Film versus DSLR dynamic range

Started Jul 24, 2007 | Discussions thread
The Davinator
The Davinator Forum Pro • Posts: 22,077
Re: Film versus DSLR dynamic range

Julia Borg wrote:

Anyway, you don't want to use a
media with huge DR, because you will get a very flat image as a
result with no contrast whatsoever.

presuming one does not know postprocessing and how to compress DR
there into something useful.

The advantage film still has over digital is elsewhere. Linear range
is similar, but film wins outside of that range. It's due to the
way digital and analogic react to saturation.

it is more a matter of raw conversion vs. film development. in both
cases latent images are pretty linear.

Film is MOST CERTAINLY NOT linear. I suggest you check out the response curves of various B&W films....nothing could appear less linear. If you have ever processed your own B&W film, you'd already know this!

When you saturate a digital device, it clips. In 8 bits, anything
above 255 is 255. That's the dreaded white hole in your blown
highlights.

when you saturate film it clips too - right to the base or to max
density.

Very, Very hard to clip certain films. I can routinely overexpose Tri-X and NPS160 by 4 to 6 stops and easily retain highlights. Let's see you drag 6 stops of overexposure in a digital file back into a useable image.

btw 255 is not used any more in processing of digital captures.

Worse, not all channels clip at the same time - causing
color shift when the highest channel clips while the other keep
responding.

same as with film if color temperature is un-balanced.

Another problem with digital is that CCD/CMOS are absolutely linear :

again, latent image is very close to linear on the film too.

No, it's not.

twice the amount of light will cause the output of the sensor to
double.

twice the amount of light will cause twice the number of silver
halogen grains to restore to silver forming latent image. H&D curve
is a curve for developed film, not for exposed film.

On the other hand, analog does not clip, it compresses.

in development.

That's why to be effective, digital needs a more DR than film.

DR is DR.... to use it takes some skills.

Because you will have to sacrifice some of that DR (the part that has
a linear response) to simulate the non-linear portion of film (the
shoulder you had for highlights) and get a smoother transition from
highlights to pure white. Likewise in the shadows with the foot of
the film response.

nice theory, but seems wrong. can you explain the same using
definition of DR as S/N ratio? with numerical examples?

Actually, not wrong. It is just part of the latitude that some film has over digital capture.

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Julia

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