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08-20-2013, 05:55 AM   #16
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So buy an m42 adapter (get a decent one, a bad adapter will cause you more headaches than you save money) and then be sure to post some photos of your new moon

08-20-2013, 06:25 AM   #17
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used equipment - How do I identify unknown thread mounts? - Photography Stack Exchange
"At 42mm, the mount could be either M42 (Pentax/Practica/Zeiss) or T-mount. The difference is thread pitch -- the M42 has a 1mm thread pitch (the "wavelength" of the thread, measured from "peak to peak"), and the T-mount has a 0.75mm thread pitch. So, three grooves in three millimeters is M42; four grooves in three millimeters is T-mount (or one of the variations on T, like the Sigma YS)."
08-20-2013, 06:55 AM   #18
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QuoteOriginally posted by altopiet Quote
used equipment - How do I identify unknown thread mounts? - Photography Stack Exchange
"At 42mm, the mount could be either M42 (Pentax/Practica/Zeiss) or T-mount. The difference is thread pitch -- the M42 has a 1mm thread pitch (the "wavelength" of the thread, measured from "peak to peak"), and the T-mount has a 0.75mm thread pitch. So, three grooves in three millimeters is M42; four grooves in three millimeters is T-mount (or one of the variations on T, like the Sigma YS)."
I've seen multiple references to this "difference" between m42 and T, but I have lots of T-mount adapters and lots of M42 cameras and adapters, and lots of m42 and T mount lenses, and they have all always been able to interchangeably thread with each other with no noticeable issues, and no damage to either side. How is that possible if the thread pitch is 25% different?
08-20-2013, 03:16 PM   #19
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QuoteOriginally posted by thornburg Quote
I've seen multiple references to this "difference" between m42 and T, but I have lots of T-mount adapters and lots of M42 cameras and adapters, and lots of m42 and T mount lenses, and they have all always been able to interchangeably thread with each other with no noticeable issues, and no damage to either side. How is that possible if the thread pitch is 25% different?
Having personally had to remove a M42 adaptor jammed on a T mount lens I don't know how this is possible either.
they simply don't go more than about half a turn.

08-20-2013, 03:39 PM   #20
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QuoteOriginally posted by skunktail Quote
Having personally had to remove a M42 adaptor jammed on a T mount lens I don't know how this is possible either.
they simply don't go more than about half a turn.
Might that not be part of the problem? If it is only partially screwed in you would lose infinity focus even more than the different registration distance of the mount would cause.
08-20-2013, 03:49 PM   #21
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You can actually see a Moon shot with the Optomax 400mm on a Pentax K10D here:

Optomax 400mm 6.3 | Flickr - Photo Sharing!

and a bird shot from the same photostrem:

Optomax 400mm 6.3 | Flickr - Photo Sharing!

So do get yourself an M42 adapter for your camera body and have fun - but I very much agree: Be carefult with those cheap Chinese ones. There are many reports that they may get jammed in the camera body and/or that there flanges are too thick to reach infinity focus.

The genuine Pentax Mount Adapter K (P30120) may be more expensive, but it works - and it is safe!
08-20-2013, 04:24 PM   #22
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Sigma 150-500.
08-20-2013, 08:02 PM   #23
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QuoteOriginally posted by skunktail Quote
Having personally had to remove a M42 adaptor jammed on a T mount lens I don't know how this is possible either.
they simply don't go more than about half a turn.
I've freely threaded T2 lenses on M42 adapters and M42 lenses on T2 adapters. Never jammed, never any problems. I'm so confused.

08-21-2013, 02:17 AM   #24
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QuoteOriginally posted by thornburg Quote
I've experienced this exact same problem myself, with a Vivitar branded 400mm lens.

The problem is you're using a T-mount adapter, but it's actually an M42 lens. M42 and T use the same thread (so you can physically screw them in to either one), but the T-mount is much thicker. An m42 adapter should be very thin.

The T-mount adapter basically acts as a tiny extension tube for an m42 lens, which shortens the minimum focus distance, but you lose infinity.

BH has m42 adapters for about $30. eBay has cheap chinese ones for around $5.

I do have two adapters with that lens an they can be screwed into each other. This probably is the thing then...
08-21-2013, 08:18 AM   #25
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Guys, is this adapter suitable? Will it allow to focus infinity?
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08-23-2013, 11:08 AM   #26
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It looks like it probably will, but I can't guarantee it. But keep in mind that adapter needs that tool (the thing on the side) to be removed from the camera. The genuine Pentax adapter doesn't need a tool, you can do it with your finger nail, so you can do it quickly, on the spot.
For adapters, it is best to try to google the brand and see if someone wrote about it. If it has no brand name, it is probably so cheap that you can afford to risk it. But it might take up to a couple months for it to get delivered from China, and it might get stuck on your camera (every once in a while we get a freakout thread, where someone is having problems removing an adapter. In some cases they can get it off without problems, in others, they have to disassemble the camera mount). But on the other hand, most people use unbranded adapters just fine, with no problem at all.
08-23-2013, 02:15 PM   #27
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QuoteOriginally posted by Na Horuk Quote
It looks like it probably will, but I can't guarantee it. But keep in mind that adapter needs that tool (the thing on the side) to be removed from the camera. The genuine Pentax adapter doesn't need a tool, you can do it with your finger nail, so you can do it quickly, on the spot.
For adapters, it is best to try to google the brand and see if someone wrote about it. If it has no brand name, it is probably so cheap that you can afford to risk it. But it might take up to a couple months for it to get delivered from China, and it might get stuck on your camera (every once in a while we get a freakout thread, where someone is having problems removing an adapter. In some cases they can get it off without problems, in others, they have to disassemble the camera mount). But on the other hand, most people use unbranded adapters just fine, with no problem at all.
Thanks. Yeah, i found this on amazon. I've seen threads about problems with adapters, so am a bit affraid to buy them, except if original pentax. And about that tool - I thought straight away that this is strange, because that adapter that i have on the lens, can be screwed on just as easy as putting any other lens on.
And in the end of all, i think that the problem actually is in quality of the Optomax lens itself, cause i tried it in daylight, it kind of focused, but IQ is pretty bad, especially if you try to zoom in to the picture. Everything is grainy. I saw something similar on pictures of other people on flickr. Actually i get better image while using my KAX MC7 2x teleconverter.
And another thing, maybe you know... On this lens, under apperture ring is another ring with signs 0 and C. When you turn it, apperture closes to minimal value, but only if apperture ring itself was put on widest. Do you know what it is? Never seen anything like this... thanks.
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