Have you seen this flickering in your video? at DVinfo.net

David Chiu · January 22nd, 2010, 08:46 AM

I bought 7D for 2 months and bought it to Japan for vacation. But I don't know why the video would look flickering when I zoomed out. It happens even when I use M mode; everything is knocked. The video below shows this flickering at the beginning when I zoomed out wide of the Japanese robot.

YouTube - Test 7D.wmv

Jason McDonald · January 22nd, 2010, 09:42 AM

What lens do you have on the camera. Is it one that varies in aperture?

David Chiu · January 22nd, 2010, 10:09 AM

The lens I used was the Canon kit lens EF-S 15-85 mm 3.5 - 5.6 IS USM.
This flickering is not a closing of aperature but alternating darkening and brightening of the video as can be seen in the video.

Perrone Ford · January 22nd, 2010, 10:15 AM

Quote:

Originally Posted by David Chiu

The lens I used was the Canon kit lens EF-S 15-85 mm 3.5 - 5.6 IS USM.
This flickering is not a closing of aperature but alternating darkening and brightening of the video as can be seen in the video.

Jason's question was right on the money. Looks like two things going on.

1. Variable aperature lens
2. Camera set to automatic exposure mode trying to compensate for the lens.

David Chiu · January 22nd, 2010, 10:37 AM

The camera was set to M mode, which should knock both the aperture and shutter speed down. Moreover, shooting upward to the face and then facing the sun at the background do not lead to closing of the aperture further. After seeing the face of the robot, the zoom was already at the widest possible point.

Bill Binder · January 22nd, 2010, 10:43 AM

Auto ISO? It will do this in Full Manual if enabled.

Chuck Spaulding · January 22nd, 2010, 12:21 PM

I'm not an expert on these (Still) lenses, however what I think your seeing is that even though you have the camera set to Manual, the Iris is still stopping down because you do not have a, for a lack of the proper technical term, "constant" speed lens. It's not an f/2.8 throughout the entire zoom range..

So if your using the kit lens it is f/3.5 at one end and f/5.6 at the other, so your seeing the change.

Just a thought...

Wm. Turner · January 22nd, 2010, 04:56 PM

I think Chuck is right. If you set your F-Stop to f/3.5 and you're fully wide on the lens, it's going to try to keep the lens as open as it can while you zoom in. On the Kit lens the more you zoom in the more it get stopped down. So when you're at 85mm it's going to be at f/5.6, when you zoom out it's going to open up again. The only work around for this problem on this lens is to just set it to f/5.6 when you do a zoom like that to avoid the issue.

Jason McDonald · January 22nd, 2010, 08:47 PM

Best way to test this is to do a quick zoom in and out on manual with the aperture at 3.5f and see if you get that flicker. The set the aperture at 5.6f and see if you get the same results. Auto ISO is another thing to check.

Chuck Spaulding · January 22nd, 2010, 09:08 PM

Another way to test this is to set your f-stop where you want it, press the DOF preview button, which opens the iris to that f-stop and at the same time twist the lens about 1/4 of a turn, as though your removing it. This disengages the auto functions on the lens.

Bruce Foreman · January 23rd, 2010, 12:19 AM

With ISO set to AUTO, and the camera in Manual mode the exposure is NOT "locked". You will see brightness changes occur from anything that affects exposure. Zooming is one thing and panning from one area of brightness to another will cause brightness changes.

These brightness changes are not instantaneous either and that explains the "flickering" effect seen in this segment.

The cure is twofold. As suggested above manually set the aperture at the widest opening available on the telephoto end so the camera is not trying to react to what is senses as a physical aperture change.

The other thing to do is press the ISO button on top and a "table" appears with all of the ISO values. If AUTO is selected move the cursor bar to the ISO value that appears on the lower right (I don't have my 7D in front of me) when you partially depress the shutter release. Setting a specific ISO value in Manual mode will "lock" exposure and you won't see the camera trying to adjust to lighting changes.

Hope this helps.

David Chiu · January 23rd, 2010, 11:35 AM

Wow thank you guys for all the suggestions. I'll try what you all suggested and see if I can 'lock' the supposingly 'Manual' mode further.

Ryan Postel · January 25th, 2010, 01:38 PM

The camera is on Manual, its the lens that's causing the issue. With a constant aperature zoom lens, this same shot would've been fine.

Jean-Philippe Archibald · January 26th, 2010, 08:30 AM

Yes it's the lens. And even if you set the aperture to f5.6 at the widest position, you will still get flicker when you zoom. I don't know why, but I experienced the same thing with several lenses here. The only way to use the zoom on the canon DSLRs is with aperture-fixed lenses, like the 18-55 f2.8, 70-200 f.2.8, etc.

With the kit lens, you must use it like a prime. Frame your shot, record, stop record, reframe your shot, record.

David Chiu · February 1st, 2010, 10:54 AM

I experience the same problem as Jean-Philippe Archibald does. I locked everything, including using M mode, fixed ISO, and closed the aperature to 5.6, and found that the flickering occurred when I zoomed in or out.

I also twisted the lens about 1/4 of a turn to disengage the auto functions on the lens as Chuck Spaulding mentioned, the flickering disappeared. Turning back the lens into the fully engaged position, the flickering appeared again when zoomed in or out. And I could see darkening of the picture when I zoomed in as the aperture was down from 3.5 to 5.6. The flickering did not happen when I used a fixed focal length lens.

It seems like it is related to the communication between the lens and the body.

January 22nd, 2010, 08:46 AM	#1
David Chiu New Boot Join Date: Feb 2009 Location: Hong Kong, China Posts: 6	Have you seen this flickering in your video? I bought 7D for 2 months and bought it to Japan for vacation. But I don't know why the video would look flickering when I zoomed out. It happens even when I use M mode; everything is knocked. The video below shows this flickering at the beginning when I zoomed out wide of the Japanese robot. YouTube - Test 7D.wmv Last edited by David Chiu; January 22nd, 2010 at 08:48 AM. Reason: A mistake in the embedded video

January 22nd, 2010, 10:43 AM	#6
Bill Binder Major Player Join Date: Jun 2005 Location: San Francisco Posts: 542	Auto ISO? It will do this in Full Manual if enabled. __________________ BayTaper.com \| One man's multimedia journey through the San Francisco live jazz and creative music scene.

January 26th, 2010, 08:30 AM	#14
Jean-Philippe Archibald Trustee Join Date: Sep 2003 Location: Saguenay, Québec, Canada Posts: 1,051	Yes it's the lens. And even if you set the aperture to f5.6 at the widest position, you will still get flicker when you zoom. I don't know why, but I experienced the same thing with several lenses here. The only way to use the zoom on the canon DSLRs is with aperture-fixed lenses, like the 18-55 f2.8, 70-200 f.2.8, etc. With the kit lens, you must use it like a prime. Frame your shot, record, stop record, reframe your shot, record. __________________ Jean-Philippe Archibald http://www.jparchibald.com - http://www.vimeo.com/jparchib

January 22nd, 2010, 09:42 AM	#2
Jason McDonald Major Player Join Date: Jul 2009 Location: Japan Posts: 295	What lens do you have on the camera. Is it one that varies in aperture?

January 22nd, 2010, 10:09 AM	#3
David Chiu New Boot Join Date: Feb 2009 Location: Hong Kong, China Posts: 6	The lens I used was the Canon kit lens EF-S 15-85 mm 3.5 - 5.6 IS USM. This flickering is not a closing of aperature but alternating darkening and brightening of the video as can be seen in the video.

January 22nd, 2010, 10:37 AM	#5
David Chiu New Boot Join Date: Feb 2009 Location: Hong Kong, China Posts: 6	The camera was set to M mode, which should knock both the aperture and shutter speed down. Moreover, shooting upward to the face and then facing the sun at the background do not lead to closing of the aperture further. After seeing the face of the robot, the zoom was already at the widest possible point.

January 22nd, 2010, 12:21 PM	#7
Chuck Spaulding Trustee Join Date: Nov 2004 Location: Thousand Oaks Posts: 1,104	I'm not an expert on these (Still) lenses, however what I think your seeing is that even though you have the camera set to Manual, the Iris is still stopping down because you do not have a, for a lack of the proper technical term, "constant" speed lens. It's not an f/2.8 throughout the entire zoom range.. So if your using the kit lens it is f/3.5 at one end and f/5.6 at the other, so your seeing the change. Just a thought...

January 22nd, 2010, 04:56 PM	#8
Wm. Turner New Boot Join Date: Oct 2006 Location: Los Angeles, CA Posts: 11	I think Chuck is right. If you set your F-Stop to f/3.5 and you're fully wide on the lens, it's going to try to keep the lens as open as it can while you zoom in. On the Kit lens the more you zoom in the more it get stopped down. So when you're at 85mm it's going to be at f/5.6, when you zoom out it's going to open up again. The only work around for this problem on this lens is to just set it to f/5.6 when you do a zoom like that to avoid the issue.

January 22nd, 2010, 08:47 PM	#9
Jason McDonald Major Player Join Date: Jul 2009 Location: Japan Posts: 295	Best way to test this is to do a quick zoom in and out on manual with the aperture at 3.5f and see if you get that flicker. The set the aperture at 5.6f and see if you get the same results. Auto ISO is another thing to check.

January 22nd, 2010, 09:08 PM	#10
Chuck Spaulding Trustee Join Date: Nov 2004 Location: Thousand Oaks Posts: 1,104	Another way to test this is to set your f-stop where you want it, press the DOF preview button, which opens the iris to that f-stop and at the same time twist the lens about 1/4 of a turn, as though your removing it. This disengages the auto functions on the lens.

January 23rd, 2010, 12:19 AM	#11
Bruce Foreman Trustee Join Date: Nov 2006 Location: San Angelo Texas Posts: 1,518	With ISO set to AUTO, and the camera in Manual mode the exposure is NOT "locked". You will see brightness changes occur from anything that affects exposure. Zooming is one thing and panning from one area of brightness to another will cause brightness changes. These brightness changes are not instantaneous either and that explains the "flickering" effect seen in this segment. The cure is twofold. As suggested above manually set the aperture at the widest opening available on the telephoto end so the camera is not trying to react to what is senses as a physical aperture change. The other thing to do is press the ISO button on top and a "table" appears with all of the ISO values. If AUTO is selected move the cursor bar to the ISO value that appears on the lower right (I don't have my 7D in front of me) when you partially depress the shutter release. Setting a specific ISO value in Manual mode will "lock" exposure and you won't see the camera trying to adjust to lighting changes. Hope this helps.

January 23rd, 2010, 11:35 AM	#12
David Chiu New Boot Join Date: Feb 2009 Location: Hong Kong, China Posts: 6	Wow thank you guys for all the suggestions. I'll try what you all suggested and see if I can 'lock' the supposingly 'Manual' mode further.

January 25th, 2010, 01:38 PM	#13
Ryan Postel Regular Crew Join Date: Feb 2008 Location: Chicago, IL Posts: 93	The camera is on Manual, its the lens that's causing the issue. With a constant aperature zoom lens, this same shot would've been fine.

February 1st, 2010, 10:54 AM	#15
David Chiu New Boot Join Date: Feb 2009 Location: Hong Kong, China Posts: 6	I experience the same problem as Jean-Philippe Archibald does. I locked everything, including using M mode, fixed ISO, and closed the aperature to 5.6, and found that the flickering occurred when I zoomed in or out. I also twisted the lens about 1/4 of a turn to disengage the auto functions on the lens as Chuck Spaulding mentioned, the flickering disappeared. Turning back the lens into the fully engaged position, the flickering appeared again when zoomed in or out. And I could see darkening of the picture when I zoomed in as the aperture was down from 3.5 to 5.6. The flickering did not happen when I used a fixed focal length lens. It seems like it is related to the communication between the lens and the body.