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09-03-2007, 12:07 PM   #1
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Screw mount lenses for K10D

Are all screw mount Pentax/Takumar lenses M42 mounts? Are all M42 mounts the same? With a Pentax M42 ring will they all fit on a K10D? With one of these lenses and a Pentax M42 ring, are they all manual everything? Would I be correct to look for a Pentax ring as opposed to a generic one? I recall reading about some who have had problems with a generic ring getting stuck in their camera. Thanks for your advice.

CN


Last edited by Clem Nichols; 09-03-2007 at 12:09 PM. Reason: Additional question
09-03-2007, 03:43 PM   #2
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I'm on this path with a K100D
enjoy


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09-03-2007, 04:14 PM   #3
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you can get adapters from adorama and b & h for around 18usd delivered. get the kalt or the bower. they work fine. the adapters have a bottom and top ring on them. the ones that work have about the same size bottom and top flange. the ones that obviously have a protruding(larger) flange will not let you focus to infinity.. this will WORK
this will NOT
09-03-2007, 05:27 PM   #4
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Roy:

Thanks for the info. I'm probably mistaken, but it seems that I came across a thread either here or on dpreview that said something about a genuine Pentax brand M42 ring allowing automatic aperture control. Intuitively, I'd have to think that wasn't the case. Do you know? Also I see that the "will work" adapter for sale on E-Bay has a tool which comes with it for removing the ring, and the ones at B&H apparently don't have. Is a tool necessary? Thanks for your help.

CN


Last edited by Clem Nichols; 09-03-2007 at 05:55 PM. Reason: Additional info
09-03-2007, 07:20 PM   #5
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Roy:
I have the Pentax ring (from local camera store) and it works like a charm. It does not come with a removal tool, but a fingernail or a small screwdriver blade is all it takes to release the lock spring. When installed, you can expect your m42 lenses to mount/unmount easily and to focus to infinity. The automatic aperture function will be disabled, so your lens should have the auto/manual slider or have manual/preset aperture in order to shoot other than wide-open.

On the K10D you can use either aperture priority auto exposure or manual (stop-down) exposure using either the "green" button (camera sets the shutter speed) or the stop-down switch (camera tells you +/- correct exposure in the viewfinder). The only problem is that metering is generally only accurate in the range of f5.6 - f8.0. Wider apertures yield 1-2 EV under-exposure and small apertures yield 1-2 EV over-exposure. This is a well-documented "feature" of the K10D that has something to do with the light-box, sensor placement, and focus screen when used with K, M, or m42 lenses. Best practice is to make a couple of test shots and examine the histogram to determine how to bias the exposure. Either that or use a hand-held meter.

Despite the hassle, the rewards are significant. The old glass is MUCH nicer to work with that much of the newer stuff.

Steve

Last edited by stevebrot; 09-03-2007 at 07:31 PM. Reason: Better grammar
09-03-2007, 07:49 PM   #6
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Thanks, Steve.

CN
09-04-2007, 12:24 AM   #7
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QuoteOriginally posted by Clem Nichols Quote
Roy:

Thanks for the info. I'm probably mistaken, but it seems that I came across a thread either here or on dpreview that said something about a genuine Pentax brand M42 ring allowing automatic aperture control. Intuitively, I'd have to think that wasn't the case. Do you know? Also I see that the "will work" adapter for sale on E-Bay has a tool which comes with it for removing the ring, and the ones at B&H apparently don't have. Is a tool necessary? Thanks for your help.

CN
The one that I ordered, the bower general m42 adapter, do come with a tool that is needed to mount and dismount the adapter. I have my m42 adapter for two days so far it works out quite well for me. Unlike the genuine pentax adapter which I can't find it anywhere, the adapter in the link requires a key for mounting and dismounting. So far, I find it quite manageable for the mounting as long as I have that tool with me.

General Brand | Pentax-K Body to Universal Lens Adapter | B&H


Picture and description from PhotoPete for the general adapter along with the genuine one that comes with a key in the picture. I hope Pete forgives me in using his picture as I have asked him for usage and I have not heard back from him. I intend to use his picture in future references.


Left to Right : Adaptor Tool -> Genuine Pentax M42 adapter -> third party adapter

Thanks,
Hin
09-04-2007, 02:26 AM   #8
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I use the M42 lenses almost exclusively. Mostly because I can get good glass at bargain prices, but also because I love using "obsolete" equipment.

M42 lenses are not all the same. There are some which have a small, almost unnoticiceable pin which must be depressed before you can move the auto/manual slider to the manual position. There is a post about this in one of the stickies here. Once you're in manual, though, there is no difference as far as using them goes.

I use the K100D, which is not the same as the K10D as far as exposure issues go. The K100D also underexposes M42 lenses, but it does so consistently across the aperture range. That consistency is a blessing.

I recently learned from a post here of a very good tip for working around the underexposure issue. It involves placing some aluminum foil across the contacts on the front of the camera. I started doing it yesterday and now have a piece of foil taped on the front of the camera, with the foil going up onto the adapter so the lens body can help in holding the foil in place. This reduces the underexposure so that I only need to set the EV adjustment to +0.3 ~ +0.7, leaving me some latitude for adjusting for backlit situations. My 55/1.8 seems to like it better at +1.

09-04-2007, 04:53 AM   #9
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clem,
i ordered the kalt from B&H and it did come with the tool. all i need to remove it is my thumbnail. of course my nails are like sheet metal..
09-04-2007, 04:54 AM   #10
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QuoteOriginally posted by stevebrot Quote
Roy:
I have the Pentax ring (from local camera store) and it works like a charm. It does not come with a removal tool, but a fingernail or a small screwdriver blade is all it takes to release the lock spring. When installed, you can expect your m42 lenses to mount/unmount easily and to focus to infinity. The automatic aperture function will be disabled, so your lens should have the auto/manual slider or have manual/preset aperture in order to shoot other than wide-open.

On the K10D you can use either aperture priority auto exposure or manual (stop-down) exposure using either the "green" button (camera sets the shutter speed) or the stop-down switch (camera tells you +/- correct exposure in the viewfinder). The only problem is that metering is generally only accurate in the range of f5.6 - f8.0. Wider apertures yield 1-2 EV under-exposure and small apertures yield 1-2 EV over-exposure. This is a well-documented "feature" of the K10D that has something to do with the light-box, sensor placement, and focus screen when used with K, M, or m42 lenses. Best practice is to make a couple of test shots and examine the histogram to determine how to bias the exposure. Either that or use a hand-held meter.

Despite the hassle, the rewards are significant. The old glass is MUCH nicer to work with that much of the newer stuff.

Steve
welcome to the board steve!!
09-04-2007, 05:15 AM   #11
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QuoteOriginally posted by Clem Nichols Quote
Roy:

Thanks for the info. I'm probably mistaken, but it seems that I came across a thread either here or on dpreview that said something about a genuine Pentax brand M42 ring allowing automatic aperture control. Intuitively, I'd have to think that wasn't the case. Do you know? Also I see that the "will work" adapter for sale on E-Bay has a tool which comes with it for removing the ring, and the ones at B&H apparently don't have. Is a tool necessary? Thanks for your help.

CN
I have strange experiences with M42 adapters.

With Takumar lenses, the original Pentax adapter works so precisely that I removed the locking pin from the adapter. This allows me to mount and unmount the lenses as if they were bayonet rather than screw.

With the Kalt adapter, over time it has worn down and now can sometimes accidentally over-rotate. This of course only causes a mild heart attack to me and doesn't do damage to the camera.

However, I have since picked up a few Russian lenses (under the Jupiter and Helios names) and strangely the original Pentax adapter will not screw on to the mount, but the Kalt adapter (and other third-party adapters) will! I'm a bit perplexed by that one.

One more strange tidbit is that my huge Jupiter-6 lens must have had the infinity point moved, because I can successfully use one of the flanged adapters on it. If you're resourceful you can adjust the infinity point on all your lenses. The upside is that the flanged adapters behave like K lenses (meaning you can use the 1.7x AF Converter, the flange acts like the aluminum foil trick) and the flanged adapters lock and unlock just like a real bayonet. They are also cheaper. The downside is that you have to know how to adjust the infinity focus point.

--Sean
09-04-2007, 08:19 AM   #12
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Thanks Hin, Mike, Sean, et al for your response. You've helped to clear up much of my ignorance regarding screw-mount lenses, their adapters, and how to use them on my K10D.

CN
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