B&W Film Dynamic Range

[marschp]

I started photography in the digital domain, have recently moved to colour transparency, and am now looking at B&W film. My question is, how do I find out info on the DR of different B&W films. I've just trawled the Ilford fact sheets and it doesn't mention DR. I've just got used to dealing with 5 stops of DR on a sensor, and 4 and a bit of DR on Velvia 50 (using NDG's and all that) - and I;ve heard that some B&W films can handle scenes with DR of 10-11 stops (does this mean I won't need to use all my NDG filters?) - but where do I find out specific DR for specific films? Any help would be greatly appreciated.

Paul.

[JW Dewdney]

Actually- of all places - I'd probably recommend Ansel Adams' book The Negative for some of this info. It will probably tell you just about all you need to know on the subject...!

[paulr]

The DR of black and white films is almost infinitely adjustable. A film like TMX can have a range of 2 or 3 stops with an extreme high contrast developer, 10 to 12 stops with normal development, to over 20 stops (1 : 1 million!) with an extreme low contrast, compensating developer like POTA.

The reason "normal" development means 10 or so stops dynamic range is that this has proven most useful for people most of the time--it's a convenient standard, not something inherent in the film itself.

[Ken Lee]

While we are on the subject - Why can't affordable digital cameras (or their sensors) handle a wider dynamic range ?

[Gordon Moat]

Photon collection and charge accumulation. Imaging sensors essentially build a full charge in each pixel well when they indicate a pure white area. A pure black area would basically mean no charge accumulated. As you go from white (lighter areas) to darker areas, there is less charge collected. So darker tones are created from a very low charge accumulation, which is also why Bayer interpolation causes worse problems in darker tones than in lighter regions of a scene/image. Anyway, there are entire books on this stuff, so obviously I am greatly simplifying this explanation.

Ciao!

Gordon Moat
A G Studio

[Bruce Watson]

While we are on the subject - Why can't affordable digital cameras (or their sensors) handle a wider dynamic range ?

What Gordon said. Basically it comes down to the size of the sensor wells and the range of charge accumulation. Bigger arrays take more real estate on the wafer which runs the cost up. More charge accumulation takes a higher quality design, from the wafer to the onboard camera electronics, which also runs the price up. IOW, you get what you pay for.

Historically the price has been dropping as sensor quality has been increasing. I have no doubt that Moore's Law is being confirmed for digital camera sensors. So give it a few years -- eventually the quality/cost balance will be what you want.

But if you are waiting for that $1000 USD P80+ digital back equivalent like I am, you are going to be shooting LF film for quite a few more years

[Bruce Watson]

The DR of black and white films is almost infinitely adjustable. A film like TMX can have a range of 2 or 3 stops with an extreme high contrast developer, 10 to 12 stops with normal development, to over 20 stops (1 : 1 million!) with an extreme low contrast, compensating developer like POTA.

The reason "normal" development means 10 or so stops dynamic range is that this has proven most useful for people most of the time--it's a convenient standard, not something inherent in the film itself.

What Paul said. I saw a report many years ago that said that scientists at Kodak had shown that TMX could deliver something like 20 stops of density information. That is, about 10 stops more than you could print with an enlarger if you were really working at it. The film can do it, but it's not really useful to us because we can't read the information outside the laboratory.

What this means is that dynamic range is difficult to define for modern B&W films. What that means to us is that we are free to use exposure and development to create the density range we want on the film. That density range is limited by the darkroom papers we use, or the scanning system we use. It is not limited by the range of densities of which the film is capable. And that is perhaps the reason no one bothers to publish the dynamic range information you seek.

[paulr]

aparently POTA and plus x were used years ago to capture detailed pictures of nuclear explosions.

[roteague]

I have no doubt that Moore's Law is being confirmed for digital camera sensors. So give it a few years -- eventually the quality/cost balance will be what you want.

Moore's Law has nothing to do with the quality/cost of sensors, it has to do with the size and number of transistors that can be packaged in an integrated circuit; granted quality/cost is a measure of the effectiveness of Moore's Law, but not what defines it.
What is changing is that sensors are moving away from being CCD based to CMOS based, and the processing software is getting better.

[Ron Marshall]

A link to some examples of adjusting b/w development to adjust the density range of the negative to suit the brightness range of the subject:

http://unblinkingeye.com/Articles/PC-HD/pc-hd.html