Two questions really...

What makes images captured with CCDs so different from images on chemical film? I mean apart from the obvious, like low saturation and lower resolution. There's something about the way light is registered on film and CCD that is very different but what is it? Chemical photos always seem "warmer" than CCD photos. I read somewhere that film is much more tolerant of overexposure which may be part of the answer. Or maybe the difference lies in the gamma?

Second question: does anyone have a recipe to make a CCD scan look more like a chemical photograph by playing around with settings in Photoshop?

Thanks!

-- Michel Lefebvre (glaive@total.net), November 04, 1998

Answers

Don't know about the "warmer" part - that's maybe just color balance. Can't really explain some of the other stuff here, without graphs, etc, but a big difference is to be found in the "D log E" curves of film - the relationship between density and exposure. Film nicely trails off at the high and low end, basically going to a much lower contrast as the light level gets to the extremes (either low or high) that the film can respond to. CCDs are basically linear devices, with a "gamma" curve applied in the electronics. This means that both highlights and shadows tend to "clip," or stop responding abruptly, rather than trailing off gracefully the way film does.

Suggestions on the artistic stuff I'll leave to people with talent...

-- Dave Etchells (web@imaging-resource.com), November 11, 1998.