Aspect Ratio Differences - PS and VV

CVM wrote on 11/10/2007, 3:14 PM
Can someone explain why, when I create a 720x480 still image in PhotoShop and then import it into Vegas (SD DV project), the image appears in the preview window smaller? I am left with horizontal black bars on the top and bottom.

Certainly, I can eliminate the black bars by un-selecting 'Match Aspect Ratio' in the image's sub-menu, but then the image is stretched vertically a bit (I have to do this when I import a JumpBack, but the resulting 'stretched' image is not offensive... where the 'stretched' PhotoShop image is).

I assumed if I create a 720x480 image in PhotoShop and import it into an SD project (DV) in Vegas, it would fit perfectly. Does anyone know why it doesn't? And, more importanly, what is the pixel size I need to use in PhotoShop to make it fit in Vegas?

Thanks.

Comments

John_Cline wrote on 11/10/2007, 3:22 PM
Make your images 720x540. Photoshop deals with images using a square pixel format, DV is a rectangular pixel format.
rmack350 wrote on 11/10/2007, 4:19 PM
720x528.
rmack350 wrote on 11/10/2007, 4:51 PM
Explain why...

Vegas assumes all still images have a "square" pixel aspect ratio and so it resamples them to fit into and match your project. So, for an NTSC DV project Vegas will adjust the PAR of your image and then resize it to fit into the frame.

It's not obvious that Vegas is sizing things to fit when the dimensions are so close to being right, but if you make an image that's half frame size and put it on the timeline you'll get the idea immediately.

If you are taking images from a scanner or camera then the standard procedure would be to resize/crop your images to 654.5?????x480 and then drop them into Vegas, which will then resample them to 720x480. You could also make your images at some multiple of that size (like 720x528, Look! No decimal places!) and Vegas would work with that nicely too (in fact, it's a tiny bit better, but more complicated overall)

If this were a program that expected your images to be 720x480 then the proper procedure would be to start with an image of 720x528 (most applications cite 540 or 534 instead of 528 but it won't matter much when you're done) and then disproportionately resize them to 720x480. This would preserve the right proportions of the original still image.

But Vegas doesn't expect that so I'd stick with some multiple of 720x528 and just let Vegas do it's thing.

Vegas exports stills from an NTSC DV project at 654x480. It opts to keep the image at 480 px high so as not to mess up the interlacing. If you want all the pixels then the way to do it is to put the frame on the clipboard and then paste it into your image editing program.

Rob Mack
TheHappyFriar wrote on 11/10/2007, 5:48 PM
last I recall, you only need to use sizes besides your project size (ie 720x480) if you do NOT want to change the aspect ratio of the still to DV. I make images @ 720x480 & just change the aspect ratio. But, FYI, if you do this you need to accommodate that the images will be "squished" a little when in vegas because if the image program 1.0 aspect to DV's 0.9 something.
rmack350 wrote on 11/10/2007, 6:23 PM
I'm sure we're saying the same things but it doesn't sound like it. In any case, if VegasBaby is just taking stills from a still camera or scanner into an NTSC project, then 654x480 is what the manual probably specifies and 720x528 will also work. The later is technically better but it's not crucial to do it that way.

If Vegasbaby is going to the trouble of changing the stills to account for non-square pixels then he needs to do some other things. Just importing the straight stills at 720x528 would do the job automatically.

Rob
John_Cline wrote on 11/10/2007, 8:49 PM
yes, 720x528 for stills and computer generated graphics.
riredale wrote on 11/10/2007, 11:03 PM
I think implicit in all this is that you are working with an image that is 4x3. One would assume then that for a horizontal dimension of 720 pixels, one should thus have 540 in the vertical dimension.

But the surprising thing (to me, anyway) is that DV is NOT 4:3--it's a bit wider than that. Thus to fit the frame perfectly with square pixels, you would use 528 vertical not 540.

It's kind of moot because the outer 5-8% of the image will be cut off by overscan on conventional TV sets anyway. However, if you view the video on a PC there is no overscan.
Coursedesign wrote on 11/10/2007, 11:11 PM
...and the what, last three versions (?) of Photoshop are able to work with non-square pixels. Each version of PS has gotten increasingly video-savvy lately.

Make your life easier when you can!

rmack350 wrote on 11/11/2007, 2:48 AM
Erm... Yes, photoshop. It's close enough but it'd be helpful if you could set your own pixel aspect ratio. Photoshop's 0.9 is not the same as Vegas' 0.9091.

One thing that's useful with Photoshop is that you can open a new empty file with Photoshop's NTSC DV template and then when you paste images into it photoshop does the PAR correction.

I was just experimenting with it and found that if you drag a layer from a photoshop image that is 648x480x1.0PAR to another photoshop image that's based on the DV template the layer fits perfectly. So while Vegas would say the image should be 654x480, Photoshop would say "You mean 648x480?"

So scale that 648x480 image up to 720 wide and you get an image that's 720x534. Scale Vegas' spec up to 720 wide and you get 720x528. Photoshop's video templates for NTSC are designed around the idea that a 720x486 frame is literally 4:3 (720x540) and so NTSC DV must be 720x534 if you use that logic.

How much does it really matter? You're kind of splitting hairs at this point. If you use Photoshop and use their DV corrected template, the image is 720x480 and it'll fit in the DV frame, but Vegas doesn't make it terribly easy to do it this way since it sees all stills as having a 1.0 PAR. Once you've got a bunch of 720x480 stills imported into Vegas you have to jump through hoops to change the PAR on them.

All this makes it harder than it needs to be. Vegas will do the pixel aspect correction for you and the process is much simpler to just let Vegas do it. And for that you just leave the image's PAR alone and crop the image to any multiple of 654.5x480