Exposure latitude in film

[mdarnton]

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You have not understood a bit of what I said. I am NOT talking about the scene, I'm talking about the piece of film in front of us, which has its own dynamic range, independent of the scene. Please go back and try it again.

 

It may be the case the way you work, but black is black whether a slide or a negative and I can assure you that photographers have managed to achieve 'black' from negatives throughout history. If only he was alive you could try telling Ansel Adams that he can't get a good black.

 

The assertion that the slide has a wider dynamic range than a negative is fundamentally flawed. The dynamic range of slide film is set in the characteristic's of the film, it can only deal with a limited range dictated by the emulsion and the E6 processing which can't be adjusted. So a scene that goes from intense highlight to the deepest shadow will be truncated at one end of the range or another, and is the reason that slide film is generally recommended to be slightly under exposed. The fact that you see the deep black that you like is because the film has given up as much as it can, it has fallen off the cliff. B&W negative film on the other hand (if we forget for one moment your assertion it has a smaller range) can be exposed with the development pre-planned to mimic the tonal range of the same high range scene, or to compress the tonal range. The 'black' that you seem to see as a definition of a wide dynamic range is a very tiny proportion of a typical landscape scene for instance, intense black does not normally appear in nature, yet I will agree with you that it does often appear as a characteristic of slide film, because it has a limited dynamic range, not because it has a wide dynamic range.

 

Steve

[AlanG]

You have not understood a bit of what I said. I am NOT talking about the scene, I'm talking about the piece of film in front of us, which has its own dynamic range, independent of the scene. Please go back and try it again.

 

While slide film can have a higher D-max than negative film, that does not mean it can record detail in a scene that has a greater brightness range. The reversal process limits it on the highlight end and to maximize range you'd have to underexpose and try to pull out detail from the shadows. At that point you may struggle to make a print or good scan and also may run into what is called "crossed color curves." I once made a Cibachrome from someone's dense slide that required a 20 minute exposure in my enlarger. It came out better than I expected and had an interesting look but in no way matched how a "properly exposed" image would have printed.

 

Whereas with a b/w negative on a double coated film you can get quite a few steps of detail into the highlights while still preserving shadow detail. You can often recover all of this detail by making a contrast mask, burning in, using special scanning techniques, using a Log Etronics enlarger, etc. This compresses the variation in white to black steps down to a range that can be reproduced in a print. So now your 10,000:1 brightness range scene (about 13 stops) gets "interpreted" as a 100:1 (about 6 stop) range of a glossy print.

 

A lot of what has been posted is off topic from the subject of latitude. Latitude comes up when your scene will fit within the detail part of a film's characteristic curve with some room to spare. Whatever the film. All that matters is what is the shape and range of this curve and what is the brightness range of the scene you have. If you have a scene that uses up all of the film's range, you have very little latitude in exposure and must be careful where you place the first tone that requires detail. If the scene has a low brightness range that only uses up some of the film's useful curve, then you don't have to be as careful about where you place the exposure to get a "useable" print.

 

The amount your exposure can be "off" is the measurement of latitude. But this is just a general term and only has meaning for a given scene/film/development combination that also depends on what you consider to be an "acceptable" print.

[250swb]

You have not understood a bit of what I said. I am NOT talking about the scene, I'm talking about the piece of film in front of us, which has its own dynamic range, independent of the scene. Please go back and try it again.

 

I admit, I haven't understood much of what you say, but if an exposure can't be equated to something real, a scene, a test card, a development process, then I fail to understand how the film can have a dynamic range or latitude. It is the same sort of philosophical question as 'does a falling tree make a sound in the forest if there is nobody there to hear it'.

 

There is no inherent range for a B&W film because there are no standards by which exposure and development are judged other than empirically. Every film has a different range and latitude in every different type of developer, never mind the varied ISO rating's and exposure choice's. True there are manufacturer's guidelines, but these are to get you started, they simply suggest a ballpark. Nobody actually makes the same exposure that the manufacturer made though, and nobody has to agree with the manufacturer if the contrast range they want is different. I think you have a fundamental misunderstanding of both latitude and dynamic range, the photographic language and concept's you use are quite unlike any I have ever heard before, and that's saying something. And no, I won't be lectured to 'go back and try again'.

 

Steve

[pico]

A subject not discussed is the luminance range of B&W printing paper.

 

Have all abandoned printing?

[chris_livsey]

A subject not discussed is the luminance range of B&W printing paper.

 

Have all abandoned printing?

 

Presumably you mean sensitised paper

[AlanG]

A subject not discussed is the luminance range of B&W printing paper.

 

Have all abandoned printing?

 

I said a glossy print can handle a brightness range of around 100:1. (More or less.) If you aim a bright spotlight at it you can maximize its range. A matte print has less range of course. So whatever your original scene, it needs to fit within this somehow.

 

Every technical aspect about film, paper, and processing was studied, measured, and analyzed long ago. It is well documented in countless books. You can look it up.

[pico]

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I said a glossy print can handle a brightness range of around 100:1. (More or less.) If you aim a bright spotlight at it you can maximize its range. A matte print has less range of course. So whatever your original scene, it needs to fit within this somehow.

 

Every technical aspect about film, paper, and processing was studied, measured, and analyzed long ago. It is well documented in countless books. You can look it up.

 

Oh, Allen I know that. I was posting in part to ferret out optical wet printers from scanners-to-screen and scanners-to-cats-spray persons.

[CalArts 99]

Donno what php stands for, I typed 3 yellow smileys, as for yes! Pico, please do.

 

I use pyro (Pyrocat) with sheet film.

 

Here's an overview that will give you plenty of info about these sorts of developers and a full history: An Intro to the Pyro Staining Developers - Sandy King Photography

 

And this website is Pyrocat HD centric but there are numerous links to all sorts of information about using staining and divided developers: Pyrocat HD

 

Bear in mind that pyro is toxic (skin contact and breathing the powder) and should always be used wisely.

[mdarnton]

I admit, I haven't understood much of what you say, . . And no, I won't be lectured to 'go back and try again'.

Steve

 

I have to admit I'm not in your position of understanding everything already, and being able to immediately reject things I don't get as being nonsense. When I come up against that, I dig back in and try harder. Nevertheless, I assure you it makes sense, if you can sort it out.

[Guest]

I use pyro (Pyrocat) with sheet film.

 

Here's an overview that will give you plenty of info about these sorts of developers and a full history: An Intro to the Pyro Staining Developers - Sandy King Photography

 

And this website is Pyrocat HD centric but there are numerous links to all sorts of information about using staining and divided developers: Pyrocat HD

 

Bear in mind that pyro is toxic (skin contact and breathing the powder) and should always be used wisely.

Always looked up to your posts here for the competence based on a life-long practical experience with a well-read background

But I have my doubts now for a moment: isn't the wisest way to use something toxic to simply avoid it?

So are there alternatives? Less hazardous chemicals?

[250swb]

[/b]

Always looked up to your posts here for the competence based on a life-long practical experience with a well-read background

But I have my doubts now for a moment: isn't the wisest way to use something toxic to simply avoid it?

So are there alternatives? Less hazardous chemicals?

 

Do you drink household bleach? Do you overdose on paracetamol? Of course not, and pyro is only a similar hazard.

 

But for safer alternatives to pyro developers you can try catechol based formula's.

 

http://hypercatacutancedeveloper.blogspot.co.uk/2012/07/obsidian-aqua.html

 

Steve

[CalArts 99]

[/b]

Always looked up to your posts here for the competence based on a life-long practical experience with a well-read background

But I have my doubts now for a moment: isn't the wisest way to use something toxic to simply avoid it?

So are there alternatives? Less hazardous chemicals?

 

For a true pyro staining developer there is no way out of the fact that pyrogallol is a toxic chemical. And so yes, the wisest thing is to avoid it if one doesn't feel comfortable with taking any risks and which is precisely why I added the warning. But I was adding the warning specifically about pyrogallol in general and not Pyrocat itself. PyroCat is a catechol formula and is indeed an alternative to pyrogallol developers. But the poster I responded to was asking about staining and dividing developers in general. I only mentioned that I used Pyrocat as a pyro type of developer, although in fact it's not quite the same. It's an alternative to pyro. So I suppose it is somewhat misleading to have said it's a 'pyro' developer (although it acts just like one.) My apologies on any confusion.

 

Pyrocat is a less toxic recipe since it's a pyrocatechin; see Steve's comment above about catechol based recipes. But of course it still should be used very wisely. Here is the material safety data sheet (MSDS) for Pyrocat HD http://www.pyrocat-hd.com/pdf/FormularyCatecholMaterialSafetyDataSheet.pdf MSDS are reports for using a specific chemical in the American workplace under the US Federal Occupational Safety and Health Administration, in case you're not familiar with these and are outside the US.

 

We have to be careful with pretty much any chemical, for certain. I use Eclipse to clean my camera sensors and Eclipse is methanol which is also very toxic and highly flammable (and it burns with no visible flame.) But I'm making the choice to use it because it works very well. Nonetheless, I'm overly careful while using it.

[Guest]

If I'm not mistaken Ansel Adams and Yosuf Karsh were using also pyro developers, being in their dark-rooms more than a dozen average film users today put together ( including the ones, who get their negatives back from their lab and scan them).

 

May we all reach their age!

 

Thank you very much for ALL your posts CalArts 99

 

Best regards,

Simon

[tobey bilek]

For an ideal print, film has no exposure latitude. The idea you can makeup for bad exposure by changing printing exposure and contrast is false. Yes that is the correction and you do what you have to do, but the resulting print is not ideal.

 

For low contrast subjects, you can slide the exposure up/down a stop or so and it will not be noticeable.