M42 Lenses on current DSLRs / Focus

[freiform]

Hi, 

I want to get a fast lens with fixed focal length for widefield imaging, preferably with a proper focus ring. I plan on using it on a modded Canon 1000D and maybe on my Nikon D3100. As there are many 2nd hand, high quality lenses with M42 thread available, I consider getting one of those. I read that the the distance added by the required adapter can move the lens too far from the sensor, so that infinity focus cannot be achieved anymore? Is this true? Any experiences with this? 

 

Thanks

Sven

[Alien 13]

M42 lenses are normally fine for Canon cameras with the correct adapter but might not work with a modified one, these lenses will not be compatible with any Nikon the back focus is too long.

Alan

[Gina]

There are plenty of superb vintage 42mm x 1mm Asahi Pentax Takumar, Super Takumar and SMC Takumar lenses on ebay.    But camera lenses are best suited to NB imaging as the correction for chromatic aberration does not extend far into the red.  This is/was because the human eye is less sensitive to detail at the red end of the spectrum. 

[Ludd]

I have used an ancient Pentax 135mm lens happily on my Canon cameras, no problems with focus. Mind you, my recently acquired modded camera has a Baader filter fitted; not sure whether that would work if no filter is fitted. If you were nearby, rather than in Germany, I would lend it to you for testing. 

[happy-kat]

If your nodded camera can still achieve infinity focus with the kit lens then I expect it would with an eos-m42 adapter as the sensor probably was shimmed as part of the mod. Can't garuentee that as making a guess.

[freiform]

7 hours ago, Gina said:

There are plenty of superb vintage 42mm x 1mm Asahi Pentax Takumar, Super Takumar and SMC Takumar lenses on ebay.    But camera lenses are best suited to NB imaging as the correction for chromatic aberration does not extend far into the red.  This is/was because the human eye is less sensitive to detail at the red end of the spectrum. 

Those lenses look nice. I thought that CA isn't that much of a problem with very widefield images, i.e. 10 - 35 mm focal length? 

 

54 minutes ago, Ludd said:

I would lend it to you for testing.

That is nice of you ;). 

 

I guess I'll order a cheap lens to see if I can focus properly and then head for a more permanent investment like those Takumars mentioned by Gina.

[Gina]

22 minutes ago, freiform said:

Those lenses look nice. I thought that CA isn't that much of a problem with very widefield images, i.e. 10 - 35 mm focal length?

You might be right - I'm not sure.  But I may find out when I manage some imaging

[happy-kat]

My 50mm super takumar even wide open f2.2 doesn't have any CA.

[RichLD]

If the lenses don't have ED or similar elements, be prepared for bloat, especially on blue stars and less so on red when broadband imaging. As @Gina said, you will get much better results using camera lenses for NB.

To explain a little more, if I use my Super Takumar (non-ED) lenses to take a broadband AP image and I have focussed using a Bahtinov mask, if I split the channels into RGB the green channel is in focus, the red channel is slightly OOF and the blue channel is more OOF than the red channel.

If I perform the same experiment with my Nikkor ED180 (ED) lens, the RGB channels all have good (similar) focus - it's the ED elements that make the difference of course.

HTH

Rich