Takumar SMC 200mm F4 - not quite infinity and beyond

[John78]

I bought one of these lenses and an ebay £3 M42-EOS adapter I could find and I've been testing it tonight - when focused hard to infinity its ever so slightly soft, it needs to be closer...

Am I being too fussy? Vega, wide open 5sec ISO 1600 shot on a static tripod ...

Looking at this website...

http://k10dpentax.blogspot.co.uk/2008/05/fixing-infinite-focus-on-super-takumar.html

I could adjust the lens - is there a better/more indepth guide?

Anyway I 3D printed a bahtinov and measured it at the best focus and as expected its very slightly out - I also measured the length of the lens with a caliper

Current best focus @ infinity :-

Intentionally slightly out :-

My maths tells me (assuming the relationship is linear), I am 133uM short of best focus (4px out and 27.1px out, 0.77mm lens length increase).

The M42-EOS adapter front face that sticks out of the body is 1.34mm thick - so if I face it off in a lathe down to 1.207mm the focus should be perfect, the lens will screw on a smidge closer to the body.

Although it might be advantaged just to turn it down to 1mm then the lens will be definitely able to focus past infinity in all situations (temperatures)??

 

Turning down the adapter seems like a significantly easier mod than disassembling the lens?  Thoughts?

[Thalestris24]

Hi

From memory, you just need to undo/loosen the tiny screws that go around the central barrel. You'll need a jeweller's screwdriver set. Then you just turn it clockwise (I think!) and put/tighten the screws back.

My Takumar 200mm is quite good for astro but has a slight problem with the red wavelengths though at 200mm it's hardly noticeable. It might work better stopped down one stop. However, I've only ever used mine at F4. Somewhere on here you might find my original posts when I faced the same problem

Good luck!

Louise

[Alien 13]

If you turn your lens side on with the adapter fitted is the body flush with the adapter face?, you can gain a little by just removing material from the inner edge of the adapter,

Alan

[alacant]

6 hours ago, Thalestris24 said:

you just turn it clockwise

Hi. Other way. Looking from above, anticlockwise. No need to dismantle. Loosen the three screws which fix the focus barrel and turn. 1/4 turn anti. Also make sure that your adaptor does not have a flange -or file the pin, otherwise the lens sits tilted. If you don't want to do any adjustment, get one of the thinner adjustable adatpors and remove the flange. See attached. Without flange and adjustable with flange but thinner. HTH

[Thalestris24]

41 minutes ago, alacant said:

Hi. Other way. Looking from above, anticlockwise. No need to dismantle. Loosen the three screws which fix the focus barrel and turn. 1/4 turn anti. Also make sure that your adaptor does not have a flange -or file the pin, otherwise the lens sits tilted. If you don't want to do any adjustment, get one of the thinner adjustable adatpors and remove the flange. See attached. Without flange and adjustable with flange but thinner. HTH

Ha - I knew it was one way or the other! What make is the second adapter? Is there one for a Canon EOS? I've not seen one like that before

Louise

[John78]

3 hours ago, Alien 13 said:

If you turn your lens side on with the adapter fitted is the body flush with the adapter face?, you can gain a little by just removing material from the inner edge of the adapter,

Alan

If I take material from the camera body edge of the adapter it looks like it would be loose, the camera edge will allow me to screw the lens in further was my thinking.

45 minutes ago, alacant said:

Hi. Other way. Looking from above, anticlockwise. No need to dismantle. Loosen the three screws which fix the focus barrel and turn. 1/4 turn anti. Also make sure that your adaptor does not have a flange -or file the pin, otherwise the lens sits tilted. If you don't want to do any adjustment, get one of the thinner adjustable adatpors and remove the flange. See attached. Without flange and adjustable with flange but thinner. HTH

3 screws and anti-clockwise sounds a lot easier than that link made it look, for Astro it's better to be able to focus past infinity to ensure perfect focus, I'll give it a go later today it sounds like an easy mod.  

 

Thanks everyone.

[alacant]

35 minutes ago, John78 said:

sounds a lot easier than that link made it look

Hi. The 200mm isn't that construction. HTH.

[alacant]

34 minutes ago, Thalestris24 said:

Is there one for a Canon EOS

Hi. Yes. The photo is m42-eos, available here and on ebay. (or 4 times the price from walk in dealers!). HTH.

[John78]

So while waiting for the shower this morning I gave it a quick adjust - there's no way to get 1/4 of a turn on it (I concur CCW is the required direction) but I did get about 1/12th which has shrunk the lens by ~1.3mm I'll test it again tonight but it looks like it goes past infinity now.

[Thalestris24]

4 hours ago, alacant said:

Hi. Yes. The photo is m42-eos, available here and on ebay. (or 4 times the price from walk in dealers!). HTH.

Thanks! Amazon UK do them (by Xcsource)

[alacant]

1 hour ago, Thalestris24 said:

Amazon UK do them

 One last thing is to file a 'V' in the flange so the pin is not compressed. Check you get the right place by adjusting the lens in the position you want it when screwed home -usually with the f number and distance scale facing upwards-. HTH

[Thalestris24]

Hi

I don't understand about the pi - mine looks like this:

The pin doesn't seem to interfere with anything?

Louise

[alacant]

Move the lens to infinity...

[John78]

Yeah the aperture pin never touches anything there is another pin which sits on the adapter ring but that doesn't seem to do anything either, I'm confused.

 

Ive just noticed a spec of dust on my images that appears to be on the bottom of the clear filter on the sensor, must have been during Astro modding ?

[John78]

Can confirm can now focus to infinity and beyonddddddd

[Thalestris24]

1 hour ago, alacant said:

Move the lens to infinity...

?

[alacant]

Hi. The op has the smc. I think yours is the super. Are you sure that the pin doesn't contact the flange when you screw the lens focusing barrel to infinity? Here's my smc 200:

 

**edit. OK. I see now. You have the correct adaptor -without the flange- attached to the lens. The new one will have a flange which interferes with the pin. That's what I meant by file a bit off the flange. The adaptor you have doesn't have a flange. Sorry. Too much work and not enough astronomy. HTH. 

 

[alacant]

2 hours ago, John78 said:

I'm confused

Hi. Takumar lenses must have the straight through adaptor, not the ones with a flange. Even though it doesn't look as if it intrudes on the flanged adaptors, it causes the lenses to sit with a slight tilt as the flange depresses the pin, but the pin's stop comes before the lens is screwed home. If you have a flanged adaptor, you can file a groove so that the pin does not get compressed by the flange when the lens is screwed home. If you have a lathe you can remove it completely:) Please see this post.

[John78]

1 hour ago, alacant said:

Hi. Takumar lenses must have the straight through adaptor, not the ones with a flange. Even though it doesn't look as if it intrudes on the flanged adaptors, it causes the lenses to sit with a slight tilt as the flange depresses the pin, but the pin's stop comes before the lens is screwed home. If you have a flanged adaptor, you can file a groove so that the pin does not get compressed by the flange when the lens is screwed home. If you have a lathe you can remove it completely:) Please see this post.

Yes understand, my auto pin is free it touches nothing when the lens is screwed on same as Louise's picture.

My lens rattles I realise, something must be loose, but it doesn't appear to effect any functions nor is it visible anywhere, for £35 and working I'm not sure it's worth disassembling.