Aliasing only when screen size is small? at DVinfo.net

Go Back   DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon EOS Crop Sensor for HD

Canon EOS Crop Sensor for HD
APS-C sensor cameras including the 80D, 70D, 7D Mk. II, 7D, EOS M and Rebel models for HD video recording.


Reply
 
Thread Tools Search this Thread
Old October 26th, 2011, 01:46 AM   #1
Regular Crew
 
Join Date: Oct 2009
Location: new york
Posts: 94
Aliasing only when screen size is small?

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?
Alex Payne is offline   Reply With Quote
Old October 26th, 2011, 03:04 AM   #2
Regular Crew
 
Join Date: Oct 2009
Location: helsinki
Posts: 104
Re: Aliasing only when screen size is small?

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.
Mikko Topponen is offline   Reply With Quote
Old October 26th, 2011, 01:47 PM   #3
Regular Crew
 
Join Date: Oct 2009
Location: new york
Posts: 94
Re: Aliasing only when screen size is small?

Okay, so this is a dumb question, but how would I check the interlace settings on the original footage?
Alex Payne is offline   Reply With Quote
Old October 26th, 2011, 03:31 PM   #4
Trustee
 
Join Date: Oct 2009
Location: Mesa, AZ
Posts: 1,384
Re: Aliasing only when screen size is small?

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.
__________________
A7RII, C100, 1Dx, 5Dmk3, 70D, Kessler goodies, Adobe, Pro Tools and more!
Robert Turchick is offline   Reply With Quote
Old October 27th, 2011, 10:42 PM   #5
Trustee
 
Join Date: Jan 2008
Location: Mumbai, India
Posts: 1,385
Re: Aliasing only when screen size is small?

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.
__________________
Get the Free Comprehensive Guide to Rigging ANY Camera - one guide to rig them all - DSLRs to the Arri Alexa.
Sareesh Sudhakaran is offline   Reply With Quote
Old October 28th, 2011, 12:48 AM   #6
Regular Crew
 
Join Date: Oct 2009
Location: new york
Posts: 94
Re: Aliasing only when screen size is small?

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
Alex Payne is offline   Reply With Quote
Old October 28th, 2011, 04:54 AM   #7
Trustee
 
Join Date: Jan 2008
Location: Mumbai, India
Posts: 1,385
Re: Aliasing only when screen size is small?

Quote:
Originally Posted by Alex Payne View Post
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.
__________________
Get the Free Comprehensive Guide to Rigging ANY Camera - one guide to rig them all - DSLRs to the Arri Alexa.
Sareesh Sudhakaran is offline   Reply With Quote
Old October 28th, 2011, 03:03 PM   #8
Regular Crew
 
Join Date: Oct 2009
Location: new york
Posts: 94
Re: Aliasing only when screen size is small?

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)
Alex Payne is offline   Reply With Quote
Old October 29th, 2011, 09:03 AM   #9
Trustee
 
Join Date: Jan 2008
Location: Mumbai, India
Posts: 1,385
Re: Aliasing only when screen size is small?

Quote:
Originally Posted by Alex Payne View Post
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!
__________________
Get the Free Comprehensive Guide to Rigging ANY Camera - one guide to rig them all - DSLRs to the Arri Alexa.
Sareesh Sudhakaran is offline   Reply With Quote
Old November 1st, 2011, 09:07 AM   #10
Trustee
 
Join Date: Dec 2006
Location: Little Rock
Posts: 1,383
Re: Aliasing only when screen size is small?

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.
__________________
David W. Jones
www.joneshdfilms.com
David W. Jones is offline   Reply With Quote
Old November 1st, 2011, 01:38 PM   #11
Regular Crew
 
Join Date: Oct 2009
Location: helsinki
Posts: 104
Re: Aliasing only when screen size is small?

I've been using it for 5 years now. Especially it's scaling and interlacing capabilities are really bad.
Mikko Topponen is offline   Reply With Quote
Old November 1st, 2011, 01:40 PM   #12
Regular Crew
 
Join Date: Oct 2009
Location: helsinki
Posts: 104
Re: Aliasing only when screen size is small?

Quote:
Originally Posted by Alex Payne View Post
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.
Mikko Topponen is offline   Reply With Quote
Old November 1st, 2011, 07:25 PM   #13
Inner Circle
 
Join Date: Jan 2004
Location: Boca Raton, FL
Posts: 2,979
Re: Aliasing only when screen size is small?

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.
Les Wilson is offline   Reply With Quote
Old November 2nd, 2011, 12:01 PM   #14
Major Player
 
Join Date: Jun 2006
Location: Grand Rapids, MI
Posts: 233
Re: Aliasing only when screen size is small?

Quote:
Originally Posted by Sareesh Sudhakaran View Post
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.
__________________
always learning
www.phillippalacios.com
Phillip Palacios is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon EOS Crop Sensor for HD

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 09:42 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network