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10-28-2010, 04:29 PM   #16
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QuoteOriginally posted by clark Quote
thanks
the gh1 senses when you're manually focussing and automatically zooms in, i'm 80% sure it still does this even when you're mounting an adapted lens
The gh1 uses fly-by-wire to manually zoom. You don't directly turn the focus wheel. Rather, you send focus commands to the camera body which then activates the focus motor.

I prefer (by a large amount) the sublime and direct feel of a well-made manual focus lens like a Zeiss or Pentax FA Limited. IMHO, to give up that feeling is a price to high to pay for autozoom. But as I said, the camera could still do it by observing the change in contrast.

10-29-2010, 06:49 AM   #17
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QuoteOriginally posted by falconeye Quote
The gh1 uses fly-by-wire to manually zoom. You don't directly turn the focus wheel. Rather, you send focus commands to the camera body which then activates the focus motor.

I prefer (by a large amount) the sublime and direct feel of a well-made manual focus lens like a Zeiss or Pentax FA Limited. IMHO, to give up that feeling is a price to high to pay for autozoom. But as I said, the camera could still do it by observing the change in contrast.

right, ok, thanks for clearing that up
The guys at the camera shop seemed to think it would, but what do they know
10-29-2010, 06:44 PM   #18
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QuoteOriginally posted by falconeye Quote
IMHO, to give up that feeling is a price to high to pay for autozoom.
Clearly MF lenses are out of the question but isn't it the case that AF lenses have some feedback mechanism that gives the body at least a rough idea where the focus is? I've seen opto-mechanical constructions and one user who's FA 50/1.4 fell apart speaks of "focus position contact brushes". In other words, some AF lenses may actually be able to tell the body that their focus position has been changed.

Last edited by Class A; 10-30-2010 at 04:52 AM.
10-29-2010, 06:53 PM   #19
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QuoteOriginally posted by clark Quote
thanks
fwiw (i'm sure you know this but...)the gh1 senses when you're manually focussing and automatically zooms in, i'm 80% sure it still does this even when you're mounting an adapted lens
I've had a panny GF1 and now the olympus e-pl1 - I find the auto zoom feature a pain to be honest. Any little bump of the focus ring activates it (of course you can turn it off, but when you actually want to use it, it is handy). the AF in liveview is a big leap from the kx and k7, I am really impressed in my short time with it so far!

10-30-2010, 04:25 AM   #20
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QuoteOriginally posted by Class A Quote
isn't it the case that AF lenses have some feedback mechanism
I would be glad to learn about. With Pentax, the EXIF contains info like "macro", "near" or "far distance", I believe. I always thought it comes from the AF algorithm, have to check EXIF with manual focussing an FA lens...

But at least with Pentax, the feedback isn't with that Ám precision you would need for focus-by-wire or to notice minimal changes of the focus position.

So, the Pentax lenses may have focus position contact brushes but I fear, not enough of them to reliably detect a turn of the focus wheel.

However as I said, I would be glad to learn more about this topic.
10-30-2010, 05:05 AM   #21
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QuoteOriginally posted by falconeye Quote
If you're really curious to know what's going on in LV, I recommend doing one of my standard tests.
Have you ever tried with HDMI to a full HD TV? I wonder to if the screen from K-5 is the same as the K-7? And if the limitation is coming from the backscreen or from the output that the camera is delivering.
10-30-2010, 01:38 PM   #22
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QuoteOriginally posted by falconeye Quote
But at least with Pentax, the feedback isn't with that Ám precision you would need for focus-by-wire or to notice minimal changes of the focus position.
Yes, you are probably right. A brush type arrangement will provide only quite coarse info.

I seem to remember to have seen an photoelectrical design like this one:

but all my search efforts didn't unearth the image of the disassembled lens I have in my mind.
10-30-2010, 01:48 PM   #23
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Looks to be the original by John Logie Baird

10-30-2010, 03:53 PM   #24
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QuoteOriginally posted by Class A Quote
I seem to remember to have seen an photoelectrical design like this one:
Thanks for the image. It's what the e-dials look like (smaller wheel with fewer holes). Mechanical computer mice worked like this too. This kind of design transmits no absolute position data though and wouldn't collect more data than the body already knows due to screw drive rotations.

A design with brushes would probably be different though as you would have far less brushes w/o a PCB to wire them all.
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