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09-26-2011, 05:47 AM   #1
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Yashica Yashinon DX 50mm 1.7 - does it damage mirror?

Hi. I just won a Yashica Yashinon DX 50mm 1.7. I read one post that the back of the lens can hit the camera mirror when used on a K20D. Has anyone here had this experience?

09-26-2011, 05:54 AM   #2
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QuoteOriginally posted by Spodeworld Quote
Hi. I just won a Yashica Yashinon DX 50mm 1.7. I read one post that the back of the lens can hit the camera mirror when used on a K20D. Has anyone here had this experience?
I never tried it on my K20D but it works fine on my K10d which should be identical to the K20D in term of camera mirror distance. Furthermore. the Yashinon DX 50/1.7 is a typical M42 like any others so I don't really see why it would hit the mirror of the K20D.
09-26-2011, 06:04 AM   #3
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It works fine on my k-x
09-26-2011, 06:17 AM   #4
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Thanks guys. I got a little concerned because of this post: YashicaForum.com • View topic - Auto Yashinon-DX 50mm f1.7 (see last post)

If the problem exists, it is because of about 1mm @ infinity focus.

09-26-2011, 07:26 AM   #5
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Steve, as I haven't had any problems with any of my m42 lenses, I haven't looked at it to closely. I see you have other m42 lenses, do any of them have the A/M switch, and can you compare them? What I would do, is fit the adapter on the lens, and measure the distance from your mirror to the front of the camera mount, and the distance from the front of the adapter to the back of the lens, and that should give you an indication if the clearance might be a problem on your camera.
09-26-2011, 08:14 AM   #6
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Not sure how to measure from the mirror on out to the camera mount...sounds a bit risky to me going that close to the mirror, espcially as it is down to the mm. Perhaps this information is available.

Maybe I'll compare the Yashica to my Super Takumar 50mm 1.4 and see if one extends further back at infinity. I haven't noticed any problems with the Super Tak....yet

QuoteOriginally posted by altopiet Quote
Steve, as I haven't had any problems with any of my m42 lenses, I haven't looked at it to closely. I see you have other m42 lenses, do any of them have the A/M switch, and can you compare them? What I would do, is fit the adapter on the lens, and measure the distance from your mirror to the front of the camera mount, and the distance from the front of the adapter to the back of the lens, and that should give you an indication if the clearance might be a problem on your camera.
09-26-2011, 08:37 AM   #7
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Unforunately I will only be able to have a look at mine tomorrow, (5.30pm where I am now, and still at work)
QuoteOriginally posted by Spodeworld Quote
Maybe I'll compare the Yashica to my Super Takumar 50mm 1.4 and see if one extends further back at infinity. I haven't noticed any problems with the Super Tak....yet
That should also be able to do it. let us know if and what the difference is, if any.
09-26-2011, 09:06 AM   #8
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QuoteOriginally posted by Spodeworld Quote
Thanks guys. I got a little concerned because of this post: YashicaForum.com • View topic - Auto Yashinon-DX 50mm f1.7 (see last post)

If the problem exists, it is because of about 1mm @ infinity focus.
I might try it on one of my not-valuable film cameras. The K mount registration distance is the same as M42, so an M42 lens shouldn't interfere with the mirror. The mirror on the K20D is smaller than one on a film camera, because it only has to be APS-C sized. If it works on a K-mount film camera, it should work on the K20D.

09-26-2011, 09:33 AM   #9
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My M42 Yashinon-DX 50/1.7 fits on my K20D with no problem.

To tell if any M42 lens might interfere with a SLR's mirror, whip out a plastic ruler. Measure the camera's depth from mount to mirror box -- that should be around 13mm on ANY Pentax body. (I have so measured my K20D, ZX-M, MV1, and K1000.) Now measure the depth of the lens rear element from the lens base. I have yet to find an M42 lens that extends more than about 9mm from the base.

I modded a Petri lens by removing its bayonet and gluing-on a cheap M42-PK adapter as a replacement base; its rear element extended about 9mm. Still lots of space between element and swinging mirror -- no problem!

I can think of one sort of M42 lens that probably will NOT work on a Pentax SLR, the lenses made for the Krasnogorsk 16mm cine cameras. I've read that the cine M42 lenses extend too far. So just avoid those tempting wide Jupiter zooms and you'll be fine!

Last edited by RioRico; 09-27-2011 at 07:07 AM.
09-26-2011, 10:27 AM   #10
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Thanks guys....great feedback. So, it looks like 13mm is the measurement to use, but the collective experience here is that it has been used on the K20D with no problems. Interesting about the post that I linked to. I wonder what really happened????
09-26-2011, 10:40 AM   #11
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QuoteOriginally posted by Spodeworld Quote
Thanks guys....great feedback. So, it looks like 13mm is the measurement to use, but the collective experience here is that it has been used on the K20D with no problems. Interesting about the post that I linked to. I wonder what really happened????
That's a good question! I just read that post, and then I measured my DX50/1.7, and it extends... about 9mm at infinity focus, its deepest. I don't see any way the DX could be modded to make it extend any further. Yes indeed, what really happened???
09-27-2011, 02:54 AM   #12
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As usual Rio is on the dot! I measured the lens at maximum 9.45mm with a caliper, and mount to mirror box 13mm, so there should not be any problem.
QuoteOriginally posted by Spodeworld Quote
I wonder what really happened????
With more than 3.5mm to play with, it would be interresting to get an answer to that one
09-27-2011, 03:24 AM   #13
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Ok, so I joined the club and asked the bloke how it happened that his mirror hit the lens. A moderator must first approve the post before publishing it, so we'll wait and see if we can solve this mistery!
09-27-2011, 03:39 AM   #14
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DX 50mm f1.4 collects the mirror on a K20, can't say about the 50mm f1.7 having never owned one. Had one and sold it for that reason.
09-27-2011, 05:39 AM   #15
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@xjjohnno - That's interesting. So the DX 50mm f1.4 can damage the mirror. But the Super Tak 50mm f1.4 doesn't seem to as far as I can tell. This must mean that the f1.4 Yashica extends further than the equivalent 1.4 Takumar.

@altopiet - Looking forward to hearing what happened. Good idea joining the conversation to find out. But it seems he feels that the lens was the problem unless he got new information.
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