Focus problems at DVinfo.net

Samuel Birkan · November 22nd, 2004, 07:36 AM

Correct me if I am mistaken, but if I zoom in to a subject, then focus manually and then zoom out, should the subject not remain in focus ?. Mine loses focus completely. I have also noticed that when manually focusing the distance shown in the display is much closer than the real distance ( I do know metric distances). The autofocus also seems to be very slow.

Boyd Ostroff · November 22nd, 2004, 10:18 AM

Hi Samuel,

It is possible that this could be a defect in your camera if I understand you correctly. When you say it "loses focus completely," does that mean everything turns into a "blob," or just that it doesn't look as sharp as you'd like? Wide shots on the PDX-10, and most inexpensive DV cameras, leave a lot to be desired. This is not really a defect, but just a design limitation. I don't see a problem like you describe with my camera, although I am often disappointed with the overall softness of wide shots, no matter how hard I try to focus them. I also find it can be very sensitive to exposure. You may need to adjust exposure as you zoom since the lens is a stop or two slower at the telephoto end of its range.

The reality is that when you zoom all the way out a camera with tiny chips like the PDX-10 has a vast depth of field, and the focus is not particularly critical. Now I personally am very skeptical about those "distances" displayed in the viewfinder. But I find the autofocus pretty responsive; it acts just about the same as my VX-2000 and people have long said that was better than the XL-1s for example. In low light/low contrast situations you will have some problems, but I think that's to be expected.

Maybe someone with better technical knowledge can help here, but I think that autofocus works using contrast calculations, and is not really related to distance at all. If you have an NLE or some other software that can display a waveform graph in realtime over firewire, try plugging in your camera and racking the focus as you watch the display (I use BTV Pro for this sometimes). Now turn on autofocus and observe. This will give you an idea of how autofocus works (if I correctly understand things :-). Unfortunately, I think there are some things which can fool this system. For example, you may not want to focus on the highest contrast part of the image.

Now I do have a pet peeve about focus on my PDX-10 and am surprised that nobody else has mentioned it. Maybe I'm just being picky, or maybe my camera has always had a defect also? When I zoom all the way in to the max either with or without autofocus, there is a brief moment where the image goes soft at the very end of the zoom when it completes. As soon as I release the rocker (or my LANC controller) the image snaps back into sharp focus. Actually it is less noticeable when zooming IN, but more annoying just as you begin to zoom OUT from full telephoto. Now this is just a very brief transient glitch, but I find it disconcerting. Turning on autofocus seems to help with this just a bit, but does not eliminate the problem. Turning steadyshot on or off has no effect on the problem. My workaround has been to try and stop just short of full zoom whenever possible. I am not a big fan of zooming anyway, but when shooting performances it's impossible to avoid...

Samuel Birkan · November 22nd, 2004, 10:40 AM

Thanks for your reply. . I was not trying to zoom while filming but zoom in, focus then, zoom out to frame the shot.
The focus loss after the zoom out is complete, not just not sharp, but completely fuzzy over the whole depth of the frame. The focus button is on manual all the time
I tried to talk to Sony tech support but the person I got did not have the slightest idea what I was talking about. Then I tried online chat and the only sugestion was to reset the camera ????

Samuel Birkan · November 22nd, 2004, 02:12 PM

I am getting conflicting answers from different sources.
Would someone with a TRV950 or PDX10 mind testing this on their camera and post the results. I would hate to send the camera in for repair then find out that that's how it works.
Thanks for your help.

Boyd Ostroff · November 22nd, 2004, 04:46 PM

Samuel, I understand what you're saying. If I zoom in all the way to max telephoto, focus on something, then zoom all the way out to wide then my camera does NOT lose focus as you describe. I think the technical term for what you have is a "backfocus problem."

Did you try resetting the camera? No idea whether this would help but I suppose there's no harm trying. The button is recessed next to the zebra switch. I've never had to deal with Sony's repair service so I can't help there, sorry. Be sure you're talking to the broadcast/professional division instead of the consumer part. That's one of the advantages to the PDX-10, and I have read a number of good reports about their service and turnaround time. I think this web page will give you contact info http://bssc.sel.sony.com/Professiona...cecenters.html

Steve Tapping · November 22nd, 2004, 10:31 PM

Boyd I have the same problem, when zooming out/in just before full telephoto the image goes soft. Alot of my work uses full telephoto & sometimes I am forced to zoom in or out while shooting. This softness is unacceceptable. Personally it is the biggest downfall I have found with this camera, the average audience could identify this as being poorly shot.
Like you said the best way to avoid it is shooting before the lens reaches full optical zoom. I would say it forces it back to a 10x zoom, an interesting thing to test would be to allow 24x digital zoom & see if it still does it at the 12x mark. I currently don't have my PDX10 so could you test this please Boyd. I don't think it will make a difference but worth a try.

Samuel Birkan · November 24th, 2004, 07:59 AM

I tried a few things yesterday afternoon. I had noticed the problem on an indoor event with very bad lighting (most of what I had to shoot had strong backlight)
I tried it outside on a grey day and found the problem only seems to happen when the zoom changes lighting conditions drasticley. (eg : starts inside finishes outside). I also reset the camera , I noticed that after the reset the reported distances on manual focus seemed to be more accurate.
So I am concluding that it is not a lens problem.

November 22nd, 2004, 07:36 AM	#1
Samuel Birkan Regular Crew Join Date: Sep 2004 Location: Cincinnati Ohio Posts: 79	Focus problems Correct me if I am mistaken, but if I zoom in to a subject, then focus manually and then zoom out, should the subject not remain in focus ?. Mine loses focus completely. I have also noticed that when manually focusing the distance shown in the display is much closer than the real distance ( I do know metric distances). The autofocus also seems to be very slow.

November 22nd, 2004, 10:18 AM	#2
Boyd Ostroff Wrangler Join Date: Dec 2002 Location: Mays Landing, NJ Posts: 11,802	Hi Samuel, It is possible that this could be a defect in your camera if I understand you correctly. When you say it "loses focus completely," does that mean everything turns into a "blob," or just that it doesn't look as sharp as you'd like? Wide shots on the PDX-10, and most inexpensive DV cameras, leave a lot to be desired. This is not really a defect, but just a design limitation. I don't see a problem like you describe with my camera, although I am often disappointed with the overall softness of wide shots, no matter how hard I try to focus them. I also find it can be very sensitive to exposure. You may need to adjust exposure as you zoom since the lens is a stop or two slower at the telephoto end of its range. The reality is that when you zoom all the way out a camera with tiny chips like the PDX-10 has a vast depth of field, and the focus is not particularly critical. Now I personally am very skeptical about those "distances" displayed in the viewfinder. But I find the autofocus pretty responsive; it acts just about the same as my VX-2000 and people have long said that was better than the XL-1s for example. In low light/low contrast situations you will have some problems, but I think that's to be expected. Maybe someone with better technical knowledge can help here, but I think that autofocus works using contrast calculations, and is not really related to distance at all. If you have an NLE or some other software that can display a waveform graph in realtime over firewire, try plugging in your camera and racking the focus as you watch the display (I use BTV Pro for this sometimes). Now turn on autofocus and observe. This will give you an idea of how autofocus works (if I correctly understand things :-). Unfortunately, I think there are some things which can fool this system. For example, you may not want to focus on the highest contrast part of the image. Now I do have a pet peeve about focus on my PDX-10 and am surprised that nobody else has mentioned it. Maybe I'm just being picky, or maybe my camera has always had a defect also? When I zoom all the way in to the max either with or without autofocus, there is a brief moment where the image goes soft at the very end of the zoom when it completes. As soon as I release the rocker (or my LANC controller) the image snaps back into sharp focus. Actually it is less noticeable when zooming IN, but more annoying just as you begin to zoom OUT from full telephoto. Now this is just a very brief transient glitch, but I find it disconcerting. Turning on autofocus seems to help with this just a bit, but does not eliminate the problem. Turning steadyshot on or off has no effect on the problem. My workaround has been to try and stop just short of full zoom whenever possible. I am not a big fan of zooming anyway, but when shooting performances it's impossible to avoid...

November 22nd, 2004, 10:40 AM	#3
Samuel Birkan Regular Crew Join Date: Sep 2004 Location: Cincinnati Ohio Posts: 79	Thanks for your reply. . I was not trying to zoom while filming but zoom in, focus then, zoom out to frame the shot. The focus loss after the zoom out is complete, not just not sharp, but completely fuzzy over the whole depth of the frame. The focus button is on manual all the time I tried to talk to Sony tech support but the person I got did not have the slightest idea what I was talking about. Then I tried online chat and the only sugestion was to reset the camera ????

November 22nd, 2004, 02:12 PM	#4
Samuel Birkan Regular Crew Join Date: Sep 2004 Location: Cincinnati Ohio Posts: 79	I am getting conflicting answers from different sources. Would someone with a TRV950 or PDX10 mind testing this on their camera and post the results. I would hate to send the camera in for repair then find out that that's how it works. Thanks for your help.

November 22nd, 2004, 04:46 PM	#5
Boyd Ostroff Wrangler Join Date: Dec 2002 Location: Mays Landing, NJ Posts: 11,802	Samuel, I understand what you're saying. If I zoom in all the way to max telephoto, focus on something, then zoom all the way out to wide then my camera does NOT lose focus as you describe. I think the technical term for what you have is a "backfocus problem." Did you try resetting the camera? No idea whether this would help but I suppose there's no harm trying. The button is recessed next to the zebra switch. I've never had to deal with Sony's repair service so I can't help there, sorry. Be sure you're talking to the broadcast/professional division instead of the consumer part. That's one of the advantages to the PDX-10, and I have read a number of good reports about their service and turnaround time. I think this web page will give you contact info http://bssc.sel.sony.com/Professiona...cecenters.html

November 22nd, 2004, 10:31 PM	#6
Steve Tapping Regular Crew Join Date: Oct 2003 Location: Australia WA Posts: 41	Boyd I have the same problem, when zooming out/in just before full telephoto the image goes soft. Alot of my work uses full telephoto & sometimes I am forced to zoom in or out while shooting. This softness is unacceceptable. Personally it is the biggest downfall I have found with this camera, the average audience could identify this as being poorly shot. Like you said the best way to avoid it is shooting before the lens reaches full optical zoom. I would say it forces it back to a 10x zoom, an interesting thing to test would be to allow 24x digital zoom & see if it still does it at the 12x mark. I currently don't have my PDX10 so could you test this please Boyd. I don't think it will make a difference but worth a try.

November 24th, 2004, 07:59 AM	#7
Samuel Birkan Regular Crew Join Date: Sep 2004 Location: Cincinnati Ohio Posts: 79	I tried a few things yesterday afternoon. I had noticed the problem on an indoor event with very bad lighting (most of what I had to shoot had strong backlight) I tried it outside on a grey day and found the problem only seems to happen when the zoom changes lighting conditions drasticley. (eg : starts inside finishes outside). I also reset the camera , I noticed that after the reset the reported distances on manual focus seemed to be more accurate. So I am concluding that it is not a lens problem.