[A summary of this article was first published
in the September, 2004, edition of "Larry's
FCP Newsletter.”]
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.
GOAL 1
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.
Format |
Create image
at |
Resize image to |
| DV-NTSC 4:3 |
720x531 |
720x480 |
| DV-NTSC 16:9 Anamorphic |
868x480 |
720x480 |
| 601-NTSC 4:3 |
720x538 |
720x486 |
| 601-NTSC 16:9 Anamorphic |
868x486 |
720x486 |
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…
GOAL 2
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:
Format
|
Create image at
|
Resize image to
|
| DV-NTSC 4:3 |
720x540
|
720x480
|
| DV-NTSC 16:9 Anamorphic |
853x480
|
720x480
|
| 601-NTSC 4:3 |
720x547
|
720x486
|
| 601-NTSC 16:9 Anamorphic |
853x486
|
720x486
|
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
http://store.yahoo.com/dvdinternational/dve.html
or
http://www.ovationsw.com/avia.html
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.
This article was first exercepted in the
September, 2004, issue of "Larry's
FCP Newsletter," a very cool FREE monthly Final Cut Pro
newsletter -- subscribe at Larry's web site: www.larryjordan.biz.
Text copyright 2004 by Carl Jacobs. All rights reserved.
