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06-14-2017, 10:56 AM   #1
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Some questions about buying sony full frame + adapters + pentax full frame lens

Hi,

I am considering buy a sony full frame, a7, for example, as I heard it has better auto focus system.

I have a few questions, does pentax to sony adapter support full frame? How about the auto focus speed and accuracy compare with pentax k1 + pentax dfa / fa lens?

Thank you.

06-14-2017, 11:04 AM   #2
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I assume you are talking about the Techart Leica M Autofocus Adapter. (No other adapter will autofocus a K-mount lens).

Techart PRO Leica M – Sony E Autofocus Adapter | TECHART PRO

It seems to function the same way the Pentax F 1.7x AF adapter works...it moves the whole lens to focus.

Keep in mind that it will drain the already limited battery of the A7 (even when turned off)...

The whole thing is kind of a kludge. If you want to use K-mount lenses invest in a K-mount camera, unless you want to invest in E-mount lenses to get good AF performance.
06-14-2017, 11:55 AM   #3
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QuoteOriginally posted by jhlxxx Quote
Hi,

I am considering buy a sony full frame, a7, for example, as I heard it has better auto focus system.
It depends of which A7 you're thinking of and which lens at what aperture. The A7RII with a fast prime in can be really good, while the original A7 with a slow zoom isn't a match for any modern DSLR...
06-14-2017, 12:06 PM   #4
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What are you taking pictures of that the Pentax k1 autofocus couldn't handle?

06-14-2017, 02:26 PM - 1 Like   #5
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Don't buy a Sony camera unless you're seriously interested in the Sony system as a whole and have weighed all brands of DSLR plus all non-full-frame mirrorless in the balance and found them wanting for everything you intend to do.

Sony's strength with other people's lenses is strictly in the manual focus arena.

If you are buried under piles of ancient but still excellent or classical secondhand lenses from all sorts of makers and want to use them all, THAT is when you buy a Sony camera to use other people's lenses on. If you want to shoot Pentax AF lenses, get a Pentax AF camera. Otherwise you are crippling yourself.

Remember too that Sony's flash system and hotshoe fit-out is proprietary (a hangover from the dying days of Minolta) and does not play well with others. They are like the Apple Mac of cameras.

It goes deeper than the camera. Think carefully. Try before you buy. Borrow or rent if you can, and wring out the camera for all its defects and downsides. Then and only then make your purchase.
06-14-2017, 05:01 PM   #6
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QuoteOriginally posted by jhlxxx Quote
does pentax to sony adapter support full frame? How about the auto focus speed and accuracy compare with pentax k1 + pentax dfa / fa lens?
Every K-mount to E-mount adapter I've seen supports full-frame, even the $5 cheap ones from eBay.

AF speed and accuracy of Pentax K-1 and DFA/FA lenses will generally perform better with K-1 than A7 + E-mount lenses, and certainly K-1 + DFA/FA lenses will have better AF than A7 + Pentax lenses via an adapter (where AF will not work at all).

But it all depends on what your shooting subject is, with what lenses etc. Choose the features that are important to your requirements.

I like the face detection of Sony cameras, for instance, so that's a big plus when shooting people. But the low-light AF of most Sony's (including the A7) sucks - K-1 will autofocus down to [very dark] -3EV for instance, but A7 autofocus only functions reliably while the light remains pretty good [merely down to 0EV].

Note also that the AF of the A7 isn't as full-featured (and fast) as some of the newer Sony's. A7 is old tech.
06-14-2017, 05:08 PM   #7
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The A7 has focus technology too old and slow for that TechArt Pro adapter.
06-14-2017, 05:13 PM - 1 Like   #8
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QuoteOriginally posted by clackers Quote
The A7 has focus technology too old and slow for that TechArt Pro adapter.
Well. Yeah. It only works with the A7 II/ A7R II, A6300/6500 & A9...

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