16x9 guidelines

[Corey Doyle]

I have something shot with 16x9 guidelines and now I want to crop. I need to know the best way to go about doing this. I am using Premiere 6.5. Using the "clip" filter, I have been just setting the top and bottom to about 14, but I would like a better way to do this if possible. Also a more accurate placement of the bars. Any suggestions?

Thanks
Corey

[Rob Lohman]

Actually your black bars must be 58 pixels high (NTSC) or 72 pixels
(PAL), not 14 for a correct fake 16:9 letterbox image. This sizes
take the pixel aspect ratio into consideration (which most people
do not, but should) and have been verified with someone in the
business.

As to how you can best manage this is either by using the Premiere's
Clip function (under Transform) or make a MASK in a Paint
program like Paintshop Pro or Photoshop. Keep in mind that
the clip function uses percentages instead of pixels. So if you
need to crop 58 pixels of an NTSC image you need to set the
slider for top & bottom to 12%.

[Ken Tanaka]

Welcome Corey,
If you need an accurate 16:9 mask I have one posted at my .Mac file sharing page in Photoshop format. Please help yourself.

[Corey Doyle]

Hey thanks alot for the info.

I think i'm going to use your photoshop mask.

Thanks again
Corey

[Ken Tanaka]

Corey,
You should note two points.

1. Rob recently detected some aliasing artifacts in my original mask. I've corrected those and uploaded a new mask to my .Mac homepage.

2. My mask was generated directly from a Final Cut Pro 16:9 built-in mask and uses 49 pixels for the height of the black bars. Rob has performed calculations indicating that the "true" height of these bars should be 58 pixels. So you may want/need to alter my mask slightly depending on how much precision you need.

[Robert Knecht Schmidt]

I hope I'm not veering this thread into a right angle, but if I have footage shot in a 16 × 9 aspect ratio (1920 × 1080 pixels) and I want a scope aspect ratio, does anyone know off the top of their heads how many rows of pixels need to be chopped? Thanks--

[Rob Lohman]

That is a tricky one, Robert. I assume with scope you mean a
2.35 image?

For a non-anamorphic NTSC picture that you want to add letterbox
to the picture should be 276 pixels high (each bar being thus
(480 - 276) / 2 = 102 pixels high).

However since it is already anamorphic one would need to adjust
the pixel aspect in the formule and you would get a 368 pixel
picture which yields 56 pixel high black bars.

Since you claim a higher resolution I've redone the calculation
at both 0.9 (normal NTSC) and 1.2 (widescreen NTSC), this yields:

734 picture, 173 pixel high black bars
-or-
980 picture, 50 pixel high black bars

Try these numbers out? I suspect the smaller ones to be the
correct ones (since this use the anamorphic pixel aspects). Do
let me/us know how this experiment goes. I've never used my
math on an anamorphic signal before so I'm doing a bit of guessing
here!

[Robert Knecht Schmidt]

The footage isn't NTSC at all, it's HD (16 × 9 aspect ratio, 1920 × 1080 square pixels)...

[Rob Lohman]

If I input 1920x1080 with square pixels and a 2.35 mask I get
the following figures out:

Picture height: 816 pixels
Height of each black bar: 132 pixels

That should yield a 2.35 anamorphic picture Robert!

Let me know if this "looks okay", otherwise should me an e-mail