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Old January 5th, 2009, 12:17 PM   #1
Mark Smith
 
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Image Resolution in pixels

Does anybody know if the resolution of a HD image is same as the resolution as SD footage?

Now before you go all stupid and critical of my silly question, I want to really know how many dots per inch or dots/pixels resolution 72 75 92 pixels etc

I will now ask again.

Are the pixel counts the same in both HD and SD?

in other words, Are the pixels the same in an SD image but more for an HD image?

Or should I ask it this way. If you had a given 1 inch square area on a HD TV screen, would an HD image have say for example 300 tv pixels in that 1 inch square area and an SD image would only have 72 for example?

I am not sure how to ask my question without confusing anybody, but maybe I have just made it worse lol

HELP!!!!!
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Old January 5th, 2009, 07:32 PM   #2
Trustee
 
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Location: North Conway, NH
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You've actually asked several questions and you seem to be trying to apply print metrics to video which absolutely do not apply for certain parameters. I'll answer as best I can.
Quote:
Originally Posted by Mark Smith View Post
Does anybody know if the resolution of a HD image is same as the resolution as SD footage?
No. If we're talking square pixels, full HD is 1920x1080. NTSC SD is 702x486, or something very close to that. PAL is a little larger than NTSC.

Quote:
Originally Posted by Mark Smith View Post
Now before you go all stupid and critical of my silly question, I want to really know how many dots per inch or dots/pixels resolution 72 75 92 pixels etc
Your computer monitor is probably 72dpi. Your video has no such representation. Dpi is a function of the display, not the video.

Quote:
Originally Posted by Mark Smith View Post
Are the pixel counts the same in both HD and SD?
in other words, Are the pixels the same in an SD image but more for an HD image?
No and yes. See the answer to the first question.

Quote:
Originally Posted by Mark Smith View Post
Or should I ask it this way. If you had a given 1 inch square area on a HD TV screen, would an HD image have say for example 300 tv pixels in that 1 inch square area and an SD image would only have 72 for example?
Again, that is a function of your TV screen, not your video. Full HD would be represented with 1080 lines of resolution on an HDTV that supports 1080. In the US, SD would be only 480 lines of visible resolution. That same TV would stretch the image across the entire screen by repeating every line roughly four times.

Quote:
Originally Posted by Mark Smith View Post
I am not sure how to ask my question without confusing anybody...
You might be confusing yourself most of all. (grin) Think of it this way. If you take a still picture with your digital camera and the picture is 3,000 pixels by 2,000 pixels, that is the resolution of your picture. When you print the picture, you can set it up for printing at 150dpi and your print will measure x by y. If you increase the image's dpi from 150 to 300, you printed pictures' size will now be 1/2x by 1/2y.

Those of us living in the world of digital video, both SD and HD, don't think in terms of dpi. We think in terms of horizontal resolution and vertical resolution. When we deal with images for video, like making something in Photoshop, it's always 72dpi because that's what video screens are.

HTH.
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Old January 7th, 2009, 08:39 PM   #3
Mark Smith
 
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Me now cured

Thanks for the info, I think I get it now.

HD verses SD = ratio of about 10 pixels for HD to 1 pixel for SD or something close but I think I am on the wright track now, thank you.

Last edited by Mark Smith; January 7th, 2009 at 08:43 PM. Reason: Spelling error lol
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Old January 8th, 2009, 01:34 AM   #4
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Join Date: Feb 2007
Location: Apple Valley CA
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Easy practical way to understand it... HD video is about 2x the number of lines, and about 4X the amount of data.

SD=480 lines from top to bottom of the screen (US, EU is 576?), and in widescreeen 720 lines from side to side...
HD=1080 (or sometimes 720) and somewere between 1440 and 1920 (not sure what the ratio is for 720...)

Toss in the 16:9 (i.e. 720x480) and 4:3 (640x480) differences and you get the general idea behind my first rough statement.

Hope that helps make it clearer from a layman's standpoint... don't think in terms of "pixels", think in terms of lines of resolution that a particular display/format allows for.

TVs typically have some teeny little chips that crunch the input, whatever its resolution, and decide how it ends up on the screen, whatever its resolution... and of course you're familiar with resolutions on computer monitors...

Cameras are a whole different discussion (try searching "pixel shifting" if you want to give yourself a headache) as you're dealing with sensor resolutions, and how the various manufactureres arrive at the stated output...
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