[Richard Benfield]

mike,

Thanks for the reply. Though I haven’t had a chance to try creating an NTSC bitmap in PhotoShop yet, I did find the answer and another solution. I will explain what I have learned below. Don’t feel compelled to read it. I dont presume to think I will be explaining anything new to you or Vince. I am really just posting it for anyone who may search and find this thread. But if you do get bored and what to read it… enjoy… 🙂

Thanks,
Richard

Ok, hopefully someone finds this helpful one day…

The answer was in reading about Pixel Aspect Ratios. I had to read and read and read… and then read a little more. The problem seems to be the complete lack of consistency as to the terminology and the math behind it. Where AR = Aspect Ratio, I have found information on… Sample AR, Image AR, Picture AR, Pixel AR, Frame AR, Display AR, some of them are used incorrectly in different places. Most of them are explained inadequetly (at least everywhere I looked). And the math never worked. Ok, well sometimes it worked, but when it did, it said that the PP preview was incorrect. At 655×480, it just always came out wrong when I tried to calculate it. So let me sum up what I believe I learned and maybe help someone else out that may search and find this thread later. Some of this I had known for a long time, some of it was a new found application of the old knowledge. Anyway, here is my summary of it.

Aspect Ratio is the quotient of somethings width and height.

SAR or Sample AR, Image AR, Picture AR, & Frame AR all appear to be the same, that being the aspect ratio of the picture or videos resolution. So a video with a resolution of 720 x 480 will have an SAR of 1.5.

DAR or Display AR is the aspect ratio that an image is displayed at. If the image is displayed full screen then it is also the aspect ratio of the display device. If the display device uses square pixels then it is also the aspect ratio of the images displayed resolution. So an image displayed at a resolution of 640 x 480 will have an DAR of 1.333 (repeating).

PAR or Pixel AR is much more difficult. I have seen it defined as the aspect ratio of the actual pixel. I have also seen it defined as the quotient of the SAR and the DAR. While I kept on inferring that these were only related to the playback pixels, they are also applicable to the capture pixels. So the capture device or resultant image also has a PAR. And if the capture/image PAR and the playback/display PAR dont match, the image will not look right.

I finally stumbled upon a web page directly from Adobe that explained some additional and VERY important things. Here is the link for any who may want to see it: https://help.adobe.com/en_US/PremierePro/4.0/WS03BF7479-8C7B-4522-8C75-210AD102524Ea.html

Among the things it explains is that DV NTSC is .91 (which is closer to accurate, but still not quite right) and that PP will show the PAR it believes an file is based on. When I create a sequence it asks what preset to use. When I look at the DV NTSC preset, it shows the PAR is actually .9091. When I import a Type 2 DV video, it shows that its PAR is .9091. When I import a bitmap, it shows that its PAR is .9091… (Did you catch that?) As indicated by mike, bitmaps created in normal image editors are square (well the pixels are). The PAR is actually 1 not .9091. Thankfully, that same web page explains that you can manually correct the PAR by using the Interpret Footage dialog box. Immediately upon chaging the bitmaps PAR it was re-rendered in the program monitor correctly.

Well that is all fine and well, but what about this 655 x 480 business in the program monitor? It just didnt make sense… until I calculated the PAR for a 720 x 480 SAR and a 655 x 480 DAR. The result? A PAR of .909722… Finally, it makes sense. A little more math showed me that 655 x 480 using square pixels is as close as you can possibly get to a PAR of .9091… So there it is… mystery solved. So in fact, it would appear that PP program monitor is the only player on my computer that will accurately display a 720 x 480 video with a PAR of .9091 such as Type 2 DV… the other players I kept using as a reference were displaying it with an incorrect PAR of 1. The only thing that PP did wrong. was assume that my bitmap had a PAR of .9091 instead of 1. But since it has an easy method to manually change the clips PAR. its point Adobe…

Thanks,
Richard Benfield

[Richard Benfield]

Hi Vince,

Thanks for the response. The problem was in fact related to the pixel aspect ratio. I will post my little ‘book’ explaining my findings, in a response to mike at the end of the thread. Just in case your bored and want to read it… 🙂

Regards,
Richard

[Richard Benfield]

arc,

Thanks for the reply but I was using High Quality. However, it still showed 655 x 480 playback resolution. I will explain why at the end of this thread.

Thanks,
Richard

[Richard Benfield]

Hi Mike,

Thanks for the response. My displays are fine. I have two Dell 1908FPs with a native resolution of 1280×1024. They are both driven by a NVIDIA Quadro FX 1700 and are running in their native resolution. Also the problem is noticable on the same display when looking at the source vs. the preview vs. the render.

Thanks for that suggestion, it was actually a very interesting test with some unexpected results. Before I write my little book explaining what I did, I would ask (if you have an opportunity) for you to export your title to a Bitmap and measure it again. I wanted to upload my results, but they are too large and I can’t access my website right now. I will try to access it later and upload the images and link them from this thread. As an aside, the way I was using it, I had my Preview Panel undocked and on my second display, set to 100% and sized larger than the preview. However, for the sake of consistency with your suggestion, I did not use it that way for the tests below. Instead I did everything on the primary monitor as you described. That said, here is what I did and what I found.

I created a new project using the DV – NTSC, Standard 48kHz preset.
I created a new Default Still, Title.
Within the Safe Margin, I created a perfectly round white circle (shift drag) and centered it.
Within the white circle, I created a perfectly square black rectangle (shift drag) and centered it.
I added the title to the sequence and expanded it to 15 seconds.
I selected the preview panel and pressed the tilde key.
I measured it and then I took a screenshot and cropped it to only the black back ground portion (the actual preview).
I pressed tilde again to revert to the normal view and selected File, Export, Media.
I selected Windows Bitmap for the Format and NTSC Bitmap for the preset and saved it.
Results at the bottom

Then using an image editor, I created new blank image with a 720×480 canvas.
I created a perfectly round black circle against a white background.
I created a perfectly square white rectangle in the black circle.
I saved it as a 24 bit Windows bitmap for use in a sequence.
I created a new project using the DV – NTSC, Standard 48kHz preset.
I selected File, Import and opened the test pattern bitmap.
I added the imported bitmap to the sequence and expanded it to 15 seconds.
I selected the preview panel and pressed the tilde key.
I measured it and then I took a screenshot and cropped it to only the black back ground portion (the actual preview).
I pressed tilde again to revert to the normal view and selected File, Export, Media.
I selected Windows Bitmap for the Format and NTSC Bitmap for the preset and saved it.
Results at the bottom

Measurements were confirmed by checking the canvas size and number of pixels high and wide in the resultant bitmaps.

Adobe Title Results

Previewed Measurements
Circle – Width and Height were Equal 378×378 pixels
Square – Width and Height were Equal 275×275 pixels
Canvas – Width and Height were 655×480 pixels
(Note: The circle and square were the correct aspect ratio, but the canvas was NOT)

Rendered Measurements
Circle – Width and Height were NOT Equal 415×378 pixels
Square – Width and Height were NOT Equal 303×275 pixels
Canvas – Width and Height were Correct 720×480 pixels
(Note: The circle and square were NOT the correct aspect ratio, but the canvas WAS)

Imported Test Pattern Results

Source Measurements
Circle – Width and Height were Equal 477×477 pixels
Square – Width and Height were Equal 330×330 pixels
Canvas – Width and Height were 720×480 pixels
(Note: The circle, square, and canvas were ALL the correct aspect ratio)

Previewed Measurements
Circle – Width and Height were NOT Equal 434×477 pixels
Square – Width and Height were NOT Equal 301×330 pixels
Canvas – Width and Height were 655×480 pixels
(Note: The circle, square, and canvas were ALL the WRONG aspect ratio)

Rendered Measurements
Circle – Width and Height were Equal 477×477 pixels
Square – Width and Height were Equal 330×330 pixels
Canvas – Width and Height were 720×480 pixels
(Note: The circle, square, and canvas were ALL the correct aspect ratio)

Can anyone else confirm this behavior? If this is correct, then it means that not only are things not rendered in the preview accurately (not that big of a problem), it also means that Titles and possibly other content added by Premiere Pro, is not rendered correctly in the exported media (more of a problem).

Thanks in advance again,
Richard