What does Dynamic Range Mean?

[Michael Heald]

Hello! I've seen Dynamic Range discussed from time to time in various settings/forums, and I wonder if I understand the term as it is now being used. Most seem to define DR in the way Adams did - each zone is 2x the previous light level. A DR of 10 zones or stops would give a DR of 3 (log10).

The new DSLRs have been quoted as having 8.5 stops or zones (or there abouts) of DR.

Trannies have been quoted as 5.

Film with 6 to 7.

B&W anywhere from 8 to 19, depending on film. I saw the 19 quoted for TMax.

Are these numbers reasonable? I appears that digital has a better DR range than film for tone, and B&W far superior to all. Best regards.

Michael A. Heald

[Bruce Watson]

Hello! I've seen Dynamic Range discussed from time to time in various settings/forums, and I wonder if I understand the term as it is now being used. Most seem to define DR in the way Adams did - each zone is 2x the previous light level. A DR of 10 zones or stops would give a DR of 3 (log10).

The new DSLRs have been quoted as having 8.5 stops or zones (or there abouts) of DR.

Trannies have been quoted as 5.

Film with 6 to 7.

B&W anywhere from 8 to 19, depending on film. I saw the 19 quoted for TMax.

Are these numbers reasonable? I appears that digital has a better DR range than film for tone, and B&W far superior to all. Best regards.

Michael A. Heald

There are some competing concepts here I think. There's the scene brightness range (SBR) where your Adams reference applies. Looking at a scene, zone to zone variance is a factor of two.

Then there is the mapping of the SBR into the capture range of the capture device. I'm not sure of the terminology for digital capture, but with film you convert the SBR into a density range.

For modern films there are two options. Transparency films have a high gamma (contrast index) and therefore use more density to represent each zone in the SBR. This makes tranny films density limited. I'm not sure exactly what the limits are so for the sake of the discussion lets call it 3.6 (that's as far as the Kodak density test target goes). Depending on the gamma or CI of the tranny film in question, it might be able to fit 4-6 stops of SBR into it's density range.

Color negative films and B&W negative films have considerably lower gammas (CIs) and therefore use considerably less density to represent each zone of SBR. Modern color negative films can perhaps go as far as 10-12 stops of SBR before they start to shoulder at the top of their characteristic curves. B&W negative films can go even farther.

That said, when I think of the term "dynamic range" as applied to image capture, what I'm thinking of is the capture medium's ability to capture SBR. That is, how many stops of SBR can the medium capture without shouldering or clipping?

[Scott Knowles]

The new DSLRs have been quoted as having 8.5 stops or zones (or there abouts) of DR.

That's yes and no. At the lowest ISO (50-100) and no plus-EV adjustment under some conditions, yes, but it falls off to a practical range of 5+ at higher ISO and/or with EV adjustment. Or at least by the basic tests I've run on my Canon 5D. And it was stated by a professional at a workshop who uses Nikon highend DSLRs. It's why they teach students to take mulitple exposures, usually 2-3 to get the full shadow and highilght details, to capture the full range and layer your image.

[Michael Heald]

Hello! Thank you for the replies.

It would appear, then, that digital has the ability to capture more stops/tones than trannies, however, the detail of 4x5 would far exceed digital.

I have not heard that color negs have 8 stops. This would be a good reason to shoot negatives instead of trannies. Can you suggest where I can get more information about tone capturing ability of modern films, say Fuji 160 and compare that to, say, Velvia?

Of course, nothing beats B&W for tone. That is what B&W is designed to do! Best regards.

Michael A. Heald