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adrenalinestudios
03-02-2005, 02:28 PM
I guess you could say I am new to this game, I do a fair bit of compsiting work with footage from DV video, 16mm and 35mm film. So far everything I have done has been worked on at PAL 720x576 and either 4:3 or 16:9. So far I have yet to have any problems with this. But I have been trying to learn about a few things and have been getting a little confused. I need to know;

1. what is 2k and 4k and what pixel Width & Heights are they?
2. Is PAL resolution actually 720x576 or is it 768x576?
3. What is HD, is it just a larger resolution? What res is it actually?
4. When matte painting what sizes should my images be?
5. Are all of these different sizes 72dpi?

Please excuse my ignorance is this matter.

Aruna
03-02-2005, 05:45 PM
1. what is 2k and 4k and what pixel Width & Heights are they?

2K usually refers to 2048x1556 film frame. Different studios may use variations of this size, as some may scan this film frame in at a slightly higher 2K resolution. 4K is just double the 2K res, 4092x3112.


2. Is PAL resolution actually 720x576 or is it 768x576?

Not familiar with PAL, but I'd hazard a guess and say 720x576. Maybe someone in the PAL broadcasting industry will correct me.

3. What is HD, is it just a larger resolution? What res is it actually?

HD is a number of different sizes, but all of them have a pixel aspect of 1, and a frame aspect of 16x9. The resolutions are 480i, 480p, 720i, 720p, 1080i, 1080p. p stands for progressive, and i stands for interlaced. These are vertical resolutions.. To get the horizontal res, divide by nine and multiply by 16.

853x480
1280x720
1920x1080

4. When matte painting what sizes should my images be?

Depends on what your output resolution will be, and how detailed you want it.

5. Are all of these different sizes 72dpi?

72dpi is a print term. However, this number sometimes crops up when creating images in Photoshop or other image creation programs. You shouldn't care what dpi an image is at, since you'll be displaying pixels, not dots. You should care more about the final image size.

adrenalinestudios
03-02-2005, 11:22 PM
Ok great, thank you very much for that.

Is there a time when I should be using progressive scan rather than interlaced?

Also what exactly is Pan&Scan?

kiri
03-03-2005, 04:39 AM
Is there a time when I should be using progressive scan rather than interlaced?

I think that if you intend the output to be played on a computer you should use progressive as interlaced will result in a kind of blurring effect due to the way that monitors display video. Hopefully someone can provide a more detailed explanation.

Aruna
03-03-2005, 04:41 PM
Progressive displays every scanline sequentially, that is, it draws every frame at once. Interlaced displays odd/even scanlines sequentially, so it draws the odd fields (1,3,5,7,9,etc) first, then the even fields (2,4,6,8,10,etc). That's the simplied explanation (NTSC is actually backwards, it draws even, then odd).

You should always work in what your source materials have been shot at, and what your output medium will be.. If you're doing work for film, you'd create in frames. If you're doing stuff for broadcast and TV, you'd try to do your work in fields.

Pan & scan is a term used for films that have originally been shot for a widescreen, letterbox delivery, and displayed on TV screens full frame, effectively cutting off the left and right pieces of the film image. The term refers to a postproduction pan of the full film image so that the extreme left and right is viewable. It's pretty crappy to see widescreen films in pan & scan mode, since that is not what the director intended.

Google search for Pan & Scan (http://www.google.com/search?hl=en&lr=&safe=off&c2coff=1&q=pan+%26+scan&btnG=Search)

adrenalinestudios
03-03-2005, 11:36 PM
Thank you for your reply, thats all good know.
cheers.

Hugh
03-04-2005, 11:37 AM
Not familiar with PAL, but I'd hazard a guess and say 720x576. Maybe someone in the PAL broadcasting industry will correct me.


PAL is 720x576, with a pixel aspect ratio of 1.067

768x576 is "Square pixel PAL" - an old analogue capture card that I had many years ago used to capture at this resolution.... Although it's not proper PAL....

123mies
08-19-2005, 04:39 PM
PAL is 720x576, with a pixel aspect ratio of 1.067

768x576 is "Square pixel PAL" - an old analogue capture card that I had many years ago used to capture at this resolution.... Although it's not proper PAL....


Hi there,

When i export a quicktime movie out of a Avid symphony, it's size is going to be768x576. So why is this not a proper PAL format then?

Michel

Kai01W
08-19-2005, 05:23 PM
Hi there,
When i export a quicktime movie out of a Avid symphony, it's size is going to be768x576. So why is this not a proper PAL format then?
Michel
Well, unless I'm very mistaken the CCIR PAL standard is defined as 720x576 pixel. All the tape formats use this res. If you export at 768x576 it will look correct on a computer monitor but I guess you simply cannot output that res to any PAL VTR (unless the software/VTR automaticly resizes to 720).
I don't know AVID symphony but I guess you can also export at 720x576 pixel leaving the image untouched (I bet internally AVIDs work at 720 too).

-k

beaker
08-21-2005, 09:36 AM
Most of the highend avid systems work in a square aspect ratio and squish it at output. So for example NTSC on a Avid MC/Syphony is done at 720x540 and it squashes it to .9 at output. You video output actually looks better this way. Working in a non square aspect ratio causes rounding with can soften the video making it look crappy.

DreamingInDigital
08-22-2005, 05:45 AM
hi, to answer your question about the digital matte painting size...

you generaly always want the matte painting to be 2 times the resolution of you r final output. reasons for this are that maybe you want to move around in the matte a little. also it is alway better to have a bit of play room. maybe your matte needs to be camera mapped...like this you can move within the scene a little without it becomeing blurry the instant you move too close...

hope that this helps.......also anyone out there....correct me if i am wrong

Gemini82
08-24-2005, 07:07 PM
72dpi is a print term. However, this number sometimes crops up when creating images in Photoshop or other image creation programs. You shouldn't care what dpi an image is at, since you'll be displaying pixels, not dots. You should care more about the final image size.

Actually, you should care what the dpi is. The dpi directly correlates to file size. So if you where to have 300 dpi file versus a 72 dpi the file size will be larger on 300 dpi, more dots per square inch. It's good to stay at 72 for anything on the screen, normal screen resolution.
"since you'll be displaying pixels, not dots." thats not totally ture pixels are often referred to as dots. The reason why for print you would up the dpi is beacause of the transition form square to circle, (printers print in cirlces) it takes more "squares" to fill the print circles, thats why you up the dpi.

Aruna
08-24-2005, 07:31 PM
I don't really want to contribute to a thread that's been dead for at least five months, but....

Actually, you should care what the dpi is. The dpi directly correlates to file size. So if you where to have 300 dpi file versus a 72 dpi the file size will be larger on 300 dpi, more dots per square inch. It's good to stay at 72 for anything on the screen, normal screen resolution.

No. Not at all. If you're compositing for film/tv/broadcast, whatever, you don't need to care about dpi. The footage you receive is not in dpi. It's in defined pixel resolution (1280x720, 2048x1556, 720x486, etc). They are not listed as 1280x720 at 300dpi, or even 1280x720 at 72dpi. If you're not using photoshop, why care? Comp packages don't care what dpi your image is at, all they take are discrete pixel resolutions.


"since you'll be displaying pixels, not dots." thats not totally ture pixels are often referred to as dots. The reason why for print you would up the dpi is beacause of the transition form square to circle, (printers print in cirlces) it takes more "squares" to fill the print circles, thats why you up the dpi.

I've never referred to pixels as dots, and everyone I've talked too that works in compositing for visual effects doesn't refer to pixels as dots, or even uses them interchangeably. Print work and VFX work don't have too much in common. Of course, if you were to transfer a 2k frame for printing, you would have to deal with DPI, file resolution, CMYK, and all that. But if you're only in the film/tv/tape medium and you're delivering in that format, there's no need to hassle yourself with dpi.

From Dictionary.com
pixel - The basic unit of the composition of an image on a television screen, computer monitor, or similar display.

Pick up The Art and Science of Digital Compositing (http://www.amazon.com/exec/obidos/tg/detail/-/0121339602/qid=1124908200/sr=8-1/ref=pd_bbs_1/002-8636727-8233652?v=glance&s=books&n=507846). While six years old, it still contains quite a bit of valuable information that will help you with all your questions.

Gemini82
08-24-2005, 08:39 PM
Ok, but about the whole dot thing
From Dictionary.com
Dot: The basic unit of composition for an image produced by a device that prints text or graphics on paper: a resolution of 900 dots per inch.

Pixel: (computer science) the smallest discrete component of an image or picture on a CRT screen (usually a colored dot); "the greater the number of pixels per inch the grater the resolution"

It's my mistake for making the assumtion that it is a common accurance. Rethinking its probably best to differentiate the two terms, since they deal with two seperate forms of output. It is concievebale that dot and pixel could possibly be used interchangbly, because of their close association. (may it be right or wrong).


No. Not at all. If you're compositing for film/tv/broadcast, whatever, you don't need to care about dpi. The footage you receive is not in dpi. It's in defined pixel resolution (1280x720, 2048x1556, 720x486, etc). They are not listed as 1280x720 at 300dpi, or even 1280x720 at 72dpi. If you're not using photoshop, why care? Comp packages don't care what dpi your image is at, all they take are discrete pixel resolutions.

My Question is how is the dpi accounted for then? It may not be a convention to refer to footage you receive as 1280x720 at 300dpi, maybe because its an excepted standard for every to be a 72dpi (screen resolution). You dont refer constanly refer to a PC as a "Personal Computer with Harddrive, processor, and motherboard" because its commonly understood that they are standard components. Forgive me for being naive, but would'nt the dpi increase the file size, If you had 250 frames each frame at 300 dpi, meaning more dots per square inch.

P.S. Excuse my naiveness and spelling (not trying to be a know it all. I just want to understand)

Aruna
08-25-2005, 02:32 AM
The problem is that electronic image sequences don't have anything that relates to dpi. Electronic display mediums don't deal with dpi, as dpi is for print usage. When you acquire an image sequence off of DV tape, or film stock, or DVD, the images are in absolute terms, 720x486 for example. That's pixels

Print images in magazines and newspapers and the like have a variable thrown in, which is dpi. Some printers can print at 300dpi, or 600dpi (or even 1200 and 2400 dpi!). More dpi usually means more clarity in the picture. DPI does increase the file size, because there is more information that has to be shown in that square inch. So a 6"x8" image at 300dpi has more information and is a bigger file than one that is 6"x8" at 72dpi.

A little OT: How does a digital camera print images that can be so clear? Well, if a digital camera shoots 2048x1556 resolution images on it's CCD, that's 2048x1556 pixels. Doing a simple calculation, if it prints out a picture at 300dpi (like from one of those quick Canon easy print stations), 2048/300 and 1556/300 = 6.8"x5.1". Here, the dpi is interchanged with the pixel resolution (Because we're going out to the print medium). So theoretically our print image is that size, with a print resolution of 300dpi. Which is one of the reasons why blowing up a digital camera image to 10x12 or larger with a 2048x1556 image doesn't yield any more information (you'd need a 4096x3060 image to get the same quality, and even higher to get more information, but then you'd have to increase the dpi at that point). And of course, there's always some internal algorithms that the camera or printer makes to print a larger image. Usually the larger image just becomes softer.

While you can change the DPI in the print medium, you can't do that for electronic image sequences, since the display medium isn't print, it's video or film. That same 2048x1556 image that we shot on our digital camera is always going to be 2048x1556 in our electronic medium. So if we try to fit that 2048 image into our 720 frame, we lose everything above 720. We'll need to resize the image (which doesn't mean changing the dpi), it means scaling and resampling the image. So sometimes the 2k image will become soft and fuzzy, or sharp. At that point it depends on the filtering method, and that's a whole other story.

Hope that explains a little. I don't mean to jump at you.

mangolass
08-25-2005, 03:07 AM
Forgive me for being naive, but would'nt the dpi increase the file size, If you had 250 frames each frame at 300 dpi, meaning more dots per square inch.

It's really easy to understand if you try it yourself. Open any file in Adobe Photoshop, and choose "Image Size..."

Un~check the box at the bottom that says "Resample Image"

When resample Image is NOT checked, the number of pixels won't change.

Type in any number where it says "Resolution": 72, 300, whatever. Notice that this doesn't change the image at all. Save your file with whatever number you want there, it doesn't change file size. All it changes is the DPI setting for how magnified the image would be when printed.

If you think about the "per inch" thing, a DVD player doesn't even know how big your TV set is, so it can't do anything "per inch" ~ it only stores a certain number of pixels of detail and that gets displayed on any size TV.

HTH,

LT

Gemini82
08-25-2005, 03:37 AM
Clarity is so wonderful.

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