M42 lenses on a Nikon F body.... with infinity focus

480sparky · Aug 2, 2015

OK, I already know that a glassless adapter for sticking an M42 lens on a Nikon F-mount body will lose infinity focus, but my question is: How far from infinity can one focus? 100 feet? 50 feet? 20 feet? 10 feet? I'm sure this will vary with different lenses, but is there a general rule of thumb?

Just asking before I drop 3400 dimes on an M42 lens.

Fixcinater · Aug 2, 2015

The longer the focal length, the further you can focus. Wide angles are not so usable thusly.

Chan Tran · Aug 2, 2015

Fixcinater said:
The longer the focal length, the further you can focus. Wide angles are not so usable thusly.

Nikon lenses are plenty and inexpensive enough and good enough to put on the Nikon F. Not too much reason to try mounting lenses of different mount on a Nikon.

Fixcinater · Aug 2, 2015

Chan, I agree but maybe OP is looking for something rare and found a good deal on a Pentax piece. I'd still look for the correct body to mount it on but for longer lenses, it is not totally out of the question.

480sparky · Aug 2, 2015

Chan Tran said:
Nikon lenses are plenty and inexpensive enough and good enough to put on the Nikon F. Not too much reason to try mounting lenses of different mount on a Nikon.

How many old, cheap Nikkor have double-digit aperture blade counts?

analoguey · Aug 3, 2015

480sparky said:
How many old, cheap Nikkor have double-digit aperture blade counts?

Do (all/most) the M42 lenses have that? This should mean smoother bokeh? Or smoother tonality?

480sparky · Aug 3, 2015

analoguey said:
Do (all/most) the M42 lenses have that? This should mean smoother bokeh? Or smoother tonality?

No. Most are 8 or less.

Fixcinater · Aug 3, 2015

The early preset versions will almost exclusively have more blades but once they went to auto aperture setups, friction reduced the number available to use so the Super Takumars and later lenses from Pentax will have 6, 7, 8 blades.

It doesn't automatically mean smoother out of focus regions AKA better/smoother bokeh. It just means you won't see hexagonal out of focus highlights/speculars. The rest of the optical system determines the rest of the quality of the out of focus regions.

You can compare the bokeh of the early Helios 44-2 (Biotar 58mm f/2.0 clone) with many aperture blades, either 11 or 13 against the bokeh of the later Helios 44M series (44-7 amongst others) with less blades. Flickr is a good resource for such a comparison as you likely know.

jochen · Aug 3, 2015

Hello,
I have several M 42 Pentax lenses and several Spotmatics. When they introduced the multicoated lenses "Super Multi Coated Takumars", the number of blades in some but not all lenses was increased from 6 to 8. The 1,4/50 Super Takumar had 6, the SMC version 8. the latest SMC 1,8/85 has 8, the ST 1,9/85 has 6. The 1,8/55 has always 6. The best way to use the superb SMC Takumars is to buy a cheap and reliable M 42 body for them, e.g. a Spotmatic. Than you can use the automatic diaphragm too.

Chan Tran · Aug 3, 2015

480sparky said:
How many old, cheap Nikkor have double-digit aperture blade counts?

In that case I would use a camera like my S3. No need for a Nikon F. Easier and less expensive than an adapter. I doubt that a Nikon body would make a different in quality.

analoguey · Aug 3, 2015

480sparky said:
No. Most are 8 or less.

Not sure I understand this versus the previous comment,below . I thought the one below indicated most m42 lenses would 10+ bladed!

480sparky said:
How many old, cheap Nikkor have double-digit aperture blade counts?

480sparky · Aug 3, 2015

analoguey said:
Not sure I understand this versus the previous comment,below . I thought the one below indicated most m42 lenses would 10+ bladed!

It's pretty simple.

How many cheap Nikkors have double-digit aperture blade counts?

Note the question does not refer to any M42 lenses.

Russ - SVP · Aug 4, 2015

Chan Tran said:
Nikon lenses are plenty and inexpensive enough and good enough to put on the Nikon F. Not too much reason to try mounting lenses of different mount on a Nikon.

I agree. Why go through all the trouble, when the cheaper Nikon lines are better than the M42 glass that you want to use???

zanxion72 · Aug 4, 2015

Just too many aperture blades do not make up a great lens. I have seen Jupiters and Pentacons with a mesmerizing lot of many aperture blades, but with poor optical performance and being a pain to focus even on static subjects. Many of them where so soft wide open that it was taking so long to focus correctly that the subject got bored, started complaining, or just left.
It is meaningless trying to get them on Nikons, while one can buy some M42 body for the cost of an adapter that would do just well with these lenses.

analoguey · Aug 4, 2015

480sparky said:
It's pretty simple.

How many cheap Nikkors have double-digit aperture blade counts?

Note the question does not refer to any M42 lenses.

Unless you were starting an entirely new thread within your own thread it was in comparison to m42 on Nikon bodies.
You can spin it anyway you want to, not going to change that.

480sparky · Aug 4, 2015

Kiron Kid said:
I agree. Why go through all the trouble, when the cheaper Nikon lines are better than the M42 glass that you want to use???

analoguey said:
Unless you were starting an entirely new thread within your own thread it was in comparison to m42 on Nikon bodies.
You can spin it anyway you want to, not going to change that.

I'm looking at a Pentacon 135mm lens. It's an M42 mount. It has 15 aperture blades.

Now, would you care to tell me which Nikon 135mm lens I can buy has 15 aperture blades?

zanxion72 said:
........It is meaningless trying to get them on Nikons, while one can buy some M42 body for the cost of an adapter that would do just well with these lenses.

Because I want to put it on a Nikon. I don't want to buy yet another body just for a certain lens.

miha · Aug 4, 2015

Why is the number of blades important? Just asking. The out-of-focus quality of this particular Pentacon is nothing special, but this is all subjective, of course: http://vintage-camera-lenses.com/wp-content/uploads/2014/01/Pentacon_135_MC_2.png

480sparky · Aug 4, 2015

miha said:
Why is the number of blades important? Just asking. The out-of-focus quality of this particular Pentacon is nothing special, but this is all subjective, of course: http://vintage-camera-lenses.com/wp-content/uploads/2014/01/Pentacon_135_MC_2.png

Not knowing which version it was taken with, I can't speak for it.

frank · Aug 4, 2015

Back to the original question:

Relying solely on my (hazy) memory, when I used a glass-less adaptor to mount a 50f1.4 screw mount Super Takumar on a Nikon F mount body, I could focus out to about 6-8 feet.

zanxion72 · Aug 5, 2015

480sparky said:
I'm looking at a Pentacon 135mm lens. It's an M42 mount. It has 15 aperture blades.

Now, would you care to tell me which Nikon 135mm lens I can buy has 15 aperture blades?

Because I want to put it on a Nikon. I don't want to buy yet another body just for a certain lens.

The Nikon 135mm f/2.8 AI/AI-S has just 7 aperture blades, produces an equally creamy bokeh (if not better than that Pentacon delivers) and it is a hell lot sharper than the Pentacon. Also, it focuses a lot easier with a focusing ring of a shorter throw.

If you care so much for the number of aperture blades, get a Tair-11 that has 20.

Plus as Frank has stated, you will need an adapter with correction glass to get it to focus far. It will degrade its IQ quality a lot.

480sparky · Aug 5, 2015

zanxion72 said:
..........Plus as Frank has stated, you will need an adapter with correction glass to get it to focus far. ........

Which I stated I knew quite clearly in my OP.

My question again is: Without an optical element in the adapter, what could I expect for a maximum focus distance mounting an M42 lens on a Nikon F-mount body?

That is my question. It's not about whether a particular lens is sharp or crap. It's not about the quality of a particular lens' bokeh. It's not about an off-brand v. a Nikkor. It's not about buying another body just to use said off-brand lens.

frank · Aug 5, 2015

And you got an answer from my poor memory. I remember clearly that I was disappointed by the short range. I don't know what the difference in max focusing distance would be between the 50 Takumar lens that I tried and the 135mm lens that you have.

michr · Aug 5, 2015

Anyone know how to figure this out mathematically? The lens makers formula is pretty straightforward when talking about normal lenses. Is there a similar formula for telephoto lenses?

m42 -- 45.46 mm

Nikon -- 46.50 mm

thickness of the adapter -- ? mm

Let's assume the adapter adds 2mm to the flange focal distance, 3mm total, for a distance of 48.5mm.

so the simple ratio

focal distance + lens distance = lens focal length

1/6210 + 1/138 = 1/135, so 6.2 meters.

But I don't have any idea if those numbers apply to a telephoto lens.

I assume that you already have at least one lens. Maybe focus the lens at infinity, take the lens off and position it 3mm from the from of the camera mount to give you an idea of the difference. Twisting the focus ring and measuring the change in distance of the front element might give you the same information. All the better if the lens is close to 135mm focal length.

It really all depends on the thickness of the adapter. If you can get a recessed adapter or something where the total difference is only 2mm then you can end up with something like this

1/9247 + 1/137 = 1/135 = 9.25 meters

according to these made up numbers, with an infinitesimally thin adapter, the 1mm difference in flange/focal between the m42 mount and the Nikon mount still only lets you focus out to about 60 feet.

1/18360 + 1/136 = 1/135 = 18.36 meters

These figures should give you a ballpark idea. If I'm completely off-base with these numbers, someone will surely correct me.

Nodda Duma · Aug 5, 2015

michr said:
Anyone know how to figure this out mathematically?

Yes although it's not the lens maker formula you are using. Use the Gaussian equation for a thin lens which maps the object distance, z, to image distance, z'.

1/z' = 1/z + 1/f

That'll get you close. Note sign conventions states z is a negative value. Rays always trace from left to right, and distances to left (into object space) are negative while distances to right (image space) are positive. It's very biased against left handed people like me.

So knowing that z' = f for z = -infinity, solve for z when z' = f - 2mm or whatever the delta is. That will give you maximum distance you can bring to focus (assuming your lens has a hard stop at infinity).

So for 135 mm lens, 1 / (1/137 - 1/135) = -9257 mm is farthest you can focus, or objects 9.257 meters away.

For 50, it's about 1.3 meters.

There's a calculator on this page:

http://www.mystd.de/album/calculator/

Which will do this math if you enter the focal length and the difference in flange length (e.g. 2mm) as the extension tube value.

Btw I recommend a Field Guide to Geometric Optics by John Grievenkamp...my copy is from when I took his geometric optics course. Handy for looking up fundamental optical calculations.

f/16 · Aug 5, 2015

Just to give you an idea of reproduction ratios, I tried the Takumar 28 and 50mm M42 lenses on my Nikon F2 with the Nikon-M42 adapter(no optics in the adapter). With the 28 focused to infinity and the camera to subject distance adjusted to focus, I could see 19 inches across the frame left to right looking at a tape measure. With the 50, I could see 37 inches. I did not have enough room in this room to test the Sears 135mm. So the 28 is only good for close up stuff and you could probably do head and shoulder portraits with the 50. And I assume you would be able to do full body portraits with a 135. According to my calculations, the adapter puts the lens about 2.2mm too far forward for infinity focus.

M42 lenses on a Nikon F body.... with infinity focus

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