How many stops available in B&W film?

film_guy · Mar 9, 2007

How many stops is realistically possible on B&W film like Tri-X or HP5 Plus or chromogenics like XP2 Super or BW400CN?

doughowk · Mar 9, 2007

Bruce Barnbaum, in his Art of Photography book, says B&W film can have as much as 12-15 stops of usable information. Not sure about the specific films you mention.

Roger Hicks · Mar 9, 2007

film_guy said:
How many stops is realistically possible on B&W film like Tri-X or HP5 Plus or chromogenics like XP2 Super or BW400CN?

Do you mean density range (which varies widely from film to film) or information recording range (which depends on the slope of the d/log E curve)? If the latter, the answer is at least 10 stops with most films under most normal conditions and a lot more with minimal development in ultra-low-contrast developers.

The big question is how much usable information is there, and this depends on what you are using it for: pictorial photography is rather different from solar eclipse photography, for example.

I'm not sure it's an outstandingly useful question, except insofar as it gives a rough idea of what is and isn't possible - a bit like the thread on the maximum resolution possible on 35mm film.

Cheers,

R.

bwakel · Mar 9, 2007

I'm not sure of the reason for the question but it's interesting comparing the dynamic range that I can extract from a negative using my Nikon Coolscan LS9000ED scanner compared with a darkroom print. The Coolscan is fine for scans of Velvia but runs out of dynamic range on monochrome scans with fine highlight details. I think the scanner can manage about seven stops and most of my Velvia transparencies are around five stops. Prints created from the same monochrome negatives show highlight details going on for several more stops so I'd agree that there are at least ten stops of usable detail in a normally developed and printed negative.

Barry

Ole · Mar 9, 2007

With careful attention to exposure and processing (or just a lot of luck), my experience is that some "traditional" films can handle at least 17 stops.

noseoil · Mar 9, 2007

You won't really see the dynamic range of B&W film which is possible, until you start doing your own development. With today's developers and an understanding of contrast in film and printing, you should be able to bring out details which would seem impossible with "normal" development or lab processed film. Take a look at Sandy King's recent uploads and think a bit about the contrast range he was working with, to make the two prints. tim

Photo Engineer · Mar 9, 2007

In measurments I have made with an ISO 100 film, it yielded good prints from a value of 25 to 400. The main change was in grain, with some sharpness change. There was some change in highlights and shadows but not as much as I expected.

My opinion is that films have about 5 stops usable range.

PE

Donald Miller · Mar 9, 2007

I think that before you can come up with a valid number you must determine the process that you are going to be printing. Beyond that thinking in terms of stops is like asking how many chickens can you get in your truck. That depends on the size of the chickens and the size of your truck. It is more valid to think in terms of the density range that a given film can hold.

gainer · Mar 9, 2007

A lot more usable information can be put on film than you can use to make a good print without dodging/burning. Generally, that much information cannot be contained in light coming from a single feflective surface. That is limited by the ratio of reflectivities from about 0.1 to 0.9, about 5 f-stops from pure black to paper white. A problem arises when you want to photograph what a person would see when, say, looking out a window where detail inside the room and outside the window are seen clearly due to the adaptivity of the eye. A scanning camera could be made that would do the same, but who among us has one of those? The painting artist can approximate that to good effect. The film-camera can record all the necessary data, but a simple straight print will not. A possible exception is a print made on printing-out paper, which can be self-masking due to the fact that density built up in the print's shadows slows the rate of accumulation of density in the those areas.

Photo Engineer · Mar 9, 2007

The average range of reflective density is 0.1 to 1.9 or 2.2 depending on surface. But the range of the image is the contrast of the film x contrast of the paper used. This is, on average 0.6 x 2.5 = 1.5 for the mid scale contrast of the final print.

PE

Sirius Glass · Mar 9, 2007

Photo Engineer said:
The average range of reflective density is 0.1 to 1.9 or 2.2 depending on surface. But the range of the image is the contrast of the film x contrast of the paper used. This is, on average 0.6 x 2.5 = 1.5 for the mid scale contrast of the final print.

PE

Please translate this to range f/stops that B&W film can handle. :confused:

Steve

Photo Engineer · Mar 9, 2007

Steve;

I already did in my first post. Exact ISO numbers from over to under exposure for an ISO 100 film.

PE

Helen B · Mar 9, 2007

bwakel said:
I'm not sure of the reason for the question but it's interesting comparing the dynamic range that I can extract from a negative using my Nikon Coolscan LS9000ED scanner compared with a darkroom print. The Coolscan is fine for scans of Velvia but runs out of dynamic range on monochrome scans with fine highlight details. I think the scanner can manage about seven stops and most of my Velvia transparencies are around five stops. Prints created from the same monochrome negatives show highlight details going on for several more stops so I'd agree that there are at least ten stops of usable detail in a normally developed and printed negative.

Barry

Barry,

You might like to raise that issue over on hybridphoto.com because it sounds like you have a problem that could be solved.

Best,
Helen

Lee L · Mar 9, 2007

Stever said:
Please translate this to range f/stops that B&W film can handle. :confused:

Steve

Reflective and transmissive density are measured in units where a change of 0.3 equals one stop. So 0.10 = 1/3 stop, 0.60 = 2 stops, etc. When someone gives you a number like 2.2, just divide by 0.3 to get the number of f-stops. Optical density numbers are easier to deal with and pretty easy to get used to.

You can calculate this by taking the base 10 log of a number. Let's say you have 4 stops difference in reflectance or transmission. That's a factor of 2^4, or 16. The base 10 log of that factor of 16 is about 1.204119983, or round to 1.2 log density units. Divide by 0.3 and you get 4 stops.

Lee

Photo Engineer · Mar 9, 2007

And, to use Lee's example, and the one I gave, the range from ISO 25 includes 50, 100 (published ISO), 200 and 400 which gives an effective 5 stop range. I would only use 3 of them practically, 50, 100 and 200 in a pinch. Overexposure is preferred to underexposure for negatives.

PE

Donald Miller · Mar 9, 2007

The thing that I would add to what Lee L and PE said is that while density is given in log units, it is important to remember that no photographic material (be that film or paper) is linear in it's response to light exposure. Thus a negative that evidences a density of 1.35 (TD) may, and probably will not, represent a 4 1/2 stop exposure scale. It may represent three stops as easily as any other value...depends on the initial exposure placement and the development given to the material.

Sirius Glass · Mar 12, 2007

I will restate my question.

The statement was made that 100 ASA film has a range of 25 to 400 ASA => 4 stops, but that only states the range of the exposure and not the latitude of the exposure.

If, for the sake of this discussion, [as an example, say] at 25 ASA the film spanded from five stops below and to five stops above, and at 400 ASA the film spanded from four stops below and to six stops above, then the exposure latitude would be 5 + 4 + 6 = 15 stops.

So, again, in stops, what is the exposure latitude of black and white film?

Steve

Donald Miller · Mar 12, 2007

Stever said:
I will restate my question.

The statement was made that 100 ASA film has a range of 25 to 400 ASA => 4 stops, but that only states the range of the exposure and not the latitude of the exposure.

If, for the sake of this discussion, [as an example, say] at 25 ASA the film spanded from five stops below and to five stops above, and at 400 ASA the film spanded from four stops below and to six stops above, then the exposure latitude would be 5 + 4 + 6 = 15 stops.

So, again, in stops, what is the exposure latitude of black and white film?

Steve

You seem to be asking a question to which there is no definitive answer. First of all there are ISO 25 films and there are ISO 400 films but there are no films that are ISO 25/400. Every film has a defininite speed and while we may attempt to expose it under less than optimal conditions, it will yield less than optimal results when we do so.

Second you seem to be thinking that all films are characteristically the same. That simply is not the case. Each emulsion has it's own characteristics. That means that HP5 (Ilford) has a different characteristic curve that Tmax 400 (Kodak). Furthermore TriX has different characteristics than Tmax 400 even though both come from the same manufacturers.

To continue, a film like Bergger BPF 200 will have a maximum density range of approximately 1.75 ...in other words that is all the hell you are going to get out of the film even though you develop it for seven sundays from now. While another film Efke Pl 100 will develop to a density range above 2.30 when developed for 58 minutes in minimal agitation using Pyrocat HD 1-1-150.

So you can restate your question as many times as you wish and you will not arrive at a definitive answer until you provide more information like which film, which developer, at what exposure, and for how long?

To further complicate this matter, one must determine not how much latitude a black and white film has but how much scale the printing material has because it serves no purpose for a film to have a gazillion stops of latitude if the darned paper will only hold five or six stops (depending on grade).

I hope that this finally puts your question to rest.

Photo Engineer · Mar 12, 2007

Steve;

If you properly expose and develop a negative film, you will use the entire 'latitude' of the film which is whatever the manufacturer built into it. This can be up to 21 steps of information, in increments of 0.1 log E, when measured in terms of density information vs exposure.

It can be more but common films are not manufactured with this capability. This about 10 stops total, but usually averages out to 7 stops. That agrees with the zone theory which is merely a generic method of describing basic H&D or sensitometric curves.

Now, even though that informaiton is recorded, only the central portion can be printed due to the fact that a normal print material has a contrast of 2.5. This limits the printable latitude considerably but actually results in a usable print.

In simple terms, there is one usable center point and 3 points on either side of that to total 7 usable center points. One is correct, and 3 over and 3 under. The over are better. One on each side place you into the toe and shoulder which sacrifice either shadow or highlight details due to the rollover of the film curve.

Does this help any more? If not, I would have to resort to some hand drawn curves.

PE

Sirius Glass · Mar 12, 2007

Photo Engineer said:
Steve;

If you properly expose and develop a negative film, you will use the entire 'latitude' of the film which is whatever the manufacturer built into it. This can be up to 21 steps of information, in increments of 0.1 log E, when measured in terms of density information vs exposure.

It can be more but common films are not manufactured with this capability. This about 10 stops total, but usually averages out to 7 stops. That agrees with the zone theory which is merely a generic method of describing basic H&D or sensitometric curves.

Now, even though that informaiton is recorded, only the central portion can be printed due to the fact that a normal print material has a contrast of 2.5. This limits the printable latitude considerably but actually results in a usable print.

In simple terms, there is one usable center point and 3 points on either side of that to total 7 usable center points. One is correct, and 3 over and 3 under. The over are better. One on each side place you into the toe and shoulder which sacrifice either shadow or highlight details due to the rollover of the film curve.

Does this help any more? If not, I would have to resort to some hand drawn curves.

PE

Yes. My comments about 25 to 400 ASA were refering to the statments that 100 ASA films can be exposed from 25 to 400 ASA.

Now back to your comments. At Kodak, I was told [informally, not a company statement] that print film latitude of expose was about 10 stops and under ideal conditions [rarely] could get as high as 12 to 14 stops. Slide film was closer to 4 stops. This is roughly corresponds to my experience => with slide film one must be accurate with the exposure, but print film will allow you to pull out a good print with shadow detail from an exposure with a wide range of "sins".

So I think we are in violent agreement on this.

In the D__________l world the exposure latitude seems to be three stops and shadow detail is lost forever.

Steve

Photo Engineer · Mar 12, 2007

Steve;

Digital acts like a reversal film with poor or no latitude.

PE

Paul Howell · Mar 12, 2007

Which is why I have a 12mp DSLR and get better prints with C41 and my 35mm.

vet173 · Mar 12, 2007

I think Film guy left after Ole answered his question.

Sirius Glass · Mar 12, 2007

Paul Howell said:
Which is why I have a 12mp DSLR and get better prints with C41 and my 35mm.

Without the range in the color gamut, without the exposure latitude, without the archival life, without the protection on the environment, ... [this is a really l-o-n-g list]

Steve

Photo Engineer · Mar 12, 2007

Steve;

A friend of mine formerly of Kodak research has a booklet on the reasons with the entire proof. His talk on this at ICIS last year was cancelled "due to lack of interest". There are so many reasons why digital is not as good as analog.

However, the use of analog for the original, and digital for the prints does allow for very high quality. I feel that digital prints are very close to analog prints. However this does not address a whole host of problems. One of the leading ones, image smear, has been virtually ignored in the industry. Overall image stability is not as good as analog, except for digital pigment prints.

PE

How many stops available in B&W film?

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