Re: 16:9 Help....Square guy in Letterbox Quag

[spencer <spencerhecox(at)sbcglobal.net>]

I should update my math because I wasn't factoring in the the fact that 
NTSC has a 0.9 Pixel ratio. HD has a 1.0 Pixel ratio. This changes the 
math a little for a NTSC Crop.

720/1.777778 = 404.9999(or 405) -- this would work if NTSC was Square 
Pixels like HD


I believe this is a more accurate 16:9 calculation for Square Pixel 
Images that are placed into a NTSC (0.9) world.

720*0.9 = 648
648/1.777778 = 364.5
486 - 364.5 = 121.5
(Or roughly a 61 pixel crop off the top and bottom of your NTSC image.
This would mimic the look that you get when you bring an HD image into 
a NTSC world.)

So for the rest you'd get these numbers:
720*0.9 = 648
648/1.777778 = 364.5
486 - 364.5 = 121.5 (If you round up 61 pixel crop off top and bottom)

720*0.9 = 648
648/1.85 = 350.2703
486 - 350.2703 = 135.7297 (If you round up 68 pixel crop off top and 
bottom)

720*0.9 = 648
648/2.35 = 275.7447
486 - 275.7447 = 210.2553 (If you don't round: 105 pixel crop off top 
and bottom)


_spencer



On Monday, Aug 29, 2005, at 15:31 America/Los_Angeles, spencer wrote:

> Here is how I figure the math.
> Once you build crops you can save them to your factory presets an you 
> won't need to build them again.
> So it's not that big of a pain that DS doesn't do it for you.
> For you NTSC 16:9 you'll want 720x405
> Here is why:
>
> 1920 by 1080 is a 16:9 Image ratio (not pixel ratio... that is 
> different)
> So...
> 1920 / 1080 = 1.777778
>
> For HD 1080
> 1920/1.777778 = 1080
> 1920/1.85 = 1037.838 (or 1038)
> 1920/2.35 = 817.0213 (or 817)
>
> For NTSC
> 720/1.777778 = 404.9999 (or 405)  (486 - 405 = 81 This is why you need 
> a 40 and 41 crop of the top and bottom. You can do this same math to 
> the others to find their crops.)
> 720/1.85 = 389.1892 (or 389)
> 720/2.35 = 306.383 (or 306) (Taking 90 and 91 off your image would 
> look more like a 2.35 crop... which isn't 16:9)
>
> These ratios should work for PAL, DV and HD 720 formats as well.
>
> Also these crops are individual effects. Your Graphics sessions will 
> not respect them. You will have to be sure your titles and graphics 
> remain within the cropped area.
>
> _spencer
>
>
>
>
>
>
> On Friday, Aug 26, 2005, at 15:43 America/Los_Angeles, Ryan Collier 
> wrote:
>
> > SHORT ANSWER: Use the Crop effect and set top to "90" and "91" or
> > vice-versa...
> >
> > LONG ANSWER: Since 16:9 is a ratio, and the image size is 720 x 486, 
> > you
> > have a natural relationship you can use to create a true 16:9 matte.
> >
> > Using simple algebra:
> >
> > 16/9 = 720/x
> >
> > 720*9 = 16x
> >
> > 6480 = 16x
> >
> > 6480/16 = x
> >
> > 405 = x
> >
> > 486 - 405 = 81
> >
> > Split 81 into two equal top and bottom masks... Hence, use the Crop 
> > effect
> > and set top to "90" and "91" or vice-versa...
> >
> > Cheers,
> >
> > Ryan Collier
> > Avid|DS Artist
> >
> > -----Original Message-----
> > From: owner-ds(at)Softimage.COM [mailto:owner-ds(at)Softimage.COM] On 
> > Behalf Of
> > Dsderanged(at)aol.com
> > Sent: Friday, August 26, 2005 6:19 PM
> > To: DS(at)Softimage.COM
> > Subject: OT: 16:9 Help....Square guy in Letterbox Quag
> >
> >
> > Clients......I just love 'em.
> >
> > Cut a :30 spot standard def for air.  Tons of large images pan & scan 
> > and
> > some 35mm film.  Mastered on Digibeta Standard Def 4:3.
> >
> > Client wants to have their spot "Run in a Movie Theatre".  
> > Crazy.....I know.
> >
> >
> > Anyway, the Encoding facility naturally prefers Hi Def Masters, but 
> > will
> > accept a Standard Def 4 : 3 Master with 16 : 9 mask 480i.   Exposing 
> > my
> > ignorance here, but how can I be sure that I am creating a true 16 : 9
> > Letterbox mask in DS.  In Graphics, I typed the letter "I" in a font 
> > that
> > when sized to 525 fills my entire screen top to bottom.  If I tell it 
> > to be
> > 480 size, will this relate to the mask size?
> >
> > BTW, I did try to create a new sequence in 16 : 9 and although the 
> > images
> > looked OK, the standard 35mm film did not.
> >
> > ANY suggestions would be very much appreciated.
> >
> > Thanks....Rick at naked eye
> > a very wet Rick thanks to Hurricane Katrina !
> >
> >
> > ---
> > Subscribe? E-mail Majordomo(at)Softimage.COM with the following text in 
> > body: subscribe ds
> > Unsubscribe? E-Mail Majordomo(at)Softimage.COM with the following text 
> > in body: unsubscribe ds
>
> ---
> Subscribe? E-mail Majordomo(at)Softimage.COM with the following text in 
> body: subscribe ds
> Unsubscribe? E-Mail Majordomo(at)Softimage.COM with the following text in 
> body: unsubscribe ds

---
Subscribe? E-mail Majordomo(at)Softimage.COM with the following text in body: subscribe ds
Unsubscribe? E-Mail Majordomo(at)Softimage.COM with the following text in body: unsubscribe ds