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11-07-2010, 11:07 PM   #1
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Pentax K-5 mirror question (for owners and people in the know)

Howdi folks,

in my infinite stupidity I have forked out a lot of money for a Leica Summilux-R 35/1.4 which has a pretty prominent rear element. It hasn't arrived yet but I have a funny feeling that it will interfere with the mirror on my K20D.

Hence this question - is the mirror on K-5 smaller/less prominent? What about K-7?

Should I sell the car and get one of those?


Last edited by DanielT74; 11-14-2010 at 07:09 PM.
11-07-2010, 11:22 PM   #2
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All 3 cameras use the same mirror. I doubt it'll hit the element on your lens, though. The distance is greater than you might think.

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11-08-2010, 02:17 AM   #3
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Thanks, Adam!

There goes this excuse to buy the K-5 now Never mind - I will think up some more!)

David from Leitax told me that the Summilux can't be adapted to Nikon for this reason and he wasn't sure about Pentax, so we may be making history here!
11-08-2010, 04:45 AM   #4
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QuoteOriginally posted by DanielT74 Quote
Leica Summilux-R 35/1.4 which has a pretty prominent rear element. It hasn't arrived yet but I have a funny feeling that it will interfere with the mirror
As said, all Pentax APSC have about the same mirror dimensions. If any, the K-7/5 may be a tad larger because of 100% VF.

Here is a cut thru a K-5:

(click to enlarge)

You see axis and edge of mirror and you can draw a circle of the mving mirror. If you can get a drawing of the Summilux, just overlay it in Photoshop and you have an easy verification if the mirror will hit the lens -- without actually trying it and risking the damage.

Enjoy!

11-08-2010, 07:09 PM   #5
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Thanks, Falk!

Hmmm... maybe, what do you think?

11-08-2010, 07:21 PM   #6
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Isn't that lens designed for the Leica M8 which I would imagine has a shorter register distance than a DSLR? If that's the case it won't be usable even if you could fit it. If the register distances fit, then the next challenge is finding an adapter that would allow the lens to be mounted on a K-mount camera.
11-08-2010, 07:30 PM   #7
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No, no, this is a summilux-r, for the R-bodies. The r-lenses are usually adaptable to Pentax bodies (just adapted summilux-r 50/1.4 and summicron-r 35/2). But there may be bits sticking out too far...

Last edited by DanielT74; 11-08-2010 at 07:35 PM.
11-08-2010, 08:15 PM   #8
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I understand that this is a problem with some Canon kit; the problem with Canon's is (as I half remember it) is between FF and APS bodies and EF and EF-S lenses. I think the way it goes is, EF lenses will fit APS bodies, but the mirror shatters when it hits the back of the lens.


Last edited by rod_grant; 11-08-2010 at 11:14 PM.
11-09-2010, 05:20 AM   #9
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QuoteOriginally posted by DanielT74 Quote
Thanks, Falk!

Hmmm... maybe, what do you think?
Why didn't you do the photoshop job?

The overlap is about 2mm (I already corrected for the wrong curvature in the lens image). So, it wouldn't work.

But to really confirm the 2mm impact area, you'll need to come up with a better drawing of the lens. You need a technical drawing and I think, Leica has it somewhere. At least, this is what Zeiss does. Also, who says you would mount the Leica at the same registration distance? After all, the Leica R camera has a mirror too...
11-09-2010, 02:51 PM   #10
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QuoteOriginally posted by falconeye Quote
Why didn't you do the photoshop job?

The overlap is about 2mm (I already corrected for the wrong curvature in the lens image). So, it wouldn't work.

But to really confirm the 2mm impact area, you'll need to come up with a better drawing of the lens. You need a technical drawing and I think, Leica has it somewhere. At least, this is what Zeiss does. Also, who says you would mount the Leica at the same registration distance? After all, the Leica R camera has a mirror too...
Well, it was a photoshop job, just a very poor one! Or did you mean something else?

But of course, the dimensions are important here and though I resized the picture I had, it was a very rough guess.

My plan is to measure the exact distance the rear element protrudes once the lens arrives, make a cylinder on a plane out of paper that protrudes the same distance (or a millimeter more to account for error) and put it on the camera. Then to press the shutter release a few times to see if the paper bit gets touched by the mirror.

What do you think?
11-09-2010, 03:06 PM   #11
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If your photo is scaled properly,it will definitely hit the lens.
11-09-2010, 03:40 PM   #12
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QuoteOriginally posted by Frederick Quote
If your photo is scaled properly,it will definitely hit the lens.
That's my thinking too. Leica R mount is a touch bigger than K mount, so I scaled it with this in mind.

But... there may be a rubber ring on the rear element that could be taken off. This could save a millimeter or so. Will see!

QuoteQuote:
Also, who says you would mount the Leica at the same registration distance? After all, the Leica R camera has a mirror too...
Could you clarify what you mean here, Falk?
11-09-2010, 04:38 PM   #13
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QuoteOriginally posted by DanielT74 Quote
Well, it was a photoshop job, just a very poor one! Or did you mean something else?
I meant constructing a circle (in PS) with given axis (as seen in the cut model shot) and radius. And drawing a rectangle to represent a cut through the rear lens element. I then get a 2mm overlap. So, you need more precision as this is in the tolerance of the method.

I would put the body in sensor cleaning or mirror lockup mode and then mount the lens. Much less danger for damage if the mirror is only halted on swinging down. At least I would asssume.

QuoteOriginally posted by DanielT74 Quote
Could you clarify what you mean here, Falk?
You place the lens at the K-mount bajonett. But an R mount has a mirror too, a larger full frame mirror that is. With the rear lens protruding this much, maybe the R mount registration distance is larger? Why else shouldn't the lens touch the mirror in a Leica camera? And if so, the lens wouldn't sit directly on the K-mount bajonett but would require an adapter or modification to compensate. After the adpation, you should have gained the 2mm and more.

I just looked it up:
K-mount registration distance: 45.46 mm
R-mount registration distance: 47.00 mm

Difference: 1.54 mm. Which means that the overlap reduces to 0.46 mm.

Now, you really need to work with more precision on all of this. It's a question of one mm. No way you can make your paper model 1 mm larger than needed

Last edited by falconeye; 11-09-2010 at 04:43 PM.
11-09-2010, 05:28 PM   #14
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I am quite ignorant of these things. Thank you for walking me through the relevant facts, for engaging in this little problem and for the tips.

I didn't do the circle because visually it appears to hit and at this level of precision (as you said) I didn't think drawing would be decisive.

Not quite sure how one would go about putting something between the mount and the lens (if necessary). I guess one could find some little washers to put where one screws the mount and then lose the aperture clicking in place which is not the end of the world (one would "see" it in AV mode from the changing exposure times).

The lens should be here early next week, I anticipate. Friday, if I am lucky. I will keep everyone posted!

In the meantime if you have more ideas/info to share, please do - it's already been very interesting!
11-09-2010, 06:26 PM   #15
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QuoteOriginally posted by DanielT74 Quote
Not quite sure how one would go about putting something between the mount and the lens (if necessary). I guess one could find some little washers [...]
I'm sure you have an idea how to mount the lens to your Pentax.

I guess you follow along the lines described by Leitax. I then assume that the registration distance is converted as part of the adaption. And this gains you 1.5mm, if the image is from an original R-lens. Enough to make it a close tie.
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