Proper Resizing of Stills

[John Rofrano]

PPI is irrelevant to video. It is a print measurement. The rule of thumb for video is to double the output resolution if you plan to pan and zoom the image. Otheriwse use the output resolution. Since an NTSC DVD will have 655×480 square pixels you should use 1310×960 if you pan to zoom into the image at all. Some people don’t take the square pixels into account and double 720×480 to 1440×480. That’s acceptable too.

Remember DVD video is only 655×480 and 655×480 = 314,400 pixels. That’s 0.3 mega pixels! So you are correct that giving Vegas a 10 MP image and asking it to resize it to 0.3 MP is asking a lot. Do that in a dedicate image editor with a bicubic resize as you were planning.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[John Gregoriades]

Thank you, John
Your reply was very helpful.
I did some testing (don’t know how valid it was.) Took an original picture 368×2736 (10MP) and using Paintshop Pro resized it at two levels: 75% and 50% (2736×2052 and 1824×1368) maintaining its native 180ppi. (Note the 50% reduction results in dimensions which are 16% greater than the rule of thumb of twice the video resolution of 1574×1152 for PAL.)
I rendered all three in-a-row on the timeline to MPG2 via Vegas, and played the result back on Windows Media Player.
The original (10MP) was over-digitized, jaggies etc. present. The 75% had smoothed out the jaggies, and was the best looking. The 50% was still good, but had started losing some of the sharpness in comparison to the 75%.
Do you think that a 2736×2052 (5.6 MP) pic – which is 3.5 times the horizontal dimension of the PAL video, too much for Vegas? Would the rendering take a significantly longer time? Any other problems to worry about?
Thank you again.

John23GR

[John Rofrano]

The larger size will take more memory and longer to render because Vegas still has to scale it but if it’s the best to your eyes then I say go for it. In the end, you gotta be happy with what you produce.

If your project takes too long to render or you start running out of resources while editing then cut the size down a bit more. HD is 1920×1080 so you might try resizing them to HD size which we know Vegas handles well.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[John Gregoriades]

Thank you, John.
Your suggestion about using 1920×1080 is something I can follow. But I have each leg in different worlds: Both NTSC and PAL, and am wondring if HD is the same on both, or do these continue to have the NTSC and PAL distinction. If there is still a distinction, what would be the HD equivalent for PAL?
The other issue is that if the present photos on a 1.33 ratio, are resampled into the 1.78 ratio you suggest, how would that work? I imagine that one would resample for the height (1080) maintaining the original width/heighth ratio, and the result by Vegas would be black (letterbox) on either side of the wide screen?

John23GR

[John Rofrano]

> But I have each leg in different worlds: Both NTSC and PAL, and am wondring if HD is the same on both, or do these continue to have the NTSC and PAL distinction.

HD is the same for NTSC and PAL. Only the frame rates are different.

> The other issue is that if the present photos on a 1.33 ratio, are resampled into the 1.78 ratio you suggest, how would that work?

I don’t remember suggesting a 1.78 ratio? What makes you think that your Canon A620 shoots with a 1.3333 aspect ratio? I’ve never heard of this. All digital cameras shoot with a PAR of 1.0. Only camcorders have a notion of non square pixels because that is a video concept. Only recently have photo editors like Photoshop added view compensation for images coming from video with non-square pixels but regular photo cameras all shoot square pixels.

> I imagine that one would resample for the height (1080) maintaining the original width/heighth ratio, and the result by Vegas would be black (letterbox) on either side of the wide screen?

Actually just the opposite. Non-square pixels only affect the width. If you needed to compensate you would resize the width of the image to make it square again.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[John Gregoriades]

Many thanks, again, John. You have provided me with excellent guidance and I’ve already produced an acceptable quality DVD. (Especially sharp when viewed in one of the new flat-screen 32″ TVs last nite.)
Just to clarify my confusion, you asked what made me think that the Canon A620 photos are at 1.33 ratio. That comes from the photos being 3072×2304 pixels, which the W divided by the H = 1.3333 or a 4:3 ratio). Vegas uses (for NTSC) 654×480 which is a 1.3625 ratio, in other words the latter is slightly “flatter” than the cam’s photo. This results in a very tiny amount of black vertical stripes on either side of the video. Vegas appears to be designed to “give the max full picture it can,” and letterbox either horizontally or vertically, to avoid cropping, if the photo’s ratio is not a match for its 654×480. (An excellent design.)
I misunderstood what you meant by HD’s ratio. Dividing 1920 by 1080 gives 1.777 ratio, which of course is the new, wide-aspect screen. Obviously, resampling a 1.333 photo at that particular (approx 9:5) ratio would give the photo an undesirable stretched look. But resampling them at 1920×1440 cuts down the original size, keeps acceptable quality, and maintains the 1.333 ratio.
I think I “got it” and many thanks again!
John

John23GR

[John Rofrano]

OK, that was my error for mistaking your “Pixel Ratio” for “Pixel Aspect Ratio”. We were talking about two different things because I made a bad assumption (sorry). I agree, I think you’ve got it now. 😉

~jr

http://www.johnrofrano.com
http://www.vasst.com