#Aspect Ratio
5 messages in this thread
Steve,
Is there a formula for calculating correct aspect ratios for non-standard
frame dimensions?
Michael S. Flynn
>>>>Is there a formula for calculating correct aspect ratios for non-standard
frame dimensions?
Michael, The rule number one is not to get confused… <BG> Aspect ratios
exist only for different display systems — for printing it is always 100%
(1.00) It is a question of how much you have to expand or condense the hight of
your rendering box (x pixels by y pixels) to fit of display area ractangle.
There are many ways to calculate the proportions… I am sure it will stay
better in your mind if you pick your own method…
Pawel
Pawel,
When you talk about different display systems, do mean different monitors
or or different media like TV or Video? The default aspect ratio of 320 x 200
is 0.8333, 640 x 480 is 1.000 and .TGA (512 x 486) is 1.266. If someone asked
for a 500 x 400 image, this is not proportional to standard VGA and .TGA files.
I'm just wondering how the aspect ratios of the standards were calculated and
if that method can be used for any frame dimension.
Michael S. Flynn
Michael,
I have no idea how the standards were established other than the standards are
what they are — that is the VGA width/hight ratio = 1.00. The display systems
include all the things you mentioned — TV "pixels" for example are not square,
so you have to build-in the distortion in order to display the image with
correct proportions… You could, for example, play with your monitor's
horizontal and vertical controls to achieve similar distortions and calculate
the new aspect ratio by measuring the new width + height and comparing it to
VGA rectangle… (this could be one of the tricks for simulating a BIG SCREEN
animation <BG>).
Here is an example for your 500 x 400 image, (remember 640 x 480 is standard):
640 w 640 x h
— = — or ——-
480 h 480 x w
which is:
640 x 400
——— or 256,000 : 240,000 = 1.0666(6)
480 x 500
So our aspect ratio is 1.067, which means that your new frame is 106.7% higher
than the standard VGA if you scaled the frame proportionally to fit the VGA
width…
>>>and if that method can be used for any frame dimension.
Of course, as long as you understand that those things are not arbitrary or
whimsical but given constrains of output devices.
Pawel
Pawel,
Thanks for the breakdown. The thing that I find annoying is that
non-standard frame dimensions are not proportional; I am a math-oriented and
symetrical-type person – sometimes I have to force myself into asymetry to keep
from being borng.
Michael S. Flynn