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Quality concern at 480

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Martin Bolduc
Quality concern at 480
on Oct 9, 2009 at 3:24:17 pm

I shoot in 480p for the web. One told me that, since it uses only a small part of the CCD chips, the quality of the image would be better if I would shoot in 720 or even in 1080 and then downscale when rendering in Final Cut Pro. Does that make any sense?
Thanks,
martin


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Adam Smith
Re: Quality concern at 480
on Oct 10, 2009 at 8:10:43 pm

[Martin Bolduc] "since it uses only a small part of the CCD chips"

Ok, here's my take on the deal...

If you're shooting at Widescreen 16x9 then you are recording the whole image... all imaging is performed at 1080p and then downconverted to whatever format you are recording. Flip between 480/720/1080 and you will see all the same content on-screen (if you have SD set to 16x9).

Now if you prefer to shoot SD Letterbox then you truly do only wind up saving a portion of the image that your camera captured. But I'm not sure how much that affects quality…

Widescreen 16x9 is the original HD 16x9 image scaled down to 480 vertical resolution, then squeezed horizontally to fit everything into your 4x3 recording.

Side Crop takes the original 16x9 signal, scales it to 480 vertical like above, but it just ignores the sides of the image instead of scaling to fit. You lose some width on your shot.

Letterbox first Side Crops your shot, then places black bars over the picture, giving you a 16x9 shape - but this is not the full 16x9 image scaled to fit in 4x3 with matte, it's the camera cropping and covering your original image, only leaving a small window revealing a 16x9 shaped area.

So yes in some manner, shooting Side Crop or Letterbox is discarding some of the information from your imaging. But does that affect quality?

Both Widescreen and Side Crop have the full content vertically but Widescreen is squeezed horizontally, while Side Crop is squeezed vertically. There may be some minor difference in quality accounting for PAR but it sounds like a wash to me if you don't care about losing the sides.

Letterbox is the same image as Side Crop but with top and bottom obscured - so the image you wind up with has the same exact pixels and quality as Side Crop.

The only way I can think what your friend is saying makes sense, is if you preferred to shoot Letterbox… you could frame the shot in Letterbox with its reduced field of view, and then switch to Widescreen or HD (you now have a much wider shot) and zoom in to reframe the shot like you had before. This would capture that same scene using the full area of the image sensor and at higher resolution! The question is… if you need to deliver Letterboxed content, you're going to have to scale everything down to letterbox anyways… will you see any difference then?


- - -
Video Photographer / Avid & Final Cut Editor


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John Rosson
Re: Quality concern at 480
on Oct 16, 2009 at 8:12:22 pm

Martin,
Technical I am not -- but this may help you.
I thought compressing to the web was the great equalizer.
We use a Canon XL2 for much our content to the web.
Then we recently bought an HDX 900 -- for higher end production. My thinking was the web image would be much the same.
However, the HD image, compressed for the web (using 720/24p) looked significantly better to me.
Hope this helps.
JR


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Martin Bolduc
Re: Quality concern at 480
on Oct 16, 2009 at 10:37:14 pm

Thank you John,
I will test it when I'll have a minute.
Regards,
martin


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