[ A summary of this article was first published in the September, 2004, issue of
Larry’s Monthly Final Cut Studio Newsletter. Click here to subscribe. ]
What is the correct size image to start with to make Photoshop documents look right when imported into FCP? There are so many different numbers floating around the forums and various versions of FCP manuals. What gives, dude?
As proof that life with FCP is a swirling circus of choices–and thanks to a SMPTE document recently unearthed–there are actually two sets of numbers that are arguably equally correct depending on which of two mutually-exclusive goals you choose: either 1) have the images be correct on your NTSC display or 2) have the images be correct as viewed in FCP on a computer display. Pick one. You can’t have both.
You want square-pixel images created in Adobe Photoshop or After Effects to appear geometrically accurate (a circle is a circle) when edited in FCP and viewed on rectangular-pixel NTSC displays.
To achieve this, you have to: make the image match the officially recommended SMPTE pixel aspect ratio for NTSC 4:3 interlaced images: 0.904
Method A. In Photoshop CS (and After Effects 6) simply choose the appropriate NTSC DV or NTSC D1 preset when creating a new image (or Composition in AE). Done. Easy. The new image will have both have the correct SMPTE-recommended pixel aspect ratio to make it look right on your NTSC display and Photoshop will adjust the image to appear correctly as you create it. No more creating at one size and resizing it for import into FCP.
Bonus! You don’t have to track multiple documents through the workflow; one in the original size for future revisions back in Photoshop and another in the corrected size ready-to-import-into-FCP.
The DOWNSIDE to Method A. In order to display the image correctly on your computer monitor, Photoshop has to resize on-the-fly, which can make the image appear low-rez. (In After Effects, you have to turn “Pixel Aspect Ratio Correction” on in “View Options…” to display the composition presets properly. AE will warn you that while this view is not at maximum image quality, it will not affect output.) If this low-rez view bothers you, you may have to use Method B.
Method B. Photoshop versions 7 and earlier, and After Effects before version 5, I think, lack those handy presets, so you have to do the established practice of “Create at one size. Resize to another for FCP import” and use these numbers to do it.
FormatCreate image atResize image to DV-NTSC 4:3 720×531 720×480 DV-NTSC 16:9 Anamorphic 868×480 720×480 601-NTSC 4:3 720×538 720×486 601-NTSC 16:9 Anamorphic 868×486 720×486
You probably haven’t seen these particular numbers show up anywhere before, but they’re based on previously established, yet apparently little-known, information: the actual SMPTE Recommended Practice for pixel aspect ratios (SMPTE RP 187-1995).
The DOWNSIDE to both Method A & B. Images created using the two above methods will be geometrically incorrect when viewed in FCP on your computer display, particularly if it’s an LCD display being driven with its digital input (DVI or ADC). The error isn’t much–less than 2%–but a circle created using either of the above methods will not be a circle when viewed in FCP. It also will not match the shape of images created in FCP. Which brings us to…
You want square-pixel images created in Photoshop, or After Effects, to appear geometrically accurate (a circle is a circle) when edited and viewed in FCP on your computer screen OR you want circles created in Photoshop and imported into FCP to exactly match circles created in FCP.
To achieve this, you have to:
Make the square-pixel Photoshop images match FCP’s non-SMPTE-recommended pixel aspect ratio of .888888888889 (because FCP HD calculates the aspect ratio as 8/9).
To do this, you have to use the latest numbers as laid out by Apple for FCP and “Create at one size. Resize to another for FCP import”
These numbers and details for the procedure can be found at http://docs.info.apple.com/article.html?artnum=36836
In comparison to the SMPTE numbers, here are the Apple recommended numbers:
FormatCreate image atResize image to DV-NTSC 4:3 720×540 720×480 DV-NTSC 16:9 Anamorphic 853×480 720×480 601-NTSC 4:3 720×547 720×486 601-NTSC 16:9 Anamorphic 853×486 720×486
The DOWNSIDE to using these numbers:
While geometrically correct when viewing the image in FCP on a computer monitor, they do not match the SMPTE recommended pixel aspect ratio, so they will be slightly distorted when viewed on an NTSC monitor.
But, wait! There’s more…
How do I know if my NTSC monitor’s geometry is set to SMPTE’s recommended .904 pixel aspect ratio?
Well, you don’t but it probably isn’t. But with a little effort and the right tools you can get it close. You’d have to feed the display the proper test pattern and adjust the displays geometry using a ruler and special service menus built into most professional, and many consumer, displays. Even then, you may never get it to be perfect and all CRTs will drift over time.
That’s why deciding which numbers to use, Apple’s or SMPTE’s, is at some level arbitrary. Especially when you consider that moving just a couple of inches off-axis from your NTSC monitor will introduce more distortion into the image than the difference between the SMPTE and Apple pixel aspect ratios.
So use whichever numbers and methods are easiest and quickest for you, and go spend the extra time you saved not wringing your hands over this with friends and family.
– – –
By the way, for those of you outside North America scratching their heads about this, SMPTE (the Society of Motion Picture and Television Engineers) is the official committee that determines the engineering specifications of NTSC video. There are similar governmental bodies that set the standards for PAL video. And, like NTSC, PAL video uses a non-square pixel. However, a PAL pixel is a different size than the NTSC pixel (which should, of course, surprise no one).
Apple’s web site provides the necessary conversion numbers for PAL video. You may talk amongst yourselves to decide if Apple’s numbers are correct.
Thanks to Charles Poynton, author of “Digital Video and HDTV Algorithms and Interfaces” and Bruce Jacobs, Twin Cities Public Television’s Chief Technologist for unearthing these standards and the numbers to go with them.
Text copyright 2004 by Carl Jacobs. All rights reserved.
One Response to Getting PhotoShop Images to Look Good in Final Cut by Carl Jacobs
I was confused for a long time regarding why I would sometimes see a pixel aspect ratio of 10:11 (approximately .909) and at other times 8:9 (approximately 0.889) associated with 601-NTSC 4:3 video (720×480 or 720×486.) I consulted two books by Charles Poynton (Digital Video and HDTV Algorithms and Interfaces, and A Technical Introduction to Digital Video), as well as the videohelp.com forum, in order to help myself figure this out.
I think that I understand it now. The “Rec. 601” standard entails cropping “blanking transition samples” off the left and right sides upon display. (These “blanking transition samples” are not to be confused with “blanking intervals” that are not part of the 720×480 or 720×486 raster.) While I am not familiar with professional studio equipment for displaying such video, I suspect this usually happens automatically. But for working with this format on a personal computer, note that 720 x .909 leaves you with approximately 654, not 640 (despite 640×480 being 4:3.) I found it helpful to understand “Rec. 601” entails “production aperture” (the full 720×480 raster, or approximately 654×480 when scaled according to the .909 pixel aspect ratio), and “clean aperture” (the remaining portion of the raster after cropping pixels off the left and right sides.)
On the other hand, some 4:3 video may be mastered using a full 720×480 raster, in which case, the pixel aspect ratio is 0.889. (Note that 720 x 0.889 does equal 640.) I think such video would not be according to “Rec. 601”, however.
References:
“The term pixel aspect ratio was first coined when ITU-R BT.601 (commonly known as “Rec. 601″) specified that standard-definition television pictures are made of lines which contain exactly 720 non-square pixels. ITU-R BT.601 did not define the exact pixel aspect ratio but did provide enough information to calculate the exact pixel aspect ratio based on industry practices . . .”
http://en.wikipedia.org/wiki/Pixel_aspect_ratio
“. . . a total digital line length of 720 pixels was chosen. Hence the picture will have thin black bars down each side. . . 704 is the nearest mod(16) value to the actual analogue line lengths, and avoids having black bars down each side.”
http://en.wikipedia.org/wiki/Overscan