"strobing" from 7D at DVinfo.net

Dan Shallenberger · May 9th, 2010, 10:07 PM

I've noticed something I'm curious if anyone else has experienced. I'm shooting in 1280/60p with a shutter speed 60 and 2.8 aperture on my 7D, and every now and then I notice some strobing while recording. When I notice it, I stop the recording, then start again immediately, and it's usually gone. Sometimes I don't notice it till I get into post though, which really sucks. I'm glad I'm not shooting anything critical at weddings with this 7D yet.

Anyone else notice this?

Jeremy Hughes · May 10th, 2010, 01:01 AM

do you mean you can actually see it happening in the monitor? I haven't had that issue at all. Something to look out for but the fact that you get it, stop the recording and then restart sounds like an issue with the sensor not reading fast enough. I might contact Canon on that one and find out if its something they know of or an issue they should take a look at your camera through warranty on.

Norman Pogson · May 10th, 2010, 05:06 AM

At 60p I always use a shutter speed of 120 and always slow the footage down in post to 30p, I don't see any effects.

Dan Shallenberger · May 10th, 2010, 07:15 AM

Yep, I can actually see it on the lcd screen. I thought maybe it was just a slow refresh on the lcd screen, so I ignored it. But then saw it in some of the footage. So, my next shoot (which was last Saturday) I looked for it, and when I saw it on the lcd screen, I stopped rolling and restarted. That usually took care of it, and the footage after doing that is fine.

This is crazy. I'm so busy with shoots over the next few months, and sending my camera in for a few weeks would really be tough. But it's better than that strobing I'm getting.

I'm going to try 1080/30p today and see if I get the same thing. I imagine I will, but it's worth a try.

Bill Pryor · May 10th, 2010, 03:01 PM

If you're shooting at 60 fps, I believe your shutter speed should be 1/120.

Dan Shallenberger · May 14th, 2010, 08:54 PM

Ok, I did more testing, and I'm getting this "strobing" effect no matter the frame rate or resolution. Then I decided to try something different. I went and bought a mini-hdmi to hdmi cable and plugged the 7D directly into my hdtv. Hmm, no strobing at all. Nothing but silky smooth playback.

So, apparently it's my computer. I have yet to render any 7d footage to a finished file or dvd... just been testing it in quicktime. I have the newest quad-core mac pro with 6gb of ram. So, would this be my processing power slowing me down, or the video card?

Manus Sweeney · May 15th, 2010, 02:27 AM

strobing is usually a result of a clash in shutter speed/ framerate with certain types of artificial light.. Are you noticing the effect under the same light source always? Try experimenting with other shutter speeds and it should fix it, otherwise post a video and it should be possible to say what the source of the problem is.

Jon Bickford · May 19th, 2010, 01:49 AM

yeah I get it sometimes under different odd lighting situations, lights pulsing out of frequency with the sensors i guess, i have also noticed that if i ramp the shutter speed up and then back down it usually goes away, weird. let us know if you find out anything.

May 9th, 2010, 10:07 PM	#1
Dan Shallenberger Major Player Join Date: Mar 2005 Location: Cincinnati, OH Posts: 253	"strobing" from 7D I've noticed something I'm curious if anyone else has experienced. I'm shooting in 1280/60p with a shutter speed 60 and 2.8 aperture on my 7D, and every now and then I notice some strobing while recording. When I notice it, I stop the recording, then start again immediately, and it's usually gone. Sometimes I don't notice it till I get into post though, which really sucks. I'm glad I'm not shooting anything critical at weddings with this 7D yet. Anyone else notice this?

May 10th, 2010, 01:01 AM	#2
Jeremy Hughes Major Player Join Date: Nov 2005 Location: Columbus, Ohio Posts: 276 Images: 2	do you mean you can actually see it happening in the monitor? I haven't had that issue at all. Something to look out for but the fact that you get it, stop the recording and then restart sounds like an issue with the sensor not reading fast enough. I might contact Canon on that one and find out if its something they know of or an issue they should take a look at your camera through warranty on. __________________ www.elevate-m.com filmvideostuff.blogspot.com

May 10th, 2010, 05:06 AM	#3
Norman Pogson Regular Crew Join Date: Feb 2010 Location: Ottawa, Canada Posts: 140	At 60p I always use a shutter speed of 120 and always slow the footage down in post to 30p, I don't see any effects. __________________ My Stock Video Blog Linkedin

May 19th, 2010, 01:49 AM	#8
Jon Bickford Major Player Join Date: Nov 2004 Location: Las Vegas, NV., Los Angeles, CA, Posts: 220	yeah I get it sometimes under different odd lighting situations, lights pulsing out of frequency with the sensors i guess, i have also noticed that if i ramp the shutter speed up and then back down it usually goes away, weird. let us know if you find out anything. __________________ Jon Bickford, Trepany Films San Pedro, CA Trephine001@aol.com

May 10th, 2010, 07:15 AM	#4
Dan Shallenberger Major Player Join Date: Mar 2005 Location: Cincinnati, OH Posts: 253	Yep, I can actually see it on the lcd screen. I thought maybe it was just a slow refresh on the lcd screen, so I ignored it. But then saw it in some of the footage. So, my next shoot (which was last Saturday) I looked for it, and when I saw it on the lcd screen, I stopped rolling and restarted. That usually took care of it, and the footage after doing that is fine. This is crazy. I'm so busy with shoots over the next few months, and sending my camera in for a few weeks would really be tough. But it's better than that strobing I'm getting. I'm going to try 1080/30p today and see if I get the same thing. I imagine I will, but it's worth a try.

May 10th, 2010, 03:01 PM	#5
Bill Pryor Contributor Join Date: Jan 2003 Location: Kansas City, MO Posts: 4,449	If you're shooting at 60 fps, I believe your shutter speed should be 1/120.

May 14th, 2010, 08:54 PM	#6
Dan Shallenberger Major Player Join Date: Mar 2005 Location: Cincinnati, OH Posts: 253	Ok, I did more testing, and I'm getting this "strobing" effect no matter the frame rate or resolution. Then I decided to try something different. I went and bought a mini-hdmi to hdmi cable and plugged the 7D directly into my hdtv. Hmm, no strobing at all. Nothing but silky smooth playback. So, apparently it's my computer. I have yet to render any 7d footage to a finished file or dvd... just been testing it in quicktime. I have the newest quad-core mac pro with 6gb of ram. So, would this be my processing power slowing me down, or the video card?

May 15th, 2010, 02:27 AM	#7
Manus Sweeney Major Player Join Date: May 2009 Location: Amsterdam, NL Posts: 217	strobing is usually a result of a clash in shutter speed/ framerate with certain types of artificial light.. Are you noticing the effect under the same light source always? Try experimenting with other shutter speeds and it should fix it, otherwise post a video and it should be possible to say what the source of the problem is.