Aliasing only when screen size is small?

[Alex Payne]

I thought I had a good handle on what would and wouldn't cause aliasing on the 7D, but I was thrown for a loop when I noticed a bit of jaggies on a shot from this weekend while editing in FCP... I go back and check the original footage, it's not there. I was stumped until I realized that if I took the original footage and shrunk it down to 1/5 size (or so), THAT'S when the jaggies appeared (which is why I saw it in the FCP viewer). What's up with that? Any way to fix it?

[Mikko Topponen]

If you take the viewer size down from 100% it will deinterlace causing jaggies. Just the viewer canvas though. If it's also in the file, check your interlace settings.

[Alex Payne]

Okay, so this is a dumb question, but how would I check the interlace settings on the original footage?

[Robert Turchick]

FCP... just have to learn how to use it. Correct that manually dragging a corner to resize the viewer window will yield a horrible image. Better to stick to the 100, 50, 25% presets which look fine.
Second, 7D shoots progressive. If you are importing the footage correctly your sequence will automatically set itself up for best results.

I transcode my 7D to pro res 422 via Mpeg Streamclip. Then drag it into a fresh sequence and you should get a message saying something to the effect "the sequence is not optimized for the footage, would you like to change to the proper settings". Click "yes" and everything will be fine.

[Sareesh Sudhakaran]

Moire is also produced by LCD screens - either on the back of the camera or your viewing monitor. If the moire vanishes when zoomed in it is not from the 7D.

[Alex Payne]

so why don't i notice it from other videos i watch on my laptop?
FCP really has nothing to do with it... it's a little strange, but yeah, anytime the window size of footage is too small, i'm getting moire in a lot of places... they disappear if i go to fullscreen. this is both in the original footage and the converted prores 422 files

[Sareesh Sudhakaran]

Originally Posted by Alex Payne

so why don't i notice it from other videos i watch on my laptop?

Possibly because they weren't shot with CMOS chip cameras. I see a lot of moire sometimes with crappy video. If you download resolution test charts that are above 100 lp/mm (supposedly the limit of LCD screens), you might see moire in action, even with your eyes. People prone to epileptic disorders are warned to not stare at these charts for long.

It's a very tough thing to control and reproduce - like lens flare, for instance. It's not anybody's fault, just a limitation of the technologies involved. That's why manufacturers with even millions of dollars to spare can't do anything better than throw in an AA filter (with different settings - they can't even agree among themselves) into the mix. Some just avoid it completely - like Leica for instance.

[Alex Payne]

so it IS from the 7D, is what you're getting at. Or at least, a result of shooting with the 7D. Anything I can do to avoid it in the future? Like I said, I'm generally pretty good at figuring out what will and won't cause it... but this seems to be happening with any small line (a pencil, for instance)

[Sareesh Sudhakaran]

Originally Posted by Alex Payne

Anything I can do to avoid it in the future?

If it is from the 7D (the most likely explanation), then you have no choice but to work around them. It is almost impossible to have a reliable degree of control over moire, even though various 'solutions' exist.

If this is something you can't avoid, switch to 3CCD cameras - they're still good!

[David W. Jones]

The monitor used to view footage on can have a dramatic effect on how the footage looks as well.
We did a test with the same footage playing on 7 different monitors. The original footage was very clean, but some monitors showed moire and aliasing in the footage and some did not.

[Mikko Topponen]

I've been using it for 5 years now. Especially it's scaling and interlacing capabilities are really bad.

[Mikko Topponen]

Originally Posted by Alex Payne

it's a little strange, but yeah, anytime the window size of footage is too small, i'm getting moire in a lot of places... they disappear if i go to fullscreen. this is both in the original footage and the converted prores 422 files

Change the program you are using to view the files.

[Les Wilson]

Aliasing happens in various circumstances when you scale images up and down. Many things go into it like the source material, the exact size you are resizing it to and the settings you are using in your software. What matters is how it looks when it's exported. If you want to learn and get better at the craft, do some searching, you'll find plenty of discussion on the topic.

[Phillip Palacios]

Originally Posted by Sareesh Sudhakaran

Possibly because they weren't shot with CMOS chip cameras. I see a lot of moire sometimes with crappy video. If you download resolution test charts that are above 100 lp/mm (supposedly the limit of LCD screens), you might see moire in action, even with your eyes. People prone to epileptic disorders are warned to not stare at these charts for long.

It's a very tough thing to control and reproduce - like lens flare, for instance. It's not anybody's fault, just a limitation of the technologies involved. That's why manufacturers with even millions of dollars to spare can't do anything better than throw in an AA filter (with different settings - they can't even agree among themselves) into the mix. Some just avoid it completely - like Leica for instance.

CMOS has nothing to do with it. Line skipping does.