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Re: [OM] ( OM ) Not really OM - but digital -> 35mmm slides

Subject: Re: [OM] ( OM ) Not really OM - but digital -> 35mmm slides
From: "John A. Lind" <jlind@xxxxxxxxxxxx>
Date: Mon, 02 Sep 2002 20:41:28 -0500
At 18:43 9/2/02, Brian Swale wrote:
Hi folk,

I have a friend of many years' standing with whom I used to share a flat in
New Zealand in the 1970s, and who works for the USDAFS in the WV / MD
area. He spends a lot of time talking to classes and projecting slides. Now
he's thinking of digital. My first question was "Why?".

[snip]

Responses appreciated.

Brian,
My question is also "Why?"
I presume he is projecting to at least a 60 inch screen, if not something approaching an 80 inch. Very large screens are commonly found in schools and other commercial settings. Now imagine using a typical digital photograph and exploding it to that size. This is ***not*** the same as line art which fares reasonably well in digital projection.

The beauty of the slow and medium speed 35mm slide films are their extreme fine grain. Even if projection size exceeds resolving power of the film, as it can easily do, it degrades gracefully without falling apart. Not so with digitals. In the attempts I've seen projecting digital photographs to a large screen at work using something close to reasonable file sizes, the images fall apart completely with outright ugly pixelation. Do the math to find the size of an individual pixel in a digital image of *reasonable* file size when it's projected to a 72 inch screen. For a 1024x768 file they're about 1/16th inch square. Now compound this with common, lossy compression techniques used to make reasonable file sizes of them (which likely has greatest uglification effect).

I recommend considering conversion digital for this purpose very carefully and would want to ***see*** projections of photographs ***before*** buying a camera or digital projector, and be ***certain*** of the exact process used to replicate anything that looks OK. This has been an utter failure where I work using common digital cameras in the 3MP range and common digital projectors for "Powerpoint" presentations. It was a BIG surprise to those who tried it ("Gee, it looked just fine on the [17 inch] computer screen.") but it was no surprise to me.

Perhaps someone else on the list has been able to project digital photographs of *reasonable* file size to large screens using digital projectors. If so, I'd certainly like to know how it was done (and the file sizes). Nobody where I work has been able to do it yet, and we have no shortage of techno-geeks.

-- John


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