contrast in p&s digital cameras vs film

External Since: Oct 04, 2005 Posts: 833

Doug McDonald wrote:

> Most B&W negative film is quite linear in the toe, and only
> in the toe. Remember that it has fog. To see the linearity you
> have to measure the transmission in the toe region, correct for
> the possibility of overlapping grains if the transmission drops much below
> 85% (after compensation for surface reflection) and then
> subtract off the background. Just before CCDs obsoleted film,
> astrophotographers took multiple short exposures where the
> transmission of the negative in regions of maximum broad field
> density (i.e. excluding stars) was about 20 to 50%, scanned
> them and added them together. This produced lower limiting
> broad field density than using one long exposure, simply
> because one no longer lost information to overlapping grains.
> But it was very very ticklish business.
>
> Doug McDonald

Doug,
I know of only one person who stacked scanned film astrophotos.
Did a great job, by the way, and the response need not
be linear for it to work, especially the same subject exposed
the same amount of time. People do that now with jpegs.
But scanned film brought out more faint detail than one could
print anyway, so it was/is a win/win situation.

Roger

External Since: Jun 02, 2007 Posts: 109

On Oct 14, 9:07 am, acl <achilleaslazari....TakeThisOut@yahoo.co.uk> wrote:
> On Oct 14, 9:05 am, "Roger N. Clark (change username to rnclark)"
>
>
>
> <usern....TakeThisOut@qwest.net> wrote:
> > H.S. wrote:
> > > Hello,
>
> > > I was wondering if anybody can comment on the quality of contrast in the
> > > pictures taken with a point and shoot digital camera compared to the one
> > > obtained on 35mm film.
>
> > > I have seen pictures from Canon A520 and a few older models. I can
> > > usually pick them out from the ones scanned from negatives quite easily.
> > > The ones taken with digital cameras usually appear to have less contrast
> > > and less amount of colors (less saturated colors?).
>
> > > Anybody know of any recent digital cameras in which the colors are
> > > better and we can have more contrast? I know this may appear to be a bit
> > > vague, but related comments are welcome.
>
> > The main reason is that film has a toe in its characteristic
> > curve and digital cameras are linear.
>
> Is that so? My reading of the Gurney-Mott business (a couple of years
> ago and very superficial) led me to conclude that the formation of the
> latent image on film is also a linear process (as long as you're not
> in the region of low or high intensity reciprocity failure). The
> characteristic curve comes when you develop it. So I don't see how
> this is any different from digital capture, where the detection is
> linear and you then apply a curve. I'm not an expert and just scanned
> the paper quickly, so may have completely misunderstood it.
>
> I'd say the difference the OP see is because of the processing, which
> I think deserves a lot more attention than people seem to think. I
> know this is also what you say below, but I think saying that one is
> linear and the other isn't is not accurate (as it refers to different
> stages of capture/development in each case). But maybe I am wrong.
>
> > They are also linear
> > at the low end after the "gamma" tone curve is applied.
> > Learn to use curves to add an s-curve response to give a
> > film-like response. You can boost contrast in camera, but
> > post processing gives more control over shadow and highlight detail.

Depends on the film. Some are quite linear, others are quite S-
curved. Look at the characteristic curves of various films.