XL1s focusing algorithm? at DVinfo.net

Ron Transco · May 24th, 2002, 08:37 AM

Can anyone point me to an article on the focusing algorithm that Canon uses on the XL1s? I'd like to get a feel for what it is doing.

I'm unable to get consistantly sharp manual focus using the supplied EVF; it just isn't clear enough. What I'm doing now is zooming out to fill as much of the frame as possible with my primary subject, hit the AF button, then zoom back to compose my shot. Focus still looks off, especially at the larger aperatures. Suggestions?

Ken Tanaka · May 24th, 2002, 09:27 AM

Zooming IN to pull focus is absolutely the correct maneuver.

Part of your problem -may- be due to the XL1s' color viewfinder. This is a legendary problem in which the relatively low-resolution of the color lcd viewfinder always looks just a bit soft to some eyes and on some subjects. This is fundamentally why all professional cameras have high-resolution b&w crt viewfinders. An excellent b&w viewfinder is available for the XL1s but it is a rather pricey item.

Part may also be due to the 16x lens' focus itself. The lens' back-focus may not be properly calibrated (at the factory), the servos may be slightly off, etc.

My suggestion is to shoot a test tape with various subjects, lighting and focal lengths to determine if it's the lens, the vf or your eyes. Inspect the footage closely on an NTSC monitor. If it looks like the camera/lens is faulty contact Canon's service org to get it fixed up. They can sometimes work miracles in such cases.

Unfortunately, yours is a very common problem.

Ron Transco · May 24th, 2002, 02:34 PM

Ken -

Thanks for the advice. Every once in a while I nail the focus and the shot is sharp as a tack; i.e. the camera / lens has the potential. I'm afraid you are probably right about the color EVF. I can't afford the B/W finder, so I guess it comes down to tuning my technique. I just bought the camera and haven't taken the time to run a series of test shots to see what works best; I guess it's time... Nice to know I'm not the only one with this problem.

Ken Tanaka · May 24th, 2002, 02:49 PM

Ron,
Since your camera is still factory-fresh, it's worth reiterating that the back-focus -may- be a culprit. If, when under manual focus, you get a laser-sharp focus when zoomed-in but it goes mushy when you go wide you may need to have the lens adjusted by Canon.

Good luck.

John Klein · May 24th, 2002, 06:05 PM

I've learned that I need to Push AF at each focal length. Looks better now.

PS. I find that if I zoom out from a focus, it's not that bad; but if I zoom in from a focus, that's where it's way off.

whiterabbit · June 4th, 2002, 07:45 PM

The focus is my one biggest gripe with this camera and I have just wrote it off as being one of the cameras traits. I read the article on focusing with the canon but really will be happy when I can afford the full manual lense and BW viewfinder.

Another problem I am having is with exposure. When I go by the dashed lines and set it to dead middle It looks dark. I put it on my computer and it is dark so now my display remains turned off. Everything I do with this camera is by feel from testing. I wont buy another...even if I do like the camera, it scares me to be in this zen meditation state all the time.

Now I just read about backfocus and how that can throw things off. I dont know what this is and am wondering how much is it going to cost to fix (if that is the problem). My camera is probably out of warranty. I expect with so many people having this problem that its not the back focus but just the viewfinder and the tricky auto lense. The auto focus can work very well in good bright light by the way but Im mostly a full manual kind of shooter.

Anyway these days I seem to have the focus thing down but I have imagined many times the great feeling its gonna be to be able to use the viewfinder again. One of the things I also do when possible is use an external monitor. Anyone have any other tricks I can try.

cheers

May 24th, 2002, 08:37 AM	#1
Ron Transco Regular Crew Join Date: May 2002 Posts: 53	XL1s focusing algorithm? Can anyone point me to an article on the focusing algorithm that Canon uses on the XL1s? I'd like to get a feel for what it is doing. I'm unable to get consistantly sharp manual focus using the supplied EVF; it just isn't clear enough. What I'm doing now is zooming out to fill as much of the frame as possible with my primary subject, hit the AF button, then zoom back to compose my shot. Focus still looks off, especially at the larger aperatures. Suggestions? __________________ Ron

May 24th, 2002, 09:27 AM	#2
Ken Tanaka Retired DV Info Net Almunus Join Date: Dec 2001 Location: Chicago, IL Posts: 6,943	Zooming IN to pull focus is absolutely the correct maneuver. Part of your problem -may- be due to the XL1s' color viewfinder. This is a legendary problem in which the relatively low-resolution of the color lcd viewfinder always looks just a bit soft to some eyes and on some subjects. This is fundamentally why all professional cameras have high-resolution b&w crt viewfinders. An excellent b&w viewfinder is available for the XL1s but it is a rather pricey item. Part may also be due to the 16x lens' focus itself. The lens' back-focus may not be properly calibrated (at the factory), the servos may be slightly off, etc. My suggestion is to shoot a test tape with various subjects, lighting and focal lengths to determine if it's the lens, the vf or your eyes. Inspect the footage closely on an NTSC monitor. If it looks like the camera/lens is faulty contact Canon's service org to get it fixed up. They can sometimes work miracles in such cases. Unfortunately, yours is a very common problem. __________________ Lady X Films: A lady with a boring wardrobe...and a global mission. Hey, you don't have enough stuff! Buy with confidence from our sponsors. Hand-picked as the best in the business...Really! See some of my work one frame at a time: www.KenTanaka.com

May 24th, 2002, 02:34 PM	#3
Ron Transco Regular Crew Join Date: May 2002 Posts: 53	Ken - Thanks for the advice. Every once in a while I nail the focus and the shot is sharp as a tack; i.e. the camera / lens has the potential. I'm afraid you are probably right about the color EVF. I can't afford the B/W finder, so I guess it comes down to tuning my technique. I just bought the camera and haven't taken the time to run a series of test shots to see what works best; I guess it's time... Nice to know I'm not the only one with this problem. __________________ Ron

May 24th, 2002, 02:49 PM	#4
Ken Tanaka Retired DV Info Net Almunus Join Date: Dec 2001 Location: Chicago, IL Posts: 6,943	Ron, Since your camera is still factory-fresh, it's worth reiterating that the back-focus -may- be a culprit. If, when under manual focus, you get a laser-sharp focus when zoomed-in but it goes mushy when you go wide you may need to have the lens adjusted by Canon. Good luck. __________________ Lady X Films: A lady with a boring wardrobe...and a global mission. Hey, you don't have enough stuff! Buy with confidence from our sponsors. Hand-picked as the best in the business...Really! See some of my work one frame at a time: www.KenTanaka.com

May 24th, 2002, 06:05 PM	#5
John Klein Regular Crew Join Date: Dec 2001 Location: Wisconsin, USA Posts: 182	I've learned that I need to Push AF at each focal length. Looks better now. PS. I find that if I zoom out from a focus, it's not that bad; but if I zoom in from a focus, that's where it's way off. __________________ < >< . . . . . < >< . . . . . < ><

June 4th, 2002, 07:45 PM	#6
whiterabbit Regular Crew Join Date: Jun 2002 Location: Miami Posts: 37	The focus is my one biggest gripe with this camera and I have just wrote it off as being one of the cameras traits. I read the article on focusing with the canon but really will be happy when I can afford the full manual lense and BW viewfinder. Another problem I am having is with exposure. When I go by the dashed lines and set it to dead middle It looks dark. I put it on my computer and it is dark so now my display remains turned off. Everything I do with this camera is by feel from testing. I wont buy another...even if I do like the camera, it scares me to be in this zen meditation state all the time. Now I just read about backfocus and how that can throw things off. I dont know what this is and am wondering how much is it going to cost to fix (if that is the problem). My camera is probably out of warranty. I expect with so many people having this problem that its not the back focus but just the viewfinder and the tricky auto lense. The auto focus can work very well in good bright light by the way but Im mostly a full manual kind of shooter. Anyway these days I seem to have the focus thing down but I have imagined many times the great feeling its gonna be to be able to use the viewfinder again. One of the things I also do when possible is use an external monitor. Anyone have any other tricks I can try. cheers