Focus issue solved, faulty camera now replaced

Philip Williams · January 4th, 2007, 06:11 AM

Quote:

Originally Posted by Sergio Barbosa

<snip> Has anyone tried zooming manually with autofocus on... <snip>

Uh.. well, you don't really zoom "manually". Its always a servo controlled zoom, regardless of if you use the rocker or the lens ring. So if you zoom (using any method) with autofocus on, the pulsing can occur.

Michael Mann · January 4th, 2007, 01:39 PM

Quote:

Originally Posted by Philip Williams

So if you zoom (using any method) with autofocus on, the pulsing can occur.

Sounds reasonable. Anyway - has anyone TESTED whether the pulsing really occurs during "manual" zooms? Thanks, Sergio, for your proposal. I will test and report.

Quote:

Originally Posted by Alex Leigh

There have been occasions where I'd like to rack focus and zoom at the same time (background landscape to foreground presenter for example).

Yes, that goes for me too. And there is no possible workaround - either zoom or focus. (Not true: We could always focus in camera and "zoom" in post - I'm joking).
Thanks, Alex, for your "servo"-explanation. Again, the manual should at least inform about this quite fundamental "zoom OR focus"-limitation. (No reason for indignation, fans: I would have bought the A1 just the same. Like Alex says: The image quality in 25F is simply too good to resist).

Raymond Toussaint · January 4th, 2007, 06:34 PM

Quote:

Originally Posted by Raymond Toussaint

1. You can manually focus and zoom together.
1a.You can manually focus and zoom together and use Push Focus button on subject.

/snip

Normally always set everything on manual and use the push focus button if needed. Or if you want to use AF, not in the same time during the zoom, set cam to AF for easy focussing on moving object.

I need to come back on my early post on manually focus/zoom behavior, camera is back in the house and todays testing find out that you can not zoom and focus together. You can move the rings but one action (zoom) has priority over the other (focus). You can zoom in manually and push AF button but actually focussing is on the moment the zoom acton is finished.

Michael Mann · January 7th, 2007, 11:13 AM

Meanwhile I tested whether the AF focus pulsing also does occur while zooming manually (by zoom ring), as proposed by Sergio Barbosa. My first impression is that the pulsing is just the same.

Raymond Toussaint · January 7th, 2007, 06:56 PM

I tested it too, there is no focus pulsing. Only in badly lit, no contrast situations where an object is out of the center in the screen, and you zoom in, auto focus can't be easy found. This is understandable behavior, an object needs to stay in the middle, the two-way focus system tries one after one to focus, that is shifting in and out focus. It is very rare to happen, it is autofocus behavior. Sure you can manual focus in that situation.

Ben Hayflick · January 8th, 2007, 01:32 PM

Hi all, first time poster.

Reading through this thread it occurred to me, is the focus-pulse-during-zoom thing largely a PAL issue? An earlier poster touched on this but nobody seemed to pick up on it.

It just seemed to me that most (if not all) of the people who have complained of this problem seem to be from Europe and thus would be using the PAL version of the A1. Right? I haven't gone back through the entire thread systematically, but is it possible that the problem only exists on the PAL version, or is more pronounced on the PAL version?

Michael Mann · January 8th, 2007, 01:54 PM

Ben, yes, judging from the reactions so far the pulsing may possibly be more pronounced on PAL units. Tom Roper posted a short 24p clip (NTSC unit) that also showed the pulsing, but I found it less pronounced than the pulsing I get on my PAL A1. But to become more certain, we would need more reports.

Philip Williams · January 8th, 2007, 02:11 PM

The focus pulsing is probably due to the lower sampling rate of PAL shooting compared to NTSC shooting. When stepping down to 24F the sampling rate is very low, hence the pulsing appears on the NTSC model at that point.

FYI, I've shot some 24F under challenging lighting/focusing environments and gotten pretty severe pulsing, worse than Tom's sample.

Michael Mann · January 8th, 2007, 02:22 PM

Quote:

Originally Posted by Philip Williams

I've shot some 24F under challenging lighting/focusing environments and gotten pretty severe pulsing, worse than Tom's sample.

Philipp, if possible - could you upload a short sample of yours?

Alex Leith · January 9th, 2007, 04:15 AM

It's fairly likely that the pulsing is caused by the motor switching back and forth between focus and zoom.

If this is the case it could be possible that in 24F/25F we're seeing a temporal artefact.

For example, if this switching happens at 30 times a second (say) then you wouldn't see it in 30F or 60i.

But you would see it in 24F/25F and to a lesser degree in 50i (although the interlace scanning would somewhat cancel out the effect).

So it's possible it might be invisible to the vast majority of users who are filming 60i...

Michael Mann · January 9th, 2007, 04:56 AM

Interesting thought, Alex.
Could anyone of the NTSC users shoot and upload a short native demo take in 60i (slow zooming to the long end, AF switched on)?

Philip Williams · January 9th, 2007, 06:42 AM

I don't have upload capabilities here, otherwise I'd try to get a comparison 24F/60i clip up.

I can say that I actually tried to get the effect in 60i and wasn't able to.

Michael Mann · January 9th, 2007, 06:53 AM

Quote:

Originally Posted by Philip Williams

I don't have upload capabilities here, otherwise I'd try to get a comparison 24F/60i clip up. I can say that I actually tried to get the effect in 60i and wasn't able to.

Thanks, Philip. That is interesting to know even so.

Ben Hayflick · January 9th, 2007, 08:58 AM

So does the pulsing happen in NTSC at 30F?

Michael Mann · January 10th, 2007, 03:40 AM

Quote:

Originally Posted by Ben Hayflick

So does the pulsing happen in NTSC at 30F?

We simply don't know yet in general, Ben. Therefore we would need more reports from NTSC users.

January 7th, 2007, 11:13 AM	#109
Michael Mann Major Player Join Date: Dec 2005 Location: Kelkheim, Germany Posts: 375	Meanwhile I tested whether the AF focus pulsing also does occur while zooming manually (by zoom ring), as proposed by Sergio Barbosa. My first impression is that the pulsing is just the same. __________________ Michael

January 8th, 2007, 01:54 PM	#112
Michael Mann Major Player Join Date: Dec 2005 Location: Kelkheim, Germany Posts: 375	Ben, yes, judging from the reactions so far the pulsing may possibly be more pronounced on PAL units. Tom Roper posted a short 24p clip (NTSC unit) that also showed the pulsing, but I found it less pronounced than the pulsing I get on my PAL A1. But to become more certain, we would need more reports. __________________ Michael

January 8th, 2007, 02:11 PM	#113
Philip Williams Major Player Join Date: Aug 2004 Location: Snellville, Georgia Posts: 614	The focus pulsing is probably due to the lower sampling rate of PAL shooting compared to NTSC shooting. When stepping down to 24F the sampling rate is very low, hence the pulsing appears on the NTSC model at that point. FYI, I've shot some 24F under challenging lighting/focusing environments and gotten pretty severe pulsing, worse than Tom's sample. __________________ www.philipwilliams.com

January 9th, 2007, 04:15 AM	#115
Alex Leith Major Player Join Date: Mar 2005 Location: Northampton, England Posts: 500	It's fairly likely that the pulsing is caused by the motor switching back and forth between focus and zoom. If this is the case it could be possible that in 24F/25F we're seeing a temporal artefact. For example, if this switching happens at 30 times a second (say) then you wouldn't see it in 30F or 60i. But you would see it in 24F/25F and to a lesser degree in 50i (although the interlace scanning would somewhat cancel out the effect). So it's possible it might be invisible to the vast majority of users who are filming 60i... __________________ Alex

January 9th, 2007, 04:56 AM	#116
Michael Mann Major Player Join Date: Dec 2005 Location: Kelkheim, Germany Posts: 375	Interesting thought, Alex. Could anyone of the NTSC users shoot and upload a short native demo take in 60i (slow zooming to the long end, AF switched on)? __________________ Michael

January 7th, 2007, 06:56 PM	#110
Raymond Toussaint Regular Crew Join Date: Nov 2005 Posts: 173	I tested it too, there is no focus pulsing. Only in badly lit, no contrast situations where an object is out of the center in the screen, and you zoom in, auto focus can't be easy found. This is understandable behavior, an object needs to stay in the middle, the two-way focus system tries one after one to focus, that is shifting in and out focus. It is very rare to happen, it is autofocus behavior. Sure you can manual focus in that situation.

January 8th, 2007, 01:32 PM	#111
Ben Hayflick Regular Crew Join Date: Jan 2007 Location: NY, NY Posts: 55	Hi all, first time poster. Reading through this thread it occurred to me, is the focus-pulse-during-zoom thing largely a PAL issue? An earlier poster touched on this but nobody seemed to pick up on it. It just seemed to me that most (if not all) of the people who have complained of this problem seem to be from Europe and thus would be using the PAL version of the A1. Right? I haven't gone back through the entire thread systematically, but is it possible that the problem only exists on the PAL version, or is more pronounced on the PAL version?

January 9th, 2007, 06:42 AM	#117
Philip Williams Major Player Join Date: Aug 2004 Location: Snellville, Georgia Posts: 614	I don't have upload capabilities here, otherwise I'd try to get a comparison 24F/60i clip up. I can say that I actually tried to get the effect in 60i and wasn't able to. __________________ www.philipwilliams.com

January 9th, 2007, 08:58 AM	#119
Ben Hayflick Regular Crew Join Date: Jan 2007 Location: NY, NY Posts: 55	So does the pulsing happen in NTSC at 30F?