Converting feet and inches to pixels

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Level 1

9 points

Converting feet and inches to pixels

I design Video Content for live shows. Often my set designer comes up with bizarre screen sizes. I am looking for a simple app that converts feet and inches into pixels. I want to be able to determine the pixel equivilent of his screen dimensions so that I can create a mask. I have done this using Photoshop, but it would be so much easier if I could simple input the dimensions and then get my results.

Here's a typical size he would give me...8' by 100 yards ( I know that's insane) or 37' by 17 '

Any help would be apprecitated

Mac Pro, Mac OS X (10.4.7)

Posted on Sep 7, 2006 10:28 AM

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Answer 1

Wes Plate

Level 4

2,859 points

Sep 7, 2006 10:38 AM in response to C Terrell

Depends on the resolution of your display(s), sorry.

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Answer 2

Sep 7, 2006 10:47 AM in response to C Terrell

Johnny,

Trust me ... I'm no mathematical wizard or technoguru, but it seems that as long as you know the aspect ratio of the screen you need to fill and you match that, the actual pixel dimensions would be more of a issue of the display device (a projector, I'm assuming).

For example, I output 720 x 480 (NTSC DV) to tape or 640 x 480 (DVD-Video) all the time that is later projected on a variety of different sized screens. If the screen is a 4:3 aspect ratio, my video fills the screen if the projector is positioned correctly and the right lens is used.

-DH

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Answer 3

C Terrell Author

Level 1

9 points

Sep 7, 2006 11:10 AM in response to David Harbsmeier

Johnny,

Trust me ... I'm no mathematical wizard or
technoguru, but it seems that as long as you know the
aspect ratio of the screen you need to fill and you
match that, the actual pixel dimensions would be more
of a issue of the display device (a projector, I'm
assuming).

For example, I output 720 x 480 (NTSC DV) to tape or
640 x 480 (DVD-Video) all the time that is later
projected on a variety of different sized screens.
If the screen is a 4:3 aspect ratio, my video fills
the screen if the projector is positioned correctly
and the right lens is used.

-DH

Thanks for the replies guys.
The problem is that he never gives me ratios, he just gives me stratight sizes.
I build these in 720 x 480 and they are sent through some unexplicable beta/do-ray-me configuration to output on giant LED walls. The resolution doesn't matter. This strange output configuration only reads my video the same as if I was outputting straight from FCP.

On one job he gave me the simple 16:9 ratio and I simply put a 16:9 matte on everything within a 720 x 480 using Joe's Filter Beta "Joe’s Aspect Matte RT".
That was easy. What gets tricky is when he gives me some strange size like
37 feet high by 6 feet wide. Is there an easy way to figure out this ratio and then build it within 720 x 480 using a matte. If I knew the pixel numbers of 37' by 6' I could just adjust my matte accordingly.

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Answer 4

Sep 7, 2006 11:51 AM in response to C Terrell

If I knew the pixel numbers of 37' by 6' I could just adjust my matte accordingly. < </div>

You are confusing terms from the print world and trying to make them work in video. Pixels are just the smallest picture elements. A 640x480 pixel-based image can be ten inches or high pr it can be ten feet high. The number of pixels never changes, only the size of the pixels.

If your goofball "designer" wants an image that is 37 by 6 feet your aspect ratio is simple math: 37 divided by 6 is 6.17. That's all you can know about the format. Your display's resolution must be known. Let's say it's 640x480. If the 640 is the 37 feet, you'll reduce the 480 by a factor of 6.17 to umm, heck you do the math.

There is no direct correlation between pixels and linear measurements. The number of pixels in your display cannot change. The only things that change are whether or not some pixels are used (or masked off and therefore unused) or the size of the pixels being displayed. That is, if you're placing a 640x480 image onto a 1280x960 screen, each of the original pixels will be four times as large as the ones you created. If you try to place a 1280x960 image on a 640x480 display, only one fourth of the image, 25% of the pixels, will be visible or, if the image is scaled down to fit, 75% of your pixels will be thrown away.

bogiesan

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Answer 5

C Terrell Author

Level 1

9 points

Sep 7, 2006 12:12 PM in response to David Bogie Chq-1

Ok, let me try to illustrate my problem...

Lets say that this is my original content. A clip of a hot girl and a car.

http://homepage.mac.com/charlieterrell/PhotoAlbum76.html

But I have to fit it on a screen that is like the example of Girl 2

Notice I had to move the girl to the center so that it will read properly on the
long tall LED wall. I put a matte on the image so that while I'm working I can
design the content accordingly.

But...how do I simply determine the size of my matte. Should 37' by 6' be the matte in example 2 or example 3?

I did random matte sizes just to illustrate my question, but if you were given this problem how would you determine how much black matte to put on your clips in order to acheive the right ratio for output?

Thanks for your help guys. It's just the math thing. It makes me crazy.

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Answer 6

Sep 7, 2006 12:52 PM in response to C Terrell

Okay, maybe I'm totally misreading this, but it sounds like simple math.

37' wide by 6' high comes out to 720 pix wide x 117 pix high.

(With is the wider of the 2 so I took (720x6)/37=~117

Go into Photoshop, make a 720x480 black background and cut a 720x117 hole out of it and export. There's your matte. (You could probably use those numbers to make a matte in FCP by using crop).

Does this work, or did I miss the point?

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Answer 7

Sep 7, 2006 1:10 PM in response to Jake Abramson

Okay, more carefull re-reading your post I see you're trying to figure out how to do it in FCP.

I'm not sure of exactly how to do the math of the last step, but you need to find what percent to use for the crop tool. I keep coming up with 25% off the top and botom but that isn't right ... Any math wizards want to chime in?

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Answer 8

Sep 7, 2006 1:46 PM in response to Jake Abramson

You guys are making this more difficult than it needs to be but I'm trying to make it simpler than it can be in real life.

Open Photoshop. Build a rectangular object that is 37 units by 6 units. The "units" don't matter in the slightest, could be pixels or tens of pixels or grapefruits. Import his into FCP. Making sure you have the correct pixel aspect ration (I cannot help you there, I deeply loathe Photoshop), constrain and scale your object until it fits inside the edges of your chosen FCP sequence format.

End of problem.

I'd use After Effects to get a perfectly scaled matte object.

bogiesan

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