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png files appearing jagged
I don’t think I am setting my png files correctly in Illustrator for my video. I am using them in a video that I am rendering in HD. Any advice on how to properly set up my illustrator file and png exporting instructions?
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3 Replies
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It sounds like the resolution (i.e. number of pixels) is too low. I usually use a resolution which is about twice the resolution of the video. For example, if I want the png to be full screen for an NTSC video (720 pixels x 480 pixels), I will size the png as 1310 pixels x 960 pixels. If the image (the png in this case) does not have enough pixels, the software will add pixels to obtain a minimum resolution for display. This arbitrary addition of pixels can produce pixelation which yields things like jaggy lines.
Note that 1310 is not quite twice 720. I have found, by experimentation, that this resolution avoids letter boxing in Vegas.
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[Bob Peterson] “Note that 1310 is not quite twice 720. I have found, by experimentation, that this resolution avoids letter boxing in Vegas.”
It should be pointed out that NTSC video does not use square pixels. The pixel aspect ratio for NTSC SD is 0.9097. So the video is not 720, it is 720 x 0.9097 which is 654.984. Since you can’t have a fraction of a pixel you round this up to 655 giving you 655×480 square pixels. Therefore the correct dimension for doubling is 1310 as you said. No experimentation needed, just solid math! 😉 If you are using PAL the pixel aspect ratio should be different and if you are dealing with widescreen the pixel aspect ratio would be different again. You must use the correct pixel aspect ratio in the calculation.
~jr
http://www.johnrofrano.com
http://www.vasst.com -
Thanks John. I have never known the explanation although I did know that these dimensions avoid letter boxing. It did originally take me several tries to find the right dimension. Now, I know why it works.
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