pixel aspect ratio question

[Darby Edelen]

[cathyralph] “My main concern is the that the bigger sizes will require bigger orignial drawings to be scanned-in – so I’m looking for the smallest option as I’m working with a 8.5 x 11.0”

I’m afraid I can’t answer your questions about HD as I haven’t started working with it yet, but I wouldn’t worry about the scanner. Most scanners are capable of ridiculously high DPI. So if you scan your image in at 8.5 x 11″ and 1440 DPI (probably excessive) you will have an image that is 12240 pixels x 15840 pixels and can then convert this to a 72 DPI image for video.

The size of your scanner’s bed only really matters in that you can’t scan anything physically larger than 8.5 x 11. But as long as your picture will fit on the scanner bed you should be able to scan it in at a resolution that will more than work for HD.

[Cathy Ralph]

Thanks – yes, adding DPI or PPI to the mix makes it even more confusing to me. I’ve been searching the net and see all different kinds of resolutions talked about. I just wish there were some definitive rule like “1920 x 1080, 300 dpi” that I could apply here. But thanks for your comment about the scanner – I’d forgotten that i could adjust for that.

[Steve Roberts]

Do 1920×1080. That way, if anyone wants 1280×720, you’re already set.

Now, regarding dpi: you want 1920×1080 pixels. DPI is PPI (the terms are interchangeable), which is pixels per inch.

To find the desired dpi for scanning, you shouldn’t look for a standard DPI, since there isn’t one for video work. DPI is only relevant when scanning print work to digital, or printing digital files to paper. When dealing with video, all you care about is pixel sizes such as 1920×1080.

But we need to convert the paper (inches) to pixels (digital file). The answer lies in the size of the paper image, and a bit of math.

If the paper were 16 inches by 9 inches, then to convert that to a digital file 1920×1080, we’d have to scan at this dpi: 1920pixels/16inches = 120 pixels/inch, or 120dpi.
You see? Digital pixels / paper size = scanning dpi.

Note that I conveniently chose a paper size which is 16×9 inches. In your case, you should only use part of your 11×8.5 page, so it matches the 16×9 HD ratio. So you should only use this portion of your page: 10.67×6.00 inches, or 11×6.1875 or thereabouts. Let’s say you were using the second one. Use the 11″ measurement to calculate the dpi:
1920pix/11 inches = 175 dpi approx.

If you have to choose a higher dpi, no big deal.

Does that make sense?

[Darby Edelen]

DPI shouldn’t come into the mix too much with video work, it’s something you only need to be concerned with when working in print… or scanning =)

As a general rule your assets for video work should be 72 DPI, but that doesn’t mean you have to (and you shouldn’t) scan them in at this DPI. When working with video you should be most concerned only with the number of pixels.

However, you can’t tell a scanner that you want a ‘1920 x 1080’ scan because scanners don’t know how big a pixel on a physical piece of paper is unless you tell them. That’s what DPI is effectively, it’s telling the scanner that every inch on the piece of paper corresponds to x pixels (where x is the DPI). So if you have an 8.5 x 11″ scan at 10 DPI you would end up with an 85 x 110 pixel scan (which would be pretty worthless).

You can’t get a perfect 1920 x 1080 pixel scan, as the aspect ratio isn’t equivalent to 8.5 x 11. But if you wanted to get close to a 1920 x 1080 pixel scan then you could divide 1920 by 11 and 1080 by 8.5 then make sure that you use a DPI setting at least as big as the larger number.

[Cathy Ralph]

Yes! I get it! Thank you so much for breaking this down for me. I’ve been posting this question in a zillion forums today and coming-up with nothing! Finally – an answer! 🙂 Thanks again.

[Cathy Ralph]

Thank you so much! I’ve been trying to find an answer to this all day! Now I finally “get it” ! 🙂 Thanks again.