Pitfalls of digital projection?

[mike_smith2]

I am investigating the problems in trying to run a digital

photographic competition as an alternative to the normal 35mm slide

variety

 

One issue that has been pointed out to me is the problems between

landscape and format format pictures. Landscape can project 640 x

480 (or higher in SVGA mode), but the portrait equivelent is

restricted to 3xx x 480 and would not be 480 x 640. I assume that

any picture sized 480 x 640 would be compressed and therefore

potentially suffer from induced projection compression artefacts. So

there is potentially a quality issue penalising portrait pictures

immediately against landscape.

 

Has anyone run a digital photographic competition and what pitfalls

did you find.

[marshall]

Well, there are actually far more pitfalls in digital projection for competition than just the projector. But starting there, I think I'd be uncomfortable running the competition with a projector limited to 640x480. When we have projected a club I participate in, we had a higher resolution projector (wish we could buy one), and limited all entries to 600 (or maybe 800) on the long side, enabling us to project them all at essentially the same size. I'd rather see even larger projection for detail, but it worked ok.

 

Compression doesn't really have to be an issue. If you took images at 800 long and compressed them lightly, they'd be fairly large in transmission, but not slow in projection, and they'd look reasonably good. Ok, the detail would still be less than a projected slide or a higher-res digital file, but the compression shouldn't be that big an issue.

 

Good luck.

[jimstrutz]

Get a newer projector that has native XVGA (1024x768) resolution or higher. Make sure XVGA is it's native resolution, not interpolated XVGA. Then set a limit of 768 for the longest dimension of any image, and tell all contestants to resize and submit images to that limit. Then every shot is treated equally and nothing is compressed.

[eosbob]

My club (Pontiac Photographic Society, Waterford, Michigan, USA) has a Digital Projection category as well. I don't recall the exact dimension but we have a set limit for the longest edge be it vertical or horizontal. We also specify 90dpi to keep the files uniform and manageable. It has been very popular, allows those who no longer (or never did) shoot slides to compete beyond the print category.

[benj_c]

<i> robert: We also specify 90dpi to keep the files uniform and manageable. </i>

<br>

What do you mean by 90 dots <u>per inch</u> ? Sorry to poke, but this common misuse of terms is one of my pet peeves, which I'm compelled to fight :).

<p>

There is, in fact, no "distance" inside the submitted computer file. The file contains ONLY dots.

<p>

"DPI" makes sense only when laying those dots down into the real world (eg on a printer or display), or picking them up from the real world (eg scanning or digital camera.)

<br>

For example, if a given file is 768 pixels in height, then displaying it...

<br>+ on a 17 inch monitor = 768dots/10.2inch = 75dpi

<br>+ on a 21 inch monitor = 768dots/12.6inch = 60dpi

<br>+ on a 32 inch projection = 768dots/19.2inch = 40dpi

<br>+ on a 64 inch projection = 768dots/38.4inch = 20dpi (the same projector moved away from the wall)

<p>

(Apologies if I misunderstood the context due my sensitivity to the issue.)