crop factor; that is solely a function of the sensor size. If the register distance is a lot different to the intended one then focus range will be affected, certainly, and the size of the image circle may also be affected. But if the image circle gets larger, it has no visible effect; and if it gets smaller, you will bet vignetting but it won't change the effective fov.


PostPosted: Sun Mar 16, 2008 1:39 am    Post subject: Reply with quote

Sorry about for bullshit!


PostPosted: Sun Mar 16, 2008 3:19 am    Post subject: Reply with quote

You can work out your maximum focus distance mathematically.

You start with 2 numbers: the lens focal length, and the number of millimeters difference between your M42 flange's register distance and the proper register of an M42 body. I'll call this last number the "extension".

First, convert your lens focal length into diopters by dividing 1 meter by the focal length: a 500mm lens, for example, is 2.0 diopters.

Now add the extension to the lens focal length, and convert the result to diopters: if your flange is 5mm too far from the film, then the focal length plus the extension is 505mm, which is 1.98 diopters.

Subtracting one power from the other, 2.00 - 1.98 = 0.02 diopters. Now, divide this into 1 meter, and you have 50 meters. This would be the distance limit of this lens at its infinity setting.

Using the same exercise with a 50mm lens, you have 20 - 18 = 2 diopters, for a maximum focus distance of 0.5 meters.

The 5mm figure for the extension is a purely arbitrary guess, I have no idea what the actual error will be - but if you measure that and substitute the correct value for the 5mm in the above exercise, you can predict the maximum focus distance with any focal length of lens.


PostPosted: Sun Mar 16, 2008 3:25 am    Post subject: Reply with quote

Thanks for the clear explanation, rick!


PostPosted: Sun Mar 16, 2008 2:15 pm    Post subject: Reply with quote

Thanks Rick - that's exactly what I needed


PostPosted: Sun Mar 16, 2008 2:39 pm    Post subject: Reply with quote

You're welcome!

: ) =


PostPosted: Sun Mar 16, 2008 7:24 pm    Post subject: Reply with quote

OK lets see if I understand and can apply this ...

My Cosina Voigtländer 40mm f/2 has a diopter of 1000/40 = 25.
It comes with a close-up lens as standard; this lens changes the focus range to 0.38 (max) to 0.25m (min).

1/.38 is 2.6315

Which makes the close-up lens 22.3684 diopters? (25 - 2.6315) ?

I'm not sure I have that right....