Would cropping & using a wider aspect ratio help the gh1 codec?
- Thread starter Blackout
- Start date
iHartVideo
Well-known member
The GH1 uses a variable bit rate so I think you would just end up with a lower bit rate since there would be less 'real' data coming in.
Blackout
Veteran
I saw someone else who had a crop attachment thingy that went right on the lens, and masked the area to give a 2.39:1 frame. I had never seen it done that way and assumed everyone just cropped in a nle. I was wondering if since the codec wasn't having to deal with detail in the blocked area since it was just black, if it could give more resources to the area with actual picture information. We all know the 17mbit codec is pushing itself to the limit in 1080p mode.
It seems like it would be really easy to test this hypothesis. Shoot a shot with lots of motion that is repeatable. Do one take with a full image, then a second take with the top and bottom of the lens masked. Compare the results. I have to agree with Nitsuj that if you just mask the lens, the edges will blurry, and if you do it on the kit lens, any zooming is going to change the amount of "letterboxing" visible. The more you zoom in, the less of your masking will be visible.
Peter J. DeCrescenzo
Veteran
I raised this question several months ago, and Barry Green even tested it a bit, but it's problematic at best. A mask/matte mounted in front of the lens changes "size" and has blurry edges depending on the focal length of the lens:
http://www.dvxuser.com/V6/showthread.php?t=177178&highlight=matte
I corresponded with the folks at Hutech about the idea of making a high-precision metal mask/matte for the GH1 directly mounted _on_ the sensor to address these issues, but they decided there probably wasn't a big enough market to justify the costs. They make so-called "front filters" for astronomy applications which the user can insert & remove in their cameras directly behind the lens, but a matte/mask positioned like this would have the same sort of issues as one positioned in front of the lens:
http://www.sciencecenter.net/hutech/filters/ffilter.htm
They also sell modified DSLRs for astronomy applications:
http://www.hutech.com/AstroCamera.htm
http://www.dvxuser.com/V6/showthread.php?t=177178&highlight=matte
I corresponded with the folks at Hutech about the idea of making a high-precision metal mask/matte for the GH1 directly mounted _on_ the sensor to address these issues, but they decided there probably wasn't a big enough market to justify the costs. They make so-called "front filters" for astronomy applications which the user can insert & remove in their cameras directly behind the lens, but a matte/mask positioned like this would have the same sort of issues as one positioned in front of the lens:
http://www.sciencecenter.net/hutech/filters/ffilter.htm
They also sell modified DSLRs for astronomy applications:
http://www.hutech.com/AstroCamera.htm
Last edited:
TrueIndigo
Well-known member
Interesting idea, but does anyone know the answer to the original question? If you could use a mask would this "conserve" the datrate better for the letterboxed imagery or would it just turn down the quality since there would be slightly less changing imagery to compress because of the black masking?
Some thoughts:
Using a prime lens would not have the problem of variable focal lengths of a zoom lens with regard to the mask. A lens mask would be soft, but you could try less masking and then make the final sharp edge masking (to CinemaScope) in a NLE (though that would mean you would not get such a good saving on the codec -- if it works).
Some thoughts:
Using a prime lens would not have the problem of variable focal lengths of a zoom lens with regard to the mask. A lens mask would be soft, but you could try less masking and then make the final sharp edge masking (to CinemaScope) in a NLE (though that would mean you would not get such a good saving on the codec -- if it works).