focusing while zooming at DVinfo.net

Vincent Im · January 23rd, 2004, 12:18 PM

How do you go about keeping focus on a subject while zooming in/out?

Do you have to use auto focus for this? How do you know auto focus won't be focusing on something else?

Are there accessories that allows you to do this easily?

Thanks,
Vincent

Jean-Philippe Archibald · January 23rd, 2004, 12:26 PM

Vincent,

Zoom in your subject at the maximum value, set up your focus (turn auto focus off), and if the distance between the subject and the camcorder remain the same, you won't loose your focus while zooming in and out.

David Ho · January 23rd, 2004, 12:54 PM

Hmm... this may be related to the same topic, but I also have another question. Some cameras present both a zoom and a manual focus ring, like the VX2100. Now, on the GL2, it only has a focus ring, and I've read some reviews that both of these cameras you cannot override the focus ring. What does this mean? Does this mean you can't keep focus while zooming or you cannot position where you want your focus to be?

Bill Pryor · January 23rd, 2004, 02:08 PM

You first zoom in all the way to your subject, get critical focus (manually of course), then zoom back to your wide angle and do your zoom shot. If it's a decent lens, it will stay in focus. Some of the early "prosumer" cameras had a problem with critical focus while zooming, but I think all the newer ones work they way they're supposed to. I had trouble maintaining focus with an early XL1 and VX1000 a few years ago, but all other 1/3" chip cameras I've used work fine.

Rob Lohman · January 25th, 2004, 09:03 AM

A great help to answer your question might be to let us know
which camera and lens you are using...

Joseph Lawrence · January 26th, 2004, 09:38 AM

I'm not certain if Vincent is experiencing what I've noticed
with my GL2.

I can only speak about the Canon GL2 and the Sony PD150. I
have tried to use the zoom rocker and the manual focus ring
simultaneously and these cameras won't let you adjust focus
manually while zooming. Once the zoom is engaged, twisting
the manual focus ring has no affect. I've experimented with
using a LANC controller. Yes, I have the focus set to manual.
As soon as I release the zoom rocker, the manual focus ring
will reactivate. I suspect some conflict between the zoom and
focus motors. If others have made a simultaneous zoom/focus
with these cameras, then I would certainly like to know the
technique.

Thanks

Joseph

Chris Hurd · January 26th, 2004, 09:59 AM

Howdy from Texas,

Due to the way these lenses work, it is *not possible* to pull focus and zoom at the same time on any prosumer camcorder using an auto-servo lens. This holds true for 3CCD camcorders such as the Canon GL1, GL2, Sony PD170, VX2000, etc. on down to the consumer 1CCD camcorders. Also true for the Canon 16x automatic (white) lens. It does not matter if there are separate manual focus and/or zoom rings nor does it matter if you're using a remote LANC lens controller; it simply isn't possible.

On the Canon 16x manual (black) lens and standard Fujinon or Canon 1/2" and 2/3" broadcast video lenses, it is possible and of course very common to pull focus and zoom at the same time. Hope this helps,

Bill Pryor · January 26th, 2004, 10:16 AM

That's why electronic lenses are so annoying. However, with some practice you can make them work in most cases. But these are two issues--one, maintaining critical focus and the other doing a focus shift. The lens either maintains critical focus or it doesn't because there's no back focus adjustment. I do have personal knowledge of one early XL1 that would't work right and the owner sent it in, and they adjusted back focus or replaced the lens or something, and it worked better, although you still could'nt zoom in, focus, and zoom out all the way and keep it totally sharp. I assume the newer models are better at that; I know the PD150s I've seen all seem to work fine.

As far as shifting focus, what I do with a DSR250 is zoom in, pan, and hit the auto focus button and let the lens shift itself electronically. This works in most situations, but obviously not in all. For example, if you zoom and pan and end up with a composition in which you want the subject way over to the side, then the auto focus will screw you up.

I rarely use the 250 for a dolly or jib shot, but there have been a few situations in which I did because with the wide angle adapter I could get right up a few inches from a person's nose and keep focus, wheras my camera with the real lens won't do that. I did a jib shot in which I boomed from a really extreme shot right in the person's face to a really high, wide angle with the camera moving up to the ceiling. There was no way to follow focus on the move, so I thought, what the heck, I'll try it on auto. Because of the particular situation, the auto focus kept it right on. So if you're careful and work on it, you can learn to use the electronic lenses for most things. I wouldn't trade one for a real lens, but you can live with their limitations in most cases, if you have to.

Rob Hester · January 30th, 2004, 03:32 AM

Quote:

Due to the way these lenses work, it is *not possible* to pull focus and zoom at the same time on any prosumer camcorder using an auto-servo lens

I read this and then tried it with my camera and I can do both at the same time. Zooming and manually focusing.

Am I missing something here?
Thanks,
Rob

Chris Hurd · January 30th, 2004, 07:44 AM

*shrug* I don't know, Rob, there are always exceptions I guess. That camcorder does not have LANC, which might be part of the explanation. Plus one of it's features is a "real-touch manual focus ring" which might have something else to do with it -- I'm unfamiliar with that camcorder; it's a single-chip 1.3mp consumer piece.

Bill Pryor · January 30th, 2004, 10:11 AM

Sometimes you can hit it, but I should have elaborated. I was thinking about traditional focus pulling, where you zoom in to the second focus point, note the distance on your lens, and then when you shift focus the assistant or you if you're good can hit the mark easily. On most electronic lenses the focus ring is electronic and in most cases doesn't go to the same point twice in a row, and there are no marks. If you mark the lens, it usually doesn't work, and if you turn the ring back to your beginning focus point and then go back to your end focus, it's normally not the same.
I've been able to use the auto focus button carefully with a DSR250 for focus shift, and in most cases it works better than doing it manually. As I move off the foreground subject, I press the button and let the camera shift in as I move to the background subject. It won't work if the shot it too loose, but in many cases it works very well.

January 23rd, 2004, 12:18 PM	#1
Vincent Im New Boot Join Date: Jan 2004 Location: Sunnyvale, CA Posts: 19	focusing while zooming How do you go about keeping focus on a subject while zooming in/out? Do you have to use auto focus for this? How do you know auto focus won't be focusing on something else? Are there accessories that allows you to do this easily? Thanks, Vincent

January 23rd, 2004, 12:26 PM	#2
Jean-Philippe Archibald Trustee Join Date: Sep 2003 Location: Saguenay, Québec, Canada Posts: 1,051	Vincent, Zoom in your subject at the maximum value, set up your focus (turn auto focus off), and if the distance between the subject and the camcorder remain the same, you won't loose your focus while zooming in and out. __________________ Jean-Philippe Archibald http://www.jparchibald.com - http://www.vimeo.com/jparchib

January 23rd, 2004, 12:54 PM	#3
David Ho Major Player Join Date: Nov 2003 Location: Los Angeles, CA Posts: 354	Hmm... this may be related to the same topic, but I also have another question. Some cameras present both a zoom and a manual focus ring, like the VX2100. Now, on the GL2, it only has a focus ring, and I've read some reviews that both of these cameras you cannot override the focus ring. What does this mean? Does this mean you can't keep focus while zooming or you cannot position where you want your focus to be? __________________ "Everyone has a photographic memory. Some just don't have film."

January 25th, 2004, 09:03 AM	#5
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	A great help to answer your question might be to let us know which camera and lens you are using... __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

January 26th, 2004, 09:59 AM	#7
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,366 Images: 513	Howdy from Texas, Due to the way these lenses work, it is not possible to pull focus and zoom at the same time on any prosumer camcorder using an auto-servo lens. This holds true for 3CCD camcorders such as the Canon GL1, GL2, Sony PD170, VX2000, etc. on down to the consumer 1CCD camcorders. Also true for the Canon 16x automatic (white) lens. It does not matter if there are separate manual focus and/or zoom rings nor does it matter if you're using a remote LANC lens controller; it simply isn't possible. On the Canon 16x manual (black) lens and standard Fujinon or Canon 1/2" and 2/3" broadcast video lenses, it is possible and of course very common to pull focus and zoom at the same time. Hope this helps, __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

January 23rd, 2004, 02:08 PM	#4
Bill Pryor Contributor Join Date: Jan 2003 Location: Kansas City, MO Posts: 4,449	You first zoom in all the way to your subject, get critical focus (manually of course), then zoom back to your wide angle and do your zoom shot. If it's a decent lens, it will stay in focus. Some of the early "prosumer" cameras had a problem with critical focus while zooming, but I think all the newer ones work they way they're supposed to. I had trouble maintaining focus with an early XL1 and VX1000 a few years ago, but all other 1/3" chip cameras I've used work fine.

January 26th, 2004, 09:38 AM	#6
Joseph Lawrence Regular Crew Join Date: Oct 2003 Location: fort wayne, IN Posts: 50	I'm not certain if Vincent is experiencing what I've noticed with my GL2. I can only speak about the Canon GL2 and the Sony PD150. I have tried to use the zoom rocker and the manual focus ring simultaneously and these cameras won't let you adjust focus manually while zooming. Once the zoom is engaged, twisting the manual focus ring has no affect. I've experimented with using a LANC controller. Yes, I have the focus set to manual. As soon as I release the zoom rocker, the manual focus ring will reactivate. I suspect some conflict between the zoom and focus motors. If others have made a simultaneous zoom/focus with these cameras, then I would certainly like to know the technique. Thanks Joseph

January 26th, 2004, 10:16 AM	#8
Bill Pryor Contributor Join Date: Jan 2003 Location: Kansas City, MO Posts: 4,449	That's why electronic lenses are so annoying. However, with some practice you can make them work in most cases. But these are two issues--one, maintaining critical focus and the other doing a focus shift. The lens either maintains critical focus or it doesn't because there's no back focus adjustment. I do have personal knowledge of one early XL1 that would't work right and the owner sent it in, and they adjusted back focus or replaced the lens or something, and it worked better, although you still could'nt zoom in, focus, and zoom out all the way and keep it totally sharp. I assume the newer models are better at that; I know the PD150s I've seen all seem to work fine. As far as shifting focus, what I do with a DSR250 is zoom in, pan, and hit the auto focus button and let the lens shift itself electronically. This works in most situations, but obviously not in all. For example, if you zoom and pan and end up with a composition in which you want the subject way over to the side, then the auto focus will screw you up. I rarely use the 250 for a dolly or jib shot, but there have been a few situations in which I did because with the wide angle adapter I could get right up a few inches from a person's nose and keep focus, wheras my camera with the real lens won't do that. I did a jib shot in which I boomed from a really extreme shot right in the person's face to a really high, wide angle with the camera moving up to the ceiling. There was no way to follow focus on the move, so I thought, what the heck, I'll try it on auto. Because of the particular situation, the auto focus kept it right on. So if you're careful and work on it, you can learn to use the electronic lenses for most things. I wouldn't trade one for a real lens, but you can live with their limitations in most cases, if you have to.

January 30th, 2004, 07:44 AM	#10
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,366 Images: 513	shrug I don't know, Rob, there are always exceptions I guess. That camcorder does not have LANC, which might be part of the explanation. Plus one of it's features is a "real-touch manual focus ring" which might have something else to do with it -- I'm unfamiliar with that camcorder; it's a single-chip 1.3mp consumer piece. __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

January 30th, 2004, 10:11 AM	#11
Bill Pryor Contributor Join Date: Jan 2003 Location: Kansas City, MO Posts: 4,449	Sometimes you can hit it, but I should have elaborated. I was thinking about traditional focus pulling, where you zoom in to the second focus point, note the distance on your lens, and then when you shift focus the assistant or you if you're good can hit the mark easily. On most electronic lenses the focus ring is electronic and in most cases doesn't go to the same point twice in a row, and there are no marks. If you mark the lens, it usually doesn't work, and if you turn the ring back to your beginning focus point and then go back to your end focus, it's normally not the same. I've been able to use the auto focus button carefully with a DSR250 for focus shift, and in most cases it works better than doing it manually. As I move off the foreground subject, I press the button and let the camera shift in as I move to the background subject. It won't work if the shot it too loose, but in many cases it works very well.