6 Replies Latest reply on Jan 16, 2010 10:32 AM by able123

    confirmation....still image dimensions from 16:9 720x480

    Level 4



      I just exported a frame from a 720x480 16:9 DV NTSC video clip.  I tried doing it from Premiere and it would only give me a bmp choice.  I then did it from Streamclip, which gave me TIF, JPG and BMP choices but it did not really matter, because TIF is only 8 bit, just like the BMP in premiere...


      The dimensions of the still image ( frame ) are (according to ps) 853 x 480 .


      Is that correct for all frames exported from 720x480 16:9 DV NTSC videos ?


      Reason I ask, is I want to create images that match ( size wise ) so I can make a slide show on a DVD eventually...






      ps  funny, I thought the 720 dimension would be favored and the height would be "squeezed" to something smaller than 480...for the 16:9 ratio.

        • 1. Re: confirmation....still image dimensions from 16:9 720x480
          Harm Millaard Level 7

          Actually a widescreen NTSC sequence has 720 x 480 resolution with a PAR (pixel aspect ratio) of 1.2121. What you are seeing is the same dimensions but with square pixels, because BMP's only use square pixels.

          • 2. Re: confirmation....still image dimensions from 16:9 720x480
            Level 4



            Ah Ha !  Geez...I KNOW that the pixels are not square in NTSC, and ARE square in bitmaps, but I didn't even THINK about that last night when I was dealing with this...How can I be so dumb sometimes ??  Geez....


            Thanks Harm.


            If you could elaborate a little....I'm not very swift with math and ratios.



            I just got out the calculator....and looked at GSpot...with a 720x480 widescreen AVI opened...


            It is saying, par 1.185 (32:27)...for this particular AVI file that I made exported from Premiere last night...

            Now, if I multiply 720 x 1.185 I get 853 !!!   How cool is THAT....so I guess that's how I come up with the dimension of a bitmap when I do this in future...


            And when I multiply 720 x .2121 (rather than 1.2121) I get 152.7...close enough !....same as 853...


            How come there's two different ways of doing that ??


            But my numbers are weird for 1.1212.....  what am I doing wrong ??


            Should there be one way to go about doing this math stuff ???


            Anyhow, you've already answered my question and thanks a lot....   square pixels !  ..didn't even think of that...



            • 3. Re: confirmation....still image dimensions from 16:9 720x480
              the_wine_snob Level 9



              Remember that the PAR is 1.2121 and not 1:2121. Note decimal vs colon.


              In 4:3, the pixels are 0.9 (roughly), so they are taller, than wide. With 1.2121, the pixels are wider, than tall. Obviously, when square (1.0), they match vertically and horizontally.


              Good luck,



              • 4. Re: confirmation....still image dimensions from 16:9 720x480
                Level 4



                But how do I do the math ??  I mean...If I multiply 720 x 1.185  I get 853...but not with 1.2121....what am I doing wrong ??



                • 5. Re: confirmation....still image dimensions from 16:9 720x480
                  Harm Millaard Level 7



                  You are not doing anything wrong. It is that with the advent of CS4 PAR's were changed and presumably Adobe changed the PAR to reflect 704 x 480 NTSC resolution, instead of 720 x 480. Otherwise the calculator would have shown 873 horizontal resolution. This is where things get rather confusing and I don't have the definite answe. Maybe someone else (Dennis?) can tune in here.

                  • 6. Re: confirmation....still image dimensions from 16:9 720x480
                    Level 4



                    Aha....yes, I am getting the 873 number ..   hehe..then I tried like subtracting 720 from 873, and all sorts of stuff to see if I could make sense of it...but to no avail.


                    Thanks a lot for your help...


                    Maybe for the sake of making it easier to figure out the dimensions of the still frame bitmap the par was changed on the exported widescreen from 720x480 space.... to eliminate more calculations to accomodate the square vs rectangular pixels.... anywho...thanks.


                    On a side note


                    Using Premiere cs3


                    ....  I did so many different things last night - conversions, exports, etc.  .... I'm getting a little hazy about exact "routines" I did...but I think I tried like 3 times to export a frame from Premiere of the widescreen AVI and they came out squashed (720x480).  I did it from Quicktime and they came out OK...not squashed ....853 x 480 ....which I was doing to make images to go back into the project.


                    When I used photoshop to (with keep proportions unchecked) change image size of Premiere frames exported (720x480 to 853x480) they look great...


                    But I was wondering why Premiere doesn't do the export frame at 853 x 480 directly....weird...