XL1 / XL1S focus hunting backfocus problems

Simon Duncan · June 5th, 2007, 08:39 AM

But I even noticed certain drifting of focus in manual mode.

I focus on a particular point and notice that the focus can slip and even breath. That is without moving the zoom or focus ring.
It just appears on this camera no to be very solid.

Again could this be something which might be tightened up or addressed by giving the camera a service?

Don Palomaki · June 5th, 2007, 11:18 AM

If focus is drifting when nothing is going on, including changes in image content or zoom setting or lighting, then worth having the camcorder checked.

If you send it in for a check, it is helpful to also send in a tape with an example of what is happening.

Cole McDonald · June 5th, 2007, 05:50 PM

check to see if the lens is dirty as well...we had a lens that a friend had purchased off of ebay (it had a single large finger print on the inside of the back element...the screws were glued down as well...wonder why it was being sold?). It never got good focus ever when in auto due to this.

Jack Smith · June 5th, 2007, 09:10 PM

Make sure your not in green mode, as even if you set manual focus, the camera will stay in auto.Although there are many factors which can affect focus , the "breathing" sure sounds like autofocus.

Simon Duncan · June 5th, 2007, 11:21 PM

Hi Cole,

Just a question on cleaning the lens.

What do you use to clean the lens?

Are there any major Don'ts with cleaning these canon lens?
eg Materials or products to stay clear off.

Don Palomaki · June 6th, 2007, 07:31 AM

Clean as you would a lens on a high quality still camera.

Cole McDonald · June 6th, 2007, 09:33 AM

that one, we didn't...we sent it back for a refund and purchased a different camera.

Jan Mitacek · June 21st, 2007, 02:03 AM

I'm experiencing this problem:

I'm in full wide. I set the focus to auto - focus is adjusted automatically. Then I set the focus to manual, then I zoom to full tele not even touching the focus ring. When zooming, the lens is going more and more out of focus, BUT in almost full tele the picture is suddenly sharp again and in full tele it is blured again.

I think the alignment of the lens and body is bad and should be adjusted. But I don't understand, why ther is this "sharp" in almost full tele. Your ideas are welcome.

Don Palomaki · June 21st, 2007, 12:22 PM

Depth of field/focus is greatest at wide angle settings so focus accuracy is not as important or apparent. The accuracy of focus is most apparent at full telephoto setting due to the much reduced depth of focus.

The normal procedure for setting focus is to zoom in fully on the subject of interest, focus, than adjust zoom as needed to compose the shot. With this done, the focus should be good through out the zoom range. If it is not, the backfocus setting is off, and for the XL1 series with the stock auto lens, it means a trip for service (special tools requiredm; however, the manual lenses do provide for user back focus adjustments).

In general, setting focus when at full wide angle zoom setting will not provide satisfactory results when you zoom in.

Why the change in focus to sharper and then to not as sharp in the zoom? Assuming the lens is otherwise in good condition, I do not know for sure but given that the lens element positions are computer and servo controlled based on a specific program for the lens motion, and different elements may move differently during the zoom, it likely relates to starting the zoom from what is effectively an "out of focus" position even though depth of field made it look like it was reasonably in focus.

Skip Hall · February 15th, 2009, 07:30 PM

Quote:

Originally Posted by Chris Hurd

Once you switch to manual focus, zoom all the way in on the farthest object from you. Press the "Push AF" button the side of the lens to set focus (you need *some* light for this). This is called "setting critical focus."

Zoom back out, and everything should stay in focus from here.

Hi Chris,
I know this has been addressed about a million times, but I thought I'd mention something that my XL-1 service guy told me. After inspecting and tuning up my camera, he told me that I shouldn't have focus-wander problems, if I use a procedure virtually identical to what you outlined above. However, he said that during the shoot, if I ever zoom the camera's lens in past about 80%, it was highly likely that the AF would lose its setting when I zoomed it back out again. This issue, he said, may become worse, if the zoom controls are operated quickly... going in or out (I think, is what he said).
I must confess to not understanding the mechanics behind this issue, but I certainly wish I could wish it away... but I can't.
I did test this information at my last dance recital shoot, however, and I believe his information is/was correct. My AF seemed to stay locked at the manually-set point, unless I zoomed in too far, or pulled back quickly.
But my eyesight (and the resulting "transitional" bifocal glasses!) makes it difficult to always discern perfect focus, even though I use the B&W viewfinder (as opposed to the stock one). I'll soon be working with a larger monitor at my station, so I can get a better sense of accuracy, but I thought I'd just drop in my two-cents worth... for whatever it's worth.

Thanks!

Skip Hall
Homeworks Video Productions
Suffolk, Virginia

June 5th, 2007, 11:18 AM	#272
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 3,310	If focus is drifting when nothing is going on, including changes in image content or zoom setting or lighting, then worth having the camcorder checked. If you send it in for a check, it is helpful to also send in a tape with an example of what is happening. __________________ dpalomaki@cox.net

June 5th, 2007, 05:50 PM	#273
Cole McDonald Trustee Join Date: Nov 2005 Location: Sauk Rapids, MN, USA Posts: 1,547	check to see if the lens is dirty as well...we had a lens that a friend had purchased off of ebay (it had a single large finger print on the inside of the back element...the screws were glued down as well...wonder why it was being sold?). It never got good focus ever when in auto due to this. __________________ http://www.yafiunderground.com Low/No Budget cinema that looks like a million bucks!

June 6th, 2007, 07:31 AM	#276
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 3,310	Clean as you would a lens on a high quality still camera. __________________ dpalomaki@cox.net

June 6th, 2007, 09:33 AM	#277
Cole McDonald Trustee Join Date: Nov 2005 Location: Sauk Rapids, MN, USA Posts: 1,547	that one, we didn't...we sent it back for a refund and purchased a different camera. __________________ http://www.yafiunderground.com Low/No Budget cinema that looks like a million bucks!

June 21st, 2007, 02:03 AM	#278
Jan Mitacek Tourist Join Date: Jun 2006 Location: Czech republic Posts: 4	XL1s 16x auto zoom focus problem I'm experiencing this problem: I'm in full wide. I set the focus to auto - focus is adjusted automatically. Then I set the focus to manual, then I zoom to full tele not even touching the focus ring. When zooming, the lens is going more and more out of focus, BUT in almost full tele the picture is suddenly sharp again and in full tele it is blured again. I think the alignment of the lens and body is bad and should be adjusted. But I don't understand, why ther is this "sharp" in almost full tele. Your ideas are welcome.

June 5th, 2007, 08:39 AM	#271
Simon Duncan Regular Crew Join Date: Dec 2005 Location: Angers, France Posts: 171	But I even noticed certain drifting of focus in manual mode. I focus on a particular point and notice that the focus can slip and even breath. That is without moving the zoom or focus ring. It just appears on this camera no to be very solid. Again could this be something which might be tightened up or addressed by giving the camera a service?

June 5th, 2007, 09:10 PM	#274
Jack Smith Major Player Join Date: Nov 2003 Location: ontario Posts: 417	Make sure your not in green mode, as even if you set manual focus, the camera will stay in auto.Although there are many factors which can affect focus , the "breathing" sure sounds like autofocus.

June 5th, 2007, 11:21 PM	#275
Simon Duncan Regular Crew Join Date: Dec 2005 Location: Angers, France Posts: 171	Hi Cole, Just a question on cleaning the lens. What do you use to clean the lens? Are there any major Don'ts with cleaning these canon lens? eg Materials or products to stay clear off.

June 21st, 2007, 12:22 PM	#279
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 3,310	Depth of field/focus is greatest at wide angle settings so focus accuracy is not as important or apparent. The accuracy of focus is most apparent at full telephoto setting due to the much reduced depth of focus. The normal procedure for setting focus is to zoom in fully on the subject of interest, focus, than adjust zoom as needed to compose the shot. With this done, the focus should be good through out the zoom range. If it is not, the backfocus setting is off, and for the XL1 series with the stock auto lens, it means a trip for service (special tools requiredm; however, the manual lenses do provide for user back focus adjustments). In general, setting focus when at full wide angle zoom setting will not provide satisfactory results when you zoom in. Why the change in focus to sharper and then to not as sharp in the zoom? Assuming the lens is otherwise in good condition, I do not know for sure but given that the lens element positions are computer and servo controlled based on a specific program for the lens motion, and different elements may move differently during the zoom, it likely relates to starting the zoom from what is effectively an "out of focus" position even though depth of field made it look like it was reasonably in focus. __________________ dpalomaki@cox.net

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