Backfocus or Worse? at DVinfo.net

Steve Nettleton · April 9th, 2004, 03:37 AM

In the middle of a big shoot in India and suddenly my PD190 (same as PD170, but made in Shanghai) is giving me trouble. Extreme close-ups, with zoom all the way in, show a slight blur. You can see a fuzzy outline (often of white or blue) around the subject. Can't improve the focus with the focus ring. Is this a backfocus problem, or something else?

I've tested this with various settings, with ND filters on and off, with the wide angle lens on and off, with the UV filter on and off. It's worse when I shoot with ND-2 and the wide angle attached, but while it's less horrific with all filters and wide angles off, it still doesn't go away.

I'm in a place where there's no support for this kind of equipment, so any fixes are going to have to be done by myself, manually. Anyone have any suggestions? Thanks.

Mike Rehmus · April 9th, 2004, 03:48 PM

I'm not certain what you mean by zoom all the way in. If you mean at full-telphoto, the camera will not focus close-in at that setting. You have to use a wider field of view in order to get within even a few feet.

If you mean that you have the zoom set on the widest field of view and the lens will not focus, yes it may be a back-focus adjustment and will require a trip to a repair center.

Steve Nettleton · April 10th, 2004, 08:37 AM

Under what conditions can't you focus at the full telephoto focal length? Only with the wide angle on? Is this something peculiar to this camera? I used a w/a with the TRV950 without this same result. It's weird... not only fuzzy but almost like you're looking at two color separations overlapping but slightly offset. Like you're looking at something on the edge of the mirror where the colors don't sync. I use this for news production and I can't always swap the lens but I figured you could still zoom all the way in, but with the wide angle the focal length would be reduced by a factor of 0.7.

Mike Rehmus · April 10th, 2004, 11:14 AM

Under all conditions. The lens setup simply does not allow close focusing at the telephoto end of its range. I suppose a plus diopter close-up lens would help but at 58mm, it is going to be expensive and a PITR to take on and off.

Richard Iredale · April 10th, 2004, 10:38 PM

I think a "backfocus" issue refers to a situation where you zoom in, manually focus on the subject, and then notice that when you zoom out the subject is out of focus.

Wayne Orr · April 12th, 2004, 02:12 PM

Mike says "Under all conditions. The lens setup simply does not allow close focusing at the telephoto end of its range."

Huh? Do you mean less than three feet or so? Certainly you don't mean that as a blanket statement, do you Mike?

To Steve. Have you tried the "reset" button? It is located behind the lcd, in the lower right corner of all the menu buttons. A tiny button that needs a pin or ballpoint pen to press. This will restore your camera to factory defaults. You will need to reset your clock, etc, as though it were a brand new camera.

If that doesn't work, you could have a serious problem. But not back focus.

Wayne Orr, SOC

Mike Rehmus · April 12th, 2004, 07:48 PM

Mike says "Under all conditions. The lens setup simply does not allow close focusing at the telephoto end of its range."

Huh? Do you mean less than three feet or so? Certainly you don't mean that as a blanket statement, do you Mike?

You bet I do, Don. I've used the 150 in a lot of close (under 3 feet) situations and it is incapable of focusing close from about mid-way in the zoom range on in. Try it. Just focus on something about 2 feet away when the lens is fully wide. Then zoom in. The image will go out of focus and there is nothing you can do other than put a diopter or two on the lens to get it to focus.

Unless I have received 3 bad cameras, I do believe it is normal. I've had my hands on three of them for long durations.

Come to think of it, my old Sony Hi-8 exhibited the same focus capabilities.

And my pro lens as well. To focus close when zoomed in, I have to adjust the Macro ring.

With most pro video lenses, minimum distance is 1 meter. 'Close' focus lenses are good to about 10 cm without use of the Macro ring.

Wayne Orr · April 12th, 2004, 08:16 PM

Hi Mike. It's Wayne, here, who made that comment. The way your original post reads, it sounds like the camera will not focus at full telephoto, in any situation, which is why I said "less than three feet." I couldn't believe you were saying you can't focus at...twenty feet. I know what you meant (I think) but I was afraid it might confuse the original poster. Maybe I am the only one who was confused. Would't be the first time.

Wayne

Steve Nettleton · April 13th, 2004, 08:31 AM

I'm a little unclear about this. What I'm talking about is using the wide angle on a shoot, and realizing I need to go full telephoto on something 100 feet away. No time to change lenses. Just zoom and focus. But the focus is off, blurry, as I described above. Are you saying you can't focus using the wide angle on something at infinity?

Ken Plotin · April 13th, 2004, 09:46 AM

Steve,
This sounds more like extreme chromatic abberation than any back focus problem. The "double image at the edge" sounds like a lens element is mis-aligned or slightly shifted out of parallel.
It doesn't take much of a hit on the right spot to cause damage.
Had the problem once on an old 12-120 Angenieux zoom lens for 16mm. It was bounced around by the airline baggage folks who wouldn't allow the case as a carry on.
The resulting image on film was exactly what you describe.

Try shooting at full telephoto with the lens stopped down to 5.6 or 8 and see if you get a slight improvement. It's worse wide open (with your ND's) because you're seeing more of the flare caused by the mis alignment.
I don't think this is something you can repair yourself.

Ken

Wayne Orr · April 13th, 2004, 10:00 AM

OK, Steve, I gotcha. You are using a Sony wide angle adapter that came with your camera, right? When you zoom full tite at a subject in the distance, and attempt to focus, you get this blur effect. You see the same effect when you remove the lens, although maybe less. You are correct, that this is not normal. I strongly advise you to try the reset button. If this does not clear up the situation, I believe you have a problem that requires service. Hopefully you are still under warranty.

BTW, the Sony wide angle adapter is what is called a "zoom through," and will give you a sharp image throughout the zoom range. It is possible it may be sllightly soft at full tight, so I recommend you check for your problem without the lens attached.

HTH

Wayne

April 9th, 2004, 03:37 AM	#1
Steve Nettleton Regular Crew Join Date: Feb 2004 Location: Beijing, China Posts: 30	Backfocus or Worse? In the middle of a big shoot in India and suddenly my PD190 (same as PD170, but made in Shanghai) is giving me trouble. Extreme close-ups, with zoom all the way in, show a slight blur. You can see a fuzzy outline (often of white or blue) around the subject. Can't improve the focus with the focus ring. Is this a backfocus problem, or something else? I've tested this with various settings, with ND filters on and off, with the wide angle lens on and off, with the UV filter on and off. It's worse when I shoot with ND-2 and the wide angle attached, but while it's less horrific with all filters and wide angles off, it still doesn't go away. I'm in a place where there's no support for this kind of equipment, so any fixes are going to have to be done by myself, manually. Anyone have any suggestions? Thanks.

April 9th, 2004, 03:48 PM	#2
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	I'm not certain what you mean by zoom all the way in. If you mean at full-telphoto, the camera will not focus close-in at that setting. You have to use a wider field of view in order to get within even a few feet. If you mean that you have the zoom set on the widest field of view and the lens will not focus, yes it may be a back-focus adjustment and will require a trip to a repair center. __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

April 10th, 2004, 11:14 AM	#4
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	Under all conditions. The lens setup simply does not allow close focusing at the telephoto end of its range. I suppose a plus diopter close-up lens would help but at 58mm, it is going to be expensive and a PITR to take on and off. __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

April 12th, 2004, 07:48 PM	#7
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	Mike says "Under all conditions. The lens setup simply does not allow close focusing at the telephoto end of its range." Huh? Do you mean less than three feet or so? Certainly you don't mean that as a blanket statement, do you Mike? You bet I do, Don. I've used the 150 in a lot of close (under 3 feet) situations and it is incapable of focusing close from about mid-way in the zoom range on in. Try it. Just focus on something about 2 feet away when the lens is fully wide. Then zoom in. The image will go out of focus and there is nothing you can do other than put a diopter or two on the lens to get it to focus. Unless I have received 3 bad cameras, I do believe it is normal. I've had my hands on three of them for long durations. Come to think of it, my old Sony Hi-8 exhibited the same focus capabilities. And my pro lens as well. To focus close when zoomed in, I have to adjust the Macro ring. With most pro video lenses, minimum distance is 1 meter. 'Close' focus lenses are good to about 10 cm without use of the Macro ring. __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

April 10th, 2004, 08:37 AM	#3
Steve Nettleton Regular Crew Join Date: Feb 2004 Location: Beijing, China Posts: 30	Under what conditions can't you focus at the full telephoto focal length? Only with the wide angle on? Is this something peculiar to this camera? I used a w/a with the TRV950 without this same result. It's weird... not only fuzzy but almost like you're looking at two color separations overlapping but slightly offset. Like you're looking at something on the edge of the mirror where the colors don't sync. I use this for news production and I can't always swap the lens but I figured you could still zoom all the way in, but with the wide angle the focal length would be reduced by a factor of 0.7.

April 10th, 2004, 10:38 PM	#5
Richard Iredale Regular Crew Join Date: Dec 2003 Location: Portland, OR Posts: 67	I think a "backfocus" issue refers to a situation where you zoom in, manually focus on the subject, and then notice that when you zoom out the subject is out of focus.

April 12th, 2004, 02:12 PM	#6
Wayne Orr Major Player Join Date: Dec 2002 Location: Northridge Ca Posts: 734	Mike says "Under all conditions. The lens setup simply does not allow close focusing at the telephoto end of its range." Huh? Do you mean less than three feet or so? Certainly you don't mean that as a blanket statement, do you Mike? To Steve. Have you tried the "reset" button? It is located behind the lcd, in the lower right corner of all the menu buttons. A tiny button that needs a pin or ballpoint pen to press. This will restore your camera to factory defaults. You will need to reset your clock, etc, as though it were a brand new camera. If that doesn't work, you could have a serious problem. But not back focus. Wayne Orr, SOC

April 12th, 2004, 08:16 PM	#8
Wayne Orr Major Player Join Date: Dec 2002 Location: Northridge Ca Posts: 734	Hi Mike. It's Wayne, here, who made that comment. The way your original post reads, it sounds like the camera will not focus at full telephoto, in any situation, which is why I said "less than three feet." I couldn't believe you were saying you can't focus at...twenty feet. I know what you meant (I think) but I was afraid it might confuse the original poster. Maybe I am the only one who was confused. Would't be the first time. Wayne

April 13th, 2004, 08:31 AM	#9
Steve Nettleton Regular Crew Join Date: Feb 2004 Location: Beijing, China Posts: 30	I'm a little unclear about this. What I'm talking about is using the wide angle on a shoot, and realizing I need to go full telephoto on something 100 feet away. No time to change lenses. Just zoom and focus. But the focus is off, blurry, as I described above. Are you saying you can't focus using the wide angle on something at infinity?

April 13th, 2004, 09:46 AM	#10
Ken Plotin Major Player Join Date: Jan 2004 Location: Los Angeles, CA Posts: 254	Steve, This sounds more like extreme chromatic abberation than any back focus problem. The "double image at the edge" sounds like a lens element is mis-aligned or slightly shifted out of parallel. It doesn't take much of a hit on the right spot to cause damage. Had the problem once on an old 12-120 Angenieux zoom lens for 16mm. It was bounced around by the airline baggage folks who wouldn't allow the case as a carry on. The resulting image on film was exactly what you describe. Try shooting at full telephoto with the lens stopped down to 5.6 or 8 and see if you get a slight improvement. It's worse wide open (with your ND's) because you're seeing more of the flare caused by the mis alignment. I don't think this is something you can repair yourself. Ken

April 13th, 2004, 10:00 AM	#11
Wayne Orr Major Player Join Date: Dec 2002 Location: Northridge Ca Posts: 734	OK, Steve, I gotcha. You are using a Sony wide angle adapter that came with your camera, right? When you zoom full tite at a subject in the distance, and attempt to focus, you get this blur effect. You see the same effect when you remove the lens, although maybe less. You are correct, that this is not normal. I strongly advise you to try the reset button. If this does not clear up the situation, I believe you have a problem that requires service. Hopefully you are still under warranty. BTW, the Sony wide angle adapter is what is called a "zoom through," and will give you a sharp image throughout the zoom range. It is possible it may be sllightly soft at full tight, so I recommend you check for your problem without the lens attached. HTH Wayne