What's the dynamic range of B&W film?
Anyone know the dynamic range of B&W films like Tri-X, BW400CN and XP2 Super? And how does one maximize the huge dynamic range properties of B&W film?
Maximise the contrast of the subject, exposure,
Originally Posted by film_guy
and development. Dan
Tri-X probably has the biggest range of the three.
You don't need to maximize the whole dynamic range of B&W film unless you have a high contrast subject. With normal development, you should have full detail from zone 3 through zone 7, or 5 stops, using B&W film, and retain textures in zones 2 and 8 -- so that's about a 7 stop range with normal development. But if you're willing to pull 2 stops in development, then you can capture detail over a 9 stop range. And if you read about people like Bruce Barnbaum who use extreme compensating developers, you can pull like 7 stops and capture detail over a 14 or 15 stop scene brightness range (which one hardly ever encounters).
The best way to make sure you maximize the DR of B&W (and color print) film is to make sure you don't lose shadow detail. Survey your scene, place important shadows on zone 3, and then adjust development to place important highlights on zone 8. That's a fairly simplified zone system, and it takes advantage of the film's DR.
Does using a divided developer like Barry Thornton's 2-Bath buy you anything?
Also how much of a gain do you really see from a 'full speed' developer like Xtol or DD-X over something like D76?
I'm assuming by dynamic range you mean the range of tones between pure black and pure white (which, in ZS terms would be negative densities that yeild print tones from Zone I to Zone IX). I would say that it is maximized when the negative is developed to a contrast range that is closely aligned with the exposure scale of the paper you are using.
Straight line films today may not reveal a shoulder on the curve until a log E density of 3.3 (Zone XII) or more. Even so, you must hold the negative density range to within the printable density range of the paper. The capabilities of the film is buffered by the limitations of the paper, so you must maximize the capabilities of the paper by careful exposure and development of the film.
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How much dynamic range? It's kind of like asking, "How big is a rock?" It is very difficult to quantify film performance in the way people have come to expect from being exposed to the marketing claims on the boxes that contain certain types of imaging hardware.
We test so allot for specific situations because film possesses such a wonderful range of responses under different conditions and procedures, so in order to answer your own question you would have to have a particular exposure and developing regimen in mind for a specific stock.
In general one can state certain properties that a particular stock may posses under general circumstances, but if you are looking for a specific answers, you need a specific protocol, and getting that answer requires carrying through with that procedure, unless you are lucky enough to be in contact with someone who already has, and even then, YMMV.
The short answer regarding the dynamic range of B&W film is "usually more than most persons can print"
Last edited by JBrunner; 11-29-2007 at 10:25 AM. Click to view previous post history.
A simple BTZS test will answer your question about most any B&W film you are interested in.
Originally Posted by film_guy
Chuck is certainly headed in the right direction.
The range of the films today are far greater than the papers most people use. It doesn't matter if the film has a tremendous range if the papers can not reproduce it.
That is the reason many workers print on Pt/Pd, albumen, salt and so on - they are able to produce a far greater range than silver gelatin.
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Dynamic range must be defined before it can be used. The ancient philosophers had a rule: define your terms. I saw several posters apparently using several definitions.
When you photograph a scene, you are trying to capture a certain range of scene brightness in such a way that you can display it on paper or on a screen. All transparent materials can show by transmitted light a scene of much wider range than can be shown realistically on paper. If you are planning to print on paper, it does little good to capture a scene brightness range that is much greater than paper can show. We can fool the eye to some extent, as painters have been doing for eons, but by and large the maximum brightness range film can possibly record depends on its maximum density. The maximum range in practice also depends on the developer. The same film will have a different maximum gradient in each developer and concentration. HP5+ in Rodinal at 1+50 dilution cannot achieve a gradient greater than 0.61 according to AGFA. I don't remember what its maximum density is, but let's say it is 3.0. A rough guess at its maximum scene brightness range would be 4.9 log units. The actual brightness ratio would be greater than 75000 to 1.
Now the question is how to extend that range. If the maximum density the film can provide is 3, we do NOT want to jack up the contrast by choosing a different developer. That would cause a shorter brightness range to use up all the film's density range. If you are hell bent on extending the scene brightness range you can record, you could develop to a CI of 0.3 and stretch it out to about 10 log units. Where you will get such a scene to photograph I do not know and probably would rather not know.
Paper can show a maximum reflection density on the order of 2 log units.
Yikes, can someone explain in layman's terms to me about all the technical terms spoken here? lol
Thanks guys for the thorough explanations, although I understood only 1% of what's being talked about.
Another question - if I use BW400CN or XP2 Super, and have a lab develop them, I guess I'm at their mercy when it comes to wanting prints with high dynamic range?