-
Image quality degrades when switching 4:3 to Custom size canvas!!
Hi – I’ve been editing native 4:3 format footage that was imported from DV (16mm film that was transferred professionally to DV format) and I wanted to change the size of the canvas so that, upon export to quicktime/etc. the project would appear in 16:9 ratio. The problem is that, for no apparent reason, when I switch to a custom canvas size (in the Sequence Settings) and then rerender everything – all of a sudden a bunch of interlace-looking lines appear on everything (even after I export). I don’t understand why merely changing the canvas size would necessitate an image quality degredation or, for that matter, an imposition on the image itself at all (except for cropping). Does anyone know why this is happening and how I can get it to not happen?
-
4 Replies
-
[seth823] “for no apparent reason, when I switch to a custom canvas size (in the Sequence Settings) and then rerender everything – all of a sudden a bunch of interlace-looking lines appear on everything (even after I export).”
No surprise here.
Maintaining image-size/aspect, as captured, is a major factor to maintaining the highest quality finished image.
Changing the Canvas size can be very destructive to a video image when it requires pixel interpolation, reposition, expansion, and re-rendering to fit the adjusted aspect.For the best quality results, you can CROP the 4:3 to 16:9 letterbox (and if you reposition the image, make sure that the VERTICAL change is to an EVEN WHOLE number).
If you must “squeeze” the image, it would be better if you used the “aspect” control in the Motion Tab (under the Crop section) to “squeeze down” the vertical size and do not make any expansion of the horizontal aspect, nor do any repositioning vertically.
-
All I WAS trying to do was to crop the image. I changed the size from 720by480 pixels to 720by400 pixels – just chopping off the top and bottom. Even when the crop was the only shift, the interlacing thing is still a problem. I understand that stretching and expanding or even shrinking an image could result in a reinterpretation of the image (this happens with all digital media) but to merely crop off the top and bottom of an image and have the quality of the remaining image change is something that doesn’t make sense to me. What makes Final Cut different from Photoshop in this respect? Why would the program need to mess with the image instead of the process merely being subtractive? Is there a “smart” option that I can turn off to stop it from doing this?
I’m just a bit confused. Thanks, though, for the tips about vertical shifting and whatnot- I hadn’t considered that could be such a problem…
-
But in your first post you clearly stated that you created a “Custom Canvas Size” in the Sequence Settings.
This is not the same thing as using the “Crop” settings in the Motion Tab.A “crop” will not change the aspect of the video, it will only add black bars at the chosen edges of the image. The image will remain unaltered except for the “mask” that appears over it.
Custom Canvas Size can affect the actual aspect of the image and therefore degrade it.
-
Seth,
You don’t need to change the frame size in FCP, you change it your QuickTime Output Settings. Check out the article I wrote here:https://www.kenstone.net/fcp_homepage/understanding_16_9.html
Scroll to the bottom.
If you want to change the Canvas size, use a codec that can handle varying comp sizes, like the Animation codec. However, that is not the route you really want to go. I use varying comp sizes all the time in FCP. Usually for oversized sequences. For that I use Animation or Microcosm from Digital Anarchy.
Kevin Monahan
Take My FCP Master’s Seminar!
fcpworld.com
Reply to this Discussion! Login or Sign Up