Why did the filter -enhanced lighting- reduce file size?

Doug2006 · Post by **Doug2006** » Wed Mar 21, 2007 1:32 am

I took a small 36 minute clip and used the enhance lighting filter to try and lighten it up. It worked but I noticed that the file size went from 1.3 gig to 976 megs. It looks fine and is the same length and number of frames. Is this something I should be concerned about or what? And if not then wouldn't it make sense to run everything through the enhanced filter?
Doug

heinz-oz · Post by **heinz-oz** » Wed Mar 21, 2007 3:12 am

I take it that your source file was mpeg2, right?

By applying a filter and rendering it out, the mpeg2 compression was applied again, reducing the file size. Smaller file sizes mean discarded information. Mpeg compression, as we all know, is lossy.

Yes, you should be concerned about it because this will happen every time you render your clip again. Doing it often enough you will end up with dismal video quality. If you work with mpeg files to start with, this cannot be avoided but you should not render the clip until all your editing is done to reduce losses.

Doug2006 · Post by **Doug2006** » Wed Mar 21, 2007 5:29 am

Ok, Thanks for the reply.

daniel · Post by **daniel** » Wed Mar 21, 2007 12:53 pm

I remain curious anyway about the importance of the recompression.
36 min for 1.6GB is roughly 6MB/s.
That's rather reasonable quality so the loss should not be so large.

Are you sure you re-used the same settings and that the corrected video is the same properties as the original?
Was the quality setting at the default 70 or around 100?
How much was the filter correction? Did it bring out significant noise in the clip by heavy brightening of dark areas??

I'm surprised that re-encoding at 6MB would throw away 25% of the size...