NTSC>PAL via Photoshop?

[MovieStuff]

Okay, been doin' some experimentin' via long distance with Scot McPhie downunder. I sent him some footage from the DV8 for him to put on his timeline to see what it would look like. I thought about the whole PAL vs NTSC aspect ratio problem and here is the solution I came up with:

I took about 25 frames of my full frame NTSC DV8 transfers and exported them as a numbered JPEG sequence. Now, at this point, the aspect ratio for the NTSC is 720x486. If I just sent that to Scot, it would looked stretched on his 720x576 PAL system. So, I batched processed the frames in Photoshop, expanding the canvas height out to 576 from the original 486. By expanding the canvas, the image stayed the original aspect ratio and black was merely added top and bottom in a sort of letter box effect. If this works, it means I might be able to transfer film one to one for 25fps playback on PAL. However, it would be limited to letterboxed transfers only, where the entire NTSC frame floats between black bands at the top and bottom. In all, not a bad looking effect, actually.

I haven't heard back from Scot. It's really funny. His time zone and mine are like 180 degrees different. In the mornings I get a call where he's just getting ready to go to bed. Then later that SAME afternoon, he calls me up to tell me that he just got up from sleeping all night and has a brainstorm! My morning is his evening and my evening is his morning. Crazy.

Anyway, we're attempting to work together on some special effects for his groovy film. I haven't heard how the clips I sent him over the net worked out.

Roger

[TA152]

Why do you not simply resize it to the "standard" PAL format of 768x576 (4:3) or simply choose one that conforms to whatever (4x:3y) the NTSC really is?

Some "tweaking" (off 4:3) will not be visible.

I believe that it is much simpler to do this "tweak" in Adobe Premiere, isn?t it?

R

[MovieStuff]

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">Originally posted by S8 Booster:
Why do you not simply resize it to the "standard" PAL format of 768x576
I believe that it is much simpler to do this "tweak" in Adobe Premiere, isn?t it?</font></td></tr></table></td></tr></table></BLOCKQUOTE>

I have no such function in my version of Premier 5.1c, which is the highest I can use with my particular Pinnacle Board. However, I think that doing so would sacrifice considerable resolution as it would stretch the vertical height of the NTSC video to the height of the PAL video and would also lose valuable information off the sides. There is also the difference in pixel shape between PAL and NTSC to consider. The way I've done it *appears* to avoid both those issues but, again, I have not heard back from Scot so I don't really know.

Scot, are you out there? Well, I know you're "out there". What I mean is, are you reading this? [img]smile.gif[/img]

Roger

[TA152]

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">There is also the difference in pixel shape between PAL and NTSC to consider. The way I've done it *appears* to avoid both those issues but, again, I have not heard back from Scot so I don't really know. </font></td></tr></table></td></tr></table></BLOCKQUOTE>

If you can still not get hold of Scot and are interested you can post a short film "reel" at your site so I can download it and do some format tests in Adobe Premiere with it.

R

[Scotness]

Yes I am here (out there!) - a virus got to my computer and even forced me to set a new profile here (by virtue the clean up programme killing an email with my new old password (if you know what I mean....hmm out there)).....anyway (I've already emailed Roger but just to put it here too) -- the test was quite succesful -- the only thing was I couldn't import them as a numbered sequence of stills (so did each individually) and it wouldn't play off the timeline - so I rendered them as an avi and it played fine -- perhaps both of these problems were caused because the stills were jpegs, or because I didn't know enough about it -- but the end result was fine -- and the aspect ratio was right with the black bars at the top and bottom, which explains why Lost Tribes had that when I played it off my VCR (which can play NTSC or PAL). It's actually a nice ratio I think - it's sort of widish (kind of) -- so anyway it was all successful.

[mattias]

you shouldn't expand the canvas, but simply stretch the images to the correct height as suggested. to be exact, you should probably resample the image to 702x576 and expand the canvas to 720x576 to take care of all the pixel aspect issues, but simply resizing to 720x576 is easier and close enough. make sure you set the aspect ratio of the images/clip to pal (5:4) though, or your nls might want to do the stretching again. a better/easier way might be to scale the ntsc footage to 768x576, set it to square pixels and let the nle do the rest. fcp handles this just fine, and probably premiere as well. if you're using dv, you should add the missing 6 lines first, and remember to add two at the top and four at the bottom if you want to keep the field order intact.

/matt

[MovieStuff]

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">Originally posted by mattias:
you shouldn't expand the canvas, but simply stretch the images to the correct height as suggested.</font></td></tr></table></td></tr></table></BLOCKQUOTE>

I tried that and two things happened:

1) I lost considerable information on the left and right edges; too much considering that I had ALREADY given up information on the left and right during the initial transfer to NTSC since the aspect ratio of super 8 and NTSC are not the same.

2) By stretching the height of the 486 to 576, there was a considerable and noticable loss of perceptual resolution. By that I mean that the math might work out okay but the end result simply looked ragged.

By keeping the image centered within the PAL frame, the original number of lines are still present in the NTSC image but the picture merely "floats" in the middle of the PAL image, with the excess PAL lines making up the black at the top and bottom. I don't lose any of the original NTSC image and the resolution is exactly the same as if were viewed on an NTSC monitor.

Seems like a win-win situation to me unless one doesn't want the "letter-boxed" look that results. Blowing it up to the height of a PAL frame won't increase the resolution of the NTSC frame and, from I've seen, actually adds certain artifacts to the image that I find undesirable (the aforementioned "ragged edges" or aliasing. Floating the image seems to avoid those problems and maintains all the information in the original NTSC frame without losing anything on the sides.

Roger

<font color="#a62a2a" size="1">[ August 24, 2002 10:47 AM: Message edited by: MovieStuff ]</font>

[mattias]

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">1) I lost considerable information on the left and right edges; too much considering that I had ALREADY given up information on the left and right during the initial transfer to NTSC since the aspect ratio of super 8 and NTSC are not the same.</font></td></tr></table></td></tr></table></BLOCKQUOTE>
it's actually the other way around. to convert ntsc to pal resolution, you should only stretch the image vertically, since the horizontal resolution is the same. it's when you *don't* stretch that you lose information (resolution) since you have to squeeze the image horizontally instead to get the correct aspect ratio.
<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">2) By stretching the height of the 486 to 576, there was a considerable and noticable loss of perceptual resolution.</font></td></tr></table></td></tr></table></BLOCKQUOTE>
of course. that's why ntsc always looks soft when transferred to pal. there's really no way of avoiding this since the resolution is in fact lower...
<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">By keeping the image centered within the PAL frame, the original number of lines are still present in the NTSC image but the picture merely "floats" in the middle of the PAL image, with the excess PAL lines making up the black at the top and bottom. I don't lose any of the original NTSC image and the resolution is exactly the same as if were viewed on an NTSC monitor. </font></td></tr></table></td></tr></table></BLOCKQUOTE>
true, but the aspect ratio will be off when viewed on a pal monitor. the picture aspect ratio of ntsc is the same as in pal, but the *pixel* aspect ratio is different. ntsc looks wide on a square pixel monitor (since a ntsc monitor has tall pixels), while pal looks tall (since a pal monitor has wide pixels). converting a ntsc image to pal without stretching it vertically will make it look even wider. you really should try to get hold of a pal monitor. it's the only way of really understanding what i'm talking about...

/matt

<font color="#a62a2a" size="1">[ August 26, 2002 10:25 AM: Message edited by: mattias ]</font>

[MovieStuff]

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">Originally posted by mattias:

true, but the aspect ratio will be off when viewed on a pal monitor. the picture aspect ratio of ntsc is the same as in pal, but the *pixel* aspect ratio is different. </font></td></tr></table></td></tr></table></BLOCKQUOTE>

I understand what you are saying about the difference between the aspect ratios of PAL and NTSC's pixels. However, what I'm NOT clear about is this: Are the pixels in Photoshop the same as NTSC or PAL? If I capture a bit map file in NTSC and open it in Photoshop, does Photoshop "take on" the pixel shape of NTSC? If so, does it also do the same for a PAL bit map still frame? And what if I combine the two images (PAL and NTSC) together on the same canvas?

The confusing part is that, if what you are saying is true, then changing the height of the NTSC frame in Photoshop to match PAL won't make any difference since the height in Photoshop is still being determined by pixels that don't match the shape of PAL pixels. In other words, the number of pixels will be the same but the shape of objects within the image will look distorted. It would seem to me that if what you are saying will work, then "floating" the NTSC image in the middle of the very same canvas size will also work and preserve the correct aspect ratio of the original NTSC image. I don't see how changing the height of the NTSC image can work with the very same type of pixels that WON'T work when "floating" the image like I described.

Again, are Photoshop pixels different than NTSC or PAL? And if they are, then what happens when either an NTSC or PAL bit map image is opened in Photoshop and the image manipulated? Does Photoshop intermix different pixel shapes within the same image?

I've done a lot of Photoshop work but I've never really considered things at the pixel level so I'm learing something new here (assuming someone really knows the answer!).

Roger

[blackangus1]

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">Originally posted by MovieStuff:


However, what I'm NOT clear about is this: Are the pixels in Photoshop the same as NTSC or PAL?
Roger</font></td></tr></table></td></tr></table></BLOCKQUOTE>

No. Photoshop expects to be operating in the realm of "square" pixels, where each pixel is the same height as it is width. This is usually accomplished using a 4:3 display and a 4:3 resolution on your display (such as 800x600, or 1024x768).

NTSC pixels are taller than they are wide. PAL pixels are wider than they are tall.

If you take video of a perfect circle on a DV NTSC camera, and import it into photoshop, the image displayed will be an oval, somewhat squashed down top-to-bottom and stretched out side-to-side. The reason is, Photoshop is using its square pixels to interpret an image that was captured using tall/skinny pixels. So, the square pixels stretch out the width, since they are wider than the NTSC pixels.

If you took video of that same perfect circle on a DV PAL camera and imported a frame of it into Photoshop, the display would look like a slightly thinner/taller oval. It wouldn't be perfectly round, it'd be an oval that looked like it was squished in on the sides a bit.

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">Originally posted by MovieStuff:

If I capture a bit map file in NTSC and open it in Photoshop, does Photoshop "take on" the pixel shape of NTSC?
Roger</font></td></tr></table></td></tr></table></BLOCKQUOTE>

No. See above. It would use wider "square" pixels to display the image, which was intended to be viewed in narrower "tall" pixels. The result will look stretched-out horizontally. Same for PAL (but in reverse).

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">Originally posted by MovieStuff:

And what if I combine the two images (PAL and NTSC) together on the same canvas?
Roger</font></td></tr></table></td></tr></table></BLOCKQUOTE>

Ah - then you would have a "mess". [img]smile.gif[/img]

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">Originally posted by MovieStuff:


The confusing part is that, if what you are saying is true, then changing the height of the NTSC frame in Photoshop to match PAL won't make any difference since the height in Photoshop is still being determined by pixels that don't match the shape of PAL pixels.
Roger</font></td></tr></table></td></tr></table></BLOCKQUOTE>

No, it will fix it. See, the image is intended to look 4:3 on all the displays -- PAL is 4:3, NTSC is 4:3, and computer displays (Photoshop) are 4:3. So everybody wants the object to look the same. The difference is in the shape of the pixels, and the way you counteract that is by changing the number of pixels to match the shape.

So, if you took a square-pixel image from a computer... say, make a 640x480 canvas, and draw a perfect circle in it. That image has an aspect ratio of 4:3 (based on the pixel count) and it looks proper on the computer display because the computer uses 1:1 pixels.

If you want to display that image so it looks proper on NTSC, you'd have to stretch the canvas to 720x480. It will now look wrong on the computer, but it will look right on the TV. It will have an aspect ratio of 1.5:1 based on pixel count, but it still clocks in at 1.33:1 because the pixels aren't square, they're skinny, so it takes more of them to make up a line.

If you want the original image to look right on PAL, you'd have to stretch it to 720x576. Again, it would look wrong on the computer, but it will look right on the PAL display. It's 1.25:1 by pixel count, but the pixel shape of the PAL display will squash it down so it looks 4:3 on the PAL display.