On 8/18/2010 11:32 AM, John Hudson wrote:
> I have been requested to supply a few digital images for showing on a big
> screen tv [let's say one of those 50" or 60" plasma tv's] using a laptop as
> the projection / control / image sequencing device. There may be upwards of
> 30 feet between the audience and the tv screen.
>
> An 800 x 600 pixel image at a 100 ppi resolution makes for a good web based
> image.
>
> An 1800 x 1200 pixel image at 300ppi resolution makes a nice 6" x 4" print.
>
> Can someone please advise me what pixel size and what ppi resolution is
> required for a sharp big screen tv image viewed at upwards of a 30 foot
> distance,
First of all, ppi resolution is irrelevant to video images. You can prove it to
yourself. Make one 800x600 at 300 ppi
and another at 30 ppi. Both will be identical on your monitor.
That's because the pixels are simply shown 1 to 1 on the screen. If you want to
make an image or images a specific size
in inches or mms on screen, you need to know the pixel pitch of the screen and
to do that math. However, on another
screen of different size or different pixel resolution, it will be a different
physical size.
It's the same for a TV. You find out the actual pixel resolution of the
combination of computer output and TV and size
your images to fit. They will then exactly fill the screen. It doesn't matter
what physical size the screen is or how
far away the audience is. The image is constrained by the TV and the device
driving it.
A full HD TV (1080) is 1920x1280 pixels, partial HD is 1280x720 (720). (The
little letter after the vertical rez number
means: i = interlaced, p = progressive. You needn't worry about that here.) So
the maximum image size you might need is
1920x1280.
However, you may also be limited by the video capabilities of the computer
driving the TV. You should find out from the
owner what the output pixel resolution of the computer is, and match your
images to that.
Anything other than matching image size to native resolution of the video
output/tv combination will result in either an
image too big or small or adjustment to fit it to screen that will usually
result in poorer image quality. For example,
most HDTVs have a display mode that stretches 720 images to 1080, to fill the
screen with images from DVDs. Some DVD
players have a similar function. But the on-screen result is not as good as an
image properly sized to begin with.
Projection Moose
> jh
>
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