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09-12-2011, 04:25 AM   #1
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[langtitle=fr]Adaptation objectif sigma sur pentax kx[/langtitle]

Salut tout le Monde,

j'ai un sony alpha 100 et je viens d'acheter un Pentax Kx, sur le quel j'aimerais adapter les objectifs de mon autre reflex. Les objectifs du Sony sont de marque Sigma. On m'as dis qu'il existe des bagues d'adaptation. Est-ce vrais? Savez vous la reference exacte et le prix un peu pres? Et ou puis-je trouver ca?
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Last edited by captaindeejay; 09-12-2011 at 04:27 AM. Reason: Objectif Sigma sur Pentax kx
09-12-2011, 04:47 AM   #2
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Hello,

Sorry, I don't know for certain but I have a feeling that these don't exist - see here.
09-12-2011, 11:02 AM   #3
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I just searched eBay for SONY ALPHA PENTAX ADAPT* -M42 and found no A-PK adapters at all. If such did exist, they would either be optical, which lowers IQ, or non-infinity-focus, for closeups only. PK lenses can be adapted to Minolta-Sony-Alpha mount, but not vice-versa except with major surgery. (That's why I sold off my Alpha stuff.)
09-12-2011, 12:05 PM   #4
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I'm not entirely sure what you're trying to ask, but I'll take a stab at it—you don't need an adapter for Sigma lenses for Pentax, provided that they are in the Pentax mount. In other words, Sigma makes lenses for Pentax as well as sony. However, the mounts are different.

That may be irrelevant. But at least I tried.

09-12-2011, 01:22 PM   #5
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QuoteOriginally posted by Ubuntu_user Quote
I'm not entirely sure what you're trying to ask, but I'll take a stab at it—you don't need an adapter for Sigma lenses for Pentax, provided that they are in the Pentax mount. In other words, Sigma makes lenses for Pentax as well as sony. However, the mounts are different.
I think the question was: The OP has Sigma lenses in Sony-Minolta Alpha mount; can they be adapted to Pentax mount? And the answer is no, not without major surgery and loss of autofocus. Going the other way, fitting PK lenses on the Alpha mount, *IS* possible, but only with loss of IQ or infinity focus.
09-12-2011, 03:39 PM   #6
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QuoteOriginally posted by RioRico Quote
I think the question was: The OP has Sigma lenses in Sony-Minolta Alpha mount; can they be adapted to Pentax mount? And the answer is no, not without major surgery and loss of autofocus. Going the other way, fitting PK lenses on the Alpha mount, *IS* possible, but only with loss of IQ or infinity focus.
Oh, I didn't think that adapting PK lenses to the alpha mount was that bad... I just read not long ago about somebody here that adapted their A 50mm f/1.2 to Alpha mount and ran it on their A900 FF camera.
09-12-2011, 04:19 PM   #7
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QuoteOriginally posted by Ubuntu_user Quote
Oh, I didn't think that adapting PK lenses to the alpha mount was that bad... I just read not long ago about somebody here that adapted their A 50mm f/1.2 to Alpha mount and ran it on their A900 FF camera.
Going PK-->Alpha isn't a real problem. Going Alpha-->PK *is* a problem, and that's the OP's dilemma. The hangups are throat size, and register. Long-register lenses can (theoretically) be fitted to short-register cameras and retain infinity focus, but not the other way around.

Registers: Nikon= 46.5mm - Pentax= 45.46mm - Alpha= 44.5mm

It's no big deal for me to force-fit a Nikon lens to a Pentax mount; their bayonets are nearly identical, with lens throats of 44mm diameter. It focuses slightly past infinity. But a Pentax lens on a Nikon camera either won't focus to infinity, or needs an optical adapter that acts as a short TC and reduces IQ a bit. An Alpha lens on a Pentax camera has the same problem.

The Alpha bayonet is a different size, with lens throat of 49.7mm diameter, which is wider than the entire Pentax or Nikon bayonet. A Pentax or Nikon lens could have its base removed and replaced with with an Alpha base (and no AF, of course.) But not vice-versa. With MAJOR surgery, well maybe, but probably not. So even without the register disparity, the Alpha lens just won't squeeze down the Pentax throat.

Last edited by RioRico; 09-12-2011 at 04:27 PM.
09-12-2011, 07:47 PM   #8
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QuoteOriginally posted by RioRico Quote
Going PK-->Alpha isn't a real problem. Going Alpha-->PK *is* a problem, and that's the OP's dilemma. The hangups are throat size, and register. Long-register lenses can (theoretically) be fitted to short-register cameras and retain infinity focus, but not the other way around.

Registers: Nikon= 46.5mm - Pentax= 45.46mm - Alpha= 44.5mm

It's no big deal for me to force-fit a Nikon lens to a Pentax mount; their bayonets are nearly identical, with lens throats of 44mm diameter. It focuses slightly past infinity. But a Pentax lens on a Nikon camera either won't focus to infinity, or needs an optical adapter that acts as a short TC and reduces IQ a bit. An Alpha lens on a Pentax camera has the same problem.

The Alpha bayonet is a different size, with lens throat of 49.7mm diameter, which is wider than the entire Pentax or Nikon bayonet. A Pentax or Nikon lens could have its base removed and replaced with with an Alpha base (and no AF, of course.) But not vice-versa. With MAJOR surgery, well maybe, but probably not. So even without the register disparity, the Alpha lens just won't squeeze down the Pentax throat.
Interesting! Thanks for informing me...

09-12-2011, 10:29 PM   #9
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QuoteOriginally posted by Ubuntu_user Quote
Interesting! Thanks for informing me...
U-betcha! I'm always glad to share my ignorance.
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