advice please on smallest 20mm m42 lens

[rbelyell]

hi

i need some help as i want to acquire a very small 19-21mm prime in m42 mount. i had the mir 21/4. it was too big and had too much distortion. so my wants:

1. MUST be m42 (please do not suggest great non m42, it won't help me!)

2. must be smaller than the mir

3. would really like low distortion/good resolving power

thank you!
tony

[Attila]

It is not exists...

[F16SUNSHINE]

Agree with Attila
In M42 there is nothing for you at 21.
If you can go to OM then a Zuiko 3.5/21 is a super choice.
Otherwise go up o 24mm and search for a Yashica DSM 2.8/24.
From all I could tell it's the same lens as the ML 2.8/24mm which you own so, you know how big it is.

[natebarnz]

I have no experience with it but you might want to try a Mamiya Sekor 21/4 in m42. Or just go with a Flek, it won't cut down on size but it will likely improve your IQ over the Mir.

[lEo.]

Lucispictor metioned Cosina 20/3.8 from

http://www.flickr.com/groups/m42/discuss/72157621789610856/

[rbelyell]

anyone use the tak 20/4.5, that looks small...

[themoleman342]

I've used the S-M-C Tak 4.5/20mm. It does certainly fit the small requirement. It's about the same size as the Tak 24mm. Front thread is only 58mm. The original hood is huge though.

I honestly was not that impressed with it. Maybe I expected too much. The corners on my copy were never good, even at f8. That was with film. Wide open they were like mud. Distortion was no better controlled than with the Mirs.

Focusing was impossible in anything other than full sunlight too. Could have been the Pentax ES, which certainly doesn't have the brightest screen but it isn't the worst. I guess the expectation with a 20mm is that by stopping down to f11 or f16 and setting it to the hyperfocal distance you have essentially a point and shoot. I didn't like doing that. Felt like I had no control.

But center sharpness and colors were good. So was flare protection and contrast. The S-M-C was probably one of the best coatings you can find on an older super-wide.

[luisalegria]

A 20-21mm SLR lens in those days was most commonly a non-retrofocal type with the optics poking far into the mirror box, used with the mirror locked up and an external finder. Most of the SLR makers had something like that - Nikon, Yashica, etc. Focusing was by scale.

This wouldn't work on Pentax Spotmatics as they lacked mirror lock-up (or mostly did). So Pentax had to do it differently and try to get a good retrofocus solution.

The Pentax was a bit out of the ordinary back in the day. The retrofocus alternatives were huge, and pretty poor - except for the Zeiss Flektogon.

A 4.5/20 is indeed a very difficult lens to focus accurately on an SLR. From my experience the best way to use these is in fact by scale/hyperfocal focusing, if the scale is accurate.

[F16SUNSHINE]

[Tervueren]

one of the smallest i've seen is the om 21/f2, very expensive and you would either need an adapter or convert the mount if it's possible

[trev]

My Vivitar 19 3.8 is pretty much small and not a bad performer either

[Aanything]

The already mentioned mamiya sekor sx 21/4 is small, and should be a good lens. Not so easy to find and not extremely cheap, and somewhat tricky to adapt, but probably one of the best in that range and mount.