How do I record a computer monitor without banding/flickering with a Canon t2i/550D?

Question

As you've probably guessed, when recording video with a computer monitor in frame I am getting banding. I'm aware that this has to do with refresh rates of the monitor vs the scan rate of the camera or something like that. I've read that most cameras have a feature to adjust for this - synchro scan, clear scan or variable scan is what I've seen it referred to as. However, I can't find anything on what or how to do this with my Canon t2i.

I've seen a number of videos where people do this with a t2i, so I'm sure it's possible, I'm just not sure how to set the camera up properly.

Here is a video using a t2i to record a computer screen without banding.

I've noticed that I can adjust f/stop and shutter speed to get varying results when put in to Tv mode. I'm having trouble getting to a setting that has minimal/no banding and isn't either under or over exposed.

Answer 1

While reviewing the Instruction Manual for the Canon 2Ti EOS 550 on page 127 you will find information on how to manually set the shutter time. Here is the pdf download for the manual: http://gdlp01.c-wss.com/gds/9/0300003169/01/eosrt2i-eos550d-im-en.pdf

There is wide range of 1/4000 to 1/30 of a second to work with depending on your frame rate.

For 50 fps or 60 fps the range is 1/4000 to 1/60.

For 24, 25, & 30 fps the range is 1/4000 to 1/30.

I suggest that you try different shutter times at your preferred frame rate. I know this is not definitive, as I don't have this camera, nor have I tested this. However, the flicker you are referring to is as you suggest a synchronization issue; you are trying to have the camera capture at a rate that synchronizes with the display. Another thing you can try is change the display frame rate, if you have this option on your monitor.

Hope this helps,

Answer 2

The link on the video says they used magic lantern which is alternate firmware update that is open source for the t2i and other canon bodies. I can only say that canon will not support it, it can void your warrenty, and overheat and cause all sorts of shut down problems. Having said that, this is how they were able to adjust the shutter setting slower. I have also seen some amazingly high speed slow mo stuff shot progressive speed ramped to look like arri alexa. Amazing.

Here is my take on it, I am a pro video with 18 years of broadcast. Personally I would not try ML on my t2i until I get a better camera and this guy becomes no issue for me as a backup body. The issue with these canon cameras as video cameras lies in the fact that the processor used to backhaul the data is not optimized for video, it is optimized for great stills, stunning in fact. Video processing although lower res even on 1080 i/p, uses a lot of processing, even more than just getting a 18mp still on raw with AA. Its not even in the same ball park. Processing is heat, and this camera and other canon bodies can overheat even on the regular f/w let alone some of the crazy thing ML will let you do. This is why video has lagged behind film in quality and why a C300 or C500 is thousands of dollars more for a dedicated canon video camera.

Personally I really give magic lantern a lot of credit, they essentially overhauled the system software to give you zebra bars, markers, better shutter, intervolometer etc. I am just not about to try it on my cam since it is still my primary.

For people out there needing a low light solution, check out a EF 1.4 or 1.2 manual focus 50mm lens, it is some of the best glass canon ever made and edge to edge sharp.

Answer 3

just figured it out woth magic lantern. You wanna turn on frame rate override, and change thr timing clock from its perfect number to something slightly above or below the usual 4200 or whatever it is. I got a true frame rate of 26.007, and a flicker free video of a lcd screen. Bam!

Answer 4

Hey I know this is an old post, but I have been trying to figure this out definitively.

My situation is thus. I am using a T2i, except I am trying to record from my projector, an inFocus IN104 (it was basically the cheapest I could afford at the time).

I have tried a bunch of lenses (kit lens 18 - 55mm (3.5 - 5.6), Pentax 50mm (1.7), Pentax 135mm(3.5)) at all f stop values and on the camera all the ISO values, all the shutter speeds, all the frame rates. I have tried to adjust the projector "Phase" value which the manual is a bit unclear about...but doesn't seem to effect the bars.

The only thing that really seems to effect the rolling bars is the shutter speed on the camera. I turn the shutter speed all the way down to 30 (It will only go to 60 at 60fps), I know these aren't the "recommended" settings, but I only really notice different ISO settings when they are higher and it looks like a Jason Bourne fight scene (ie less natural motion blur).

This itself will NOT eliminate the bars. The next thing you will have to do, I find if I just turn the camera on and off a couple times it will magically "sync up" and there will be no bars and sometimes they will be slightly visible.

Also this will depend on the content you are recording. I am using the projector to project an animation I did which is largely solid colors on a black field and it is VERY noticable. If you had say, a bunch of people talking and moving around on a dark background it would be less noticable...though you'd probably just actually film that scene.

hope this helps.