A GL-2 Imaging Bug / Attribute

Jeff Donald · May 28th, 2003, 03:50 PM

If you read my post above, you'll see that light fall off (key hole effect) will improve as you stop down the lens. You shot with it wide open (F1.6) so that is the maximum effect. It will be less noticeable as you stop down.

Joe Cirino · May 28th, 2003, 04:29 PM

Does this happen in Automatic? This does seem to be a problem. Its not like the strap is short or something...its acutally drawing your attention to its imperfection....

Jeff Donald · May 28th, 2003, 04:36 PM

I believe it will vary with each lens to some degree. It will occur as you zoom and be more pronounced if the lens is wide open (F1.6, F2.0 etc.). It will occur in automatic or any other mode, if you force the lens to be wide open. If you set the mode to AV (aperture priority) and set the lens to F5.6 or higher, the fall off should not be noticeable, even if you zoom.

Joe Cirino · May 28th, 2003, 04:43 PM

So basically, its even worse in low light because of this...

I am wondering if the extra 8X in a Gl2 is worth the quality loss overall to a VX2000?

I will be shooting day and night. Weddings, musicals, graduations, and maybe a short film. I hope Canon addresses this in the next month or so...

I really hate to get a lesser camera for the money.

I am a beginer and basically looking for a point and shoot camera from the go...

I heard that the Gl2 is this camera, but this is a downfall. No way to put it.

Joe Sacher · May 28th, 2003, 04:50 PM

I went down into the same lighting I shot earlier today to do some tests. I recorded video a minimum light for Wide, 1/4, 1/2, 3/4, and Full zoom with Image Stabilization on and off. Shot data is in the image for the shot. Here are the results:

http://joesacher.com/video/canon/canon.htm

I expected that the results might improve or stay the same when I turned IS off. In fact, it looks to me that I get less of a keyhole effect with IS on. That is not what I would expect.

Joe Sacher · May 28th, 2003, 04:54 PM

Cirino,

If your target is going to be video that plays on TV, then you will most likely never notice this. I shoot video for both TV and computer, but I always do a "TV safe" type of crop to the footage for computer. This is to keep the titles and such from looking stupid because of too much free space all around. I think it is something to be aware of, but not a real problem for me. The Movie Frame mode more than makes up for it over the VX2000 for me.

Ken Tanaka · May 28th, 2003, 04:54 PM

Those are very interesting results, Joe. Thanks for doing some lab work!

Gee, I can't imagine what some innocent visitor to that page might think it means...

Joe Sacher · May 28th, 2003, 04:58 PM

Yeah, my site gets indexed pretty well by Google. If they robot through DV Community, it should be indexed in a month of so. I'll just let them wonder, when they get there. :)

Jeff Donald · May 28th, 2003, 05:46 PM

First, let's start calling it by it's right name - Light Fall Off. The reason for this is that as professionals it reflects poorly on us to use improper or confusing names. Does your mechanic call spark plugs "those round sparky things in your engine." Do we call it a lens or "that round glass whatchamacallit on the end of my camera." This will make it easier to diagnose in the future and aid others who may stumble across this issue.

There is nothing Canon can do to fix this optical defect (except resign and manufacture a replacement camera). Light fall off is present in all optical systems. In other words every lens you own and will own for the foreseeable future, will have light fall off.

If you shoot for TV this is a non-issue. It's in the overscan and won't be seen. The GL2 is an NTSC video camera and as such meets requirements for that use. If you design for web or computer it may be an issue and you'll want to minimize it's effect by following my suggestions in the post above. In the tests the fall off is greatly reduced at F2 and probably gone at F2.8 or F4. Make sure not to do your web or computer work at F1.6, use a different F-stop and it's a non-issue.

Joe Cirino · May 28th, 2003, 06:06 PM

Thanks Jeff. This clears it up for me. GL2 it is!!

Thanks...

Steve Withers · May 28th, 2003, 07:29 PM

Setting the f-stop to 2.4 fixed the problem completely. Thanks Jeff.

Kurt Kober · August 2nd, 2003, 11:27 AM

Jeff, many thanks from another new boot. I was ready to freak out about this issue, but your quick f-stop edjumication saved the day. Back in love with my GL2! And thanks also Joe for posting the examples above.

Ryan Krga · August 21st, 2003, 04:45 AM

When I first got my GL2 this problem never occured until now. My waruntee is over and I don't know how to approach the problem. In every post within this topic I seem to find nothing that will fix the problem. When I zoom in about halfway there isn't a keyhole effect, the whole picture darkens! Most of my work is web oriented and I would hate to have to live with this problem or use different settings that I don't want to use on my GL2 just to get rid of the problem. Any suggestions?

Thank you very much.

Jeff Donald · August 21st, 2003, 05:58 AM

When the whole picture darkens, is the exposure in auto or manual? Try to duplicate the effect in auto and see if it goes away.

Ryan Krga · August 21st, 2003, 02:03 PM

This still was taken in full manual(S - 1/60, F - 1.6, DB - 0).

http://www.visital.com/keyhole/(Unknown) - Still 001.jpg

This still was taken in full auto.

http://www.visital.com/keyhole/(Unknown) - Still 002.jpg

May 28th, 2003, 03:50 PM	#46
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	If you read my post above, you'll see that light fall off (key hole effect) will improve as you stop down the lens. You shot with it wide open (F1.6) so that is the maximum effect. It will be less noticeable as you stop down. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

May 28th, 2003, 04:36 PM	#48
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	I believe it will vary with each lens to some degree. It will occur as you zoom and be more pronounced if the lens is wide open (F1.6, F2.0 etc.). It will occur in automatic or any other mode, if you force the lens to be wide open. If you set the mode to AV (aperture priority) and set the lens to F5.6 or higher, the fall off should not be noticeable, even if you zoom. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

May 28th, 2003, 04:54 PM	#52
Ken Tanaka Retired DV Info Net Almunus Join Date: Dec 2001 Location: Chicago, IL Posts: 6,943	Those are very interesting results, Joe. Thanks for doing some lab work! Gee, I can't imagine what some innocent visitor to that page might think it means... __________________ 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 28th, 2003, 05:46 PM	#54
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	First, let's start calling it by it's right name - Light Fall Off. The reason for this is that as professionals it reflects poorly on us to use improper or confusing names. Does your mechanic call spark plugs "those round sparky things in your engine." Do we call it a lens or "that round glass whatchamacallit on the end of my camera." This will make it easier to diagnose in the future and aid others who may stumble across this issue. There is nothing Canon can do to fix this optical defect (except resign and manufacture a replacement camera). Light fall off is present in all optical systems. In other words every lens you own and will own for the foreseeable future, will have light fall off. If you shoot for TV this is a non-issue. It's in the overscan and won't be seen. The GL2 is an NTSC video camera and as such meets requirements for that use. If you design for web or computer it may be an issue and you'll want to minimize it's effect by following my suggestions in the post above. In the tests the fall off is greatly reduced at F2 and probably gone at F2.8 or F4. Make sure not to do your web or computer work at F1.6, use a different F-stop and it's a non-issue. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

August 21st, 2003, 05:58 AM	#59
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	When the whole picture darkens, is the exposure in auto or manual? Try to duplicate the effect in auto and see if it goes away. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

May 28th, 2003, 04:29 PM	#47
Joe Cirino Regular Crew Join Date: Apr 2003 Location: United States Posts: 101	Does this happen in Automatic? This does seem to be a problem. Its not like the strap is short or something...its acutally drawing your attention to its imperfection....

May 28th, 2003, 04:43 PM	#49
Joe Cirino Regular Crew Join Date: Apr 2003 Location: United States Posts: 101	So basically, its even worse in low light because of this... I am wondering if the extra 8X in a Gl2 is worth the quality loss overall to a VX2000? I will be shooting day and night. Weddings, musicals, graduations, and maybe a short film. I hope Canon addresses this in the next month or so... I really hate to get a lesser camera for the money. I am a beginer and basically looking for a point and shoot camera from the go... I heard that the Gl2 is this camera, but this is a downfall. No way to put it.

May 28th, 2003, 04:50 PM	#50
Joe Sacher Regular Crew Join Date: May 2003 Location: Indianapolis, IN Posts: 177	I went down into the same lighting I shot earlier today to do some tests. I recorded video a minimum light for Wide, 1/4, 1/2, 3/4, and Full zoom with Image Stabilization on and off. Shot data is in the image for the shot. Here are the results: http://joesacher.com/video/canon/canon.htm I expected that the results might improve or stay the same when I turned IS off. In fact, it looks to me that I get less of a keyhole effect with IS on. That is not what I would expect.

May 28th, 2003, 04:58 PM	#53
Joe Sacher Regular Crew Join Date: May 2003 Location: Indianapolis, IN Posts: 177	Yeah, my site gets indexed pretty well by Google. If they robot through DV Community, it should be indexed in a month of so. I'll just let them wonder, when they get there. :)

May 28th, 2003, 06:06 PM	#55
Joe Cirino Regular Crew Join Date: Apr 2003 Location: United States Posts: 101	Thanks Jeff. This clears it up for me. GL2 it is!! Thanks...

May 28th, 2003, 07:29 PM	#56
Steve Withers Regular Crew Join Date: May 2003 Location: New Haven, CT, USA Posts: 59	Setting the f-stop to 2.4 fixed the problem completely. Thanks Jeff.

August 2nd, 2003, 11:27 AM	#57
Kurt Kober New Boot Join Date: Jul 2003 Location: Central, New Jersey Posts: 7	Jeff, many thanks from another new boot. I was ready to freak out about this issue, but your quick f-stop edjumication saved the day. Back in love with my GL2! And thanks also Joe for posting the examples above.

August 21st, 2003, 04:45 AM	#58
Ryan Krga Regular Crew Join Date: Jan 2003 Location: Chicago, Illinois Posts: 116	When I first got my GL2 this problem never occured until now. My waruntee is over and I don't know how to approach the problem. In every post within this topic I seem to find nothing that will fix the problem. When I zoom in about halfway there isn't a keyhole effect, the whole picture darkens! Most of my work is web oriented and I would hate to have to live with this problem or use different settings that I don't want to use on my GL2 just to get rid of the problem. Any suggestions? Thank you very much.

August 21st, 2003, 02:03 PM	#60
Ryan Krga Regular Crew Join Date: Jan 2003 Location: Chicago, Illinois Posts: 116	This still was taken in full manual(S - 1/60, F - 1.6, DB - 0). http://www.visital.com/keyhole/(Unknown) - Still 001.jpg This still was taken in full auto. http://www.visital.com/keyhole/(Unknown) - Still 002.jpg