Question for K-5 owners: LV zoom-in quality?

falconeye · 10-28-2010, 04:29 PM

Originally posted by clark

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.

clark · 10-29-2010, 06:49 AM

Originally posted by falconeye

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

Class A · 10-29-2010, 06:44 PM

Originally posted by falconeye

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.

pxpaulx · 10-29-2010, 06:53 PM

Originally posted by clark

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!

falconeye · 10-30-2010, 04:25 AM

Originally posted by Class A

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 µm 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.

RonHendriks1966 · 10-30-2010, 05:05 AM

Originally posted by falconeye

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.

Class A · 10-30-2010, 01:38 PM

Originally posted by falconeye

But at least with Pentax, the feedback isn't with that µm 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.

Col · 10-30-2010, 01:48 PM

Looks to be the original by John Logie Baird

falconeye · 10-30-2010, 03:53 PM

Originally posted by Class A

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.

10-29-2010, 06:44 PM	#18
Class A Pentaxian Join Date: Aug 2008 Location: Wellington, New Zealand Posts: 11,251	Originally posted by falconeye 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.

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10-28-2010, 04:29 PM	#16
falconeye Veteran Member Join Date: Jan 2008 Location: Munich, Alps, Germany Photos: Gallery Posts: 6,871	Originally posted by clark 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
clark Inactive Account Join Date: Jun 2010 Posts: 301	Originally posted by falconeye 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, 06:53 PM	#19
pxpaulx Veteran Member Join Date: May 2009 Location: Twin Cities, MN Posts: 2,867	Originally posted by clark 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
falconeye Veteran Member Join Date: Jan 2008 Location: Munich, Alps, Germany Photos: Gallery Posts: 6,871	Originally posted by Class A 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 µm 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
RonHendriks1966 Banned Join Date: Jan 2009 Photos: Gallery Posts: 9,675	Originally posted by falconeye 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
Class A Pentaxian Join Date: Aug 2008 Location: Wellington, New Zealand Posts: 11,251	Originally posted by falconeye But at least with Pentax, the feedback isn't with that µm 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
Col Veteran Member Join Date: Apr 2007 Location: Stansted Essex Photos: Gallery Posts: 614	Looks to be the original by John Logie Baird

10-30-2010, 03:53 PM	#24
falconeye Veteran Member Join Date: Jan 2008 Location: Munich, Alps, Germany Photos: Gallery Posts: 6,871	Originally posted by Class A 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.