Quick dev question

[PaulJohn]

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I've just come across this

 

"I have used XTOL 1:2 and Rodinal 1:75 with good success. XTOL yields excellent speed with Delta 100."

 

what does it mean by excellent speed?

 

Paul

[pico]

I've just come across this

 

"I have used XTOL 1:2 and Rodinal 1:75 with good success. XTOL yields excellent speed with Delta 100."

 

what does it mean by excellent speed?

 

Kodak's claim to 'Full Film Speed', and reports by users have similar claims including better shadow density w/o clogging nominal highlights. But we know one has to use it to decide for himself.

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[PaulJohn]

Sorry I don't know what 'full film speed' means either.

[becker]

I think that means that films do not reach their nominal speeds fully, a 100 is a 80 Asa a 400 is a 300 …… except

You push them ore change the dillution, temperature, agitation. Thats why I mostly use max two kinds of Film and one kind of developer-

Edited July 25, 2017 by becker

[PaulJohn]

Ahhh, I didn't know that. So some films developed at the claimed speed are actually being pushed from a lower speed. 

 

I've just done some searching and found opinions on the true speed of various films and this varies depending on developer.

 

Light bulb moment!

 

Thank you.

[oldwino]

Rodinal tends to work best with some overexposure (metering at a lower ISO than what the box says). Xtol is pretty much right on the stated speed. Diafine likes underexposure around 1 stop (depends on the film).

[pico]

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Ahhh, I didn't know that. So some films developed at the claimed speed are actually being pushed from a lower speed.

 

B&W film speed is determined for tungsten light. That's a clue to the ISO flub.

[adan]

Percentage-wise, I don't think I have ever seen so much misinformation in a single thread (except on some political sites that shall remain nameless).

 

1. Film speed is not determined for tungsten light. Sorry, Pico, I love ya, but this is just not correct. Now, some B&W films do have extended red sensitivity (e.g. the defunct Kodak TMax 3200, or the old High Speed Recording Film) to help them out under red-yellow tungsten light, but across the board, most films have their ISO determined for a full solar spectrum ("white" daylight).

 

2. Film speed is measured by a complex method set by the ISO (International Standards Organization). Film manufacturers can deviate a bit from the "standard" (e.g. Ilford specifically states that their own method does not use the ISO standard - a given amount of shadow density above "film-base-plus-fog" - but rather the overall density and contrast of a test negative.

 

3. "Full" film speed means the greatest amount of shadow detail/density in a negative of normal contrast. It is the exact OPPOSITE of pushing - which means UNDERexposing (LACK of shadow exposure and detail) and then recovering the mid-tones and highlights with OVERdevelopment to get a usable overall density, with extra/excess contrast. But "pushing" (except as mentioned below) will always mean thin, detailess shadows and a more-than-normal contrast range to the negative.

 

4. Specific to PaulJohn's original question, some particular developers are chemically engineered to produce the maximum amount of shadow detail/density/amount of silver in the shadows, for a given exposure. Or "Full film speed" as the ISO defines it - WITHOUT getting the excess contrast from "pushed" overdevelopment.

 

(Keep in mind that developers are not a single chemical, but a mixture of about half a dozen chemicals that do different things in the developing process, and by fiddling with the proportions, their behavior can be tuned to bias for: fine grain, maximum film speed, "compensating" effects, minimum amount of "fog" (i.e. silver "exposed" by the developer itself, not by light).

 

A developer that delivers "full film speed" usually does one or more of the following.

 

1. It has a compensating effect - between agitations in the tank, the developer "poops out" rapidly in the highlights where there is lots of exposed silver to react with, giving the highlights less development, while chugging right along in the shadows to develop every bit of exposed silver. Result, more density in the shadows, without excess density (contrast) in the highlights.

 

2. It may have a reduced amount of silver "solvent" - a chemical (usually sodium sulfite) that dissolves or eats away at the silver being developed even as it is being developed. Which produces less grain, but also less silver, and thus less film speed. (NB. sodium sulfite is also an anti-oxidant that preserves the developer over the weeks it may be sitting unused - just as sulfites are used to preserve wines, so most formulas have at least some, but the less used, the more film speed (and grain) you'll get, and the more used, the finer the grain (and the less film speed) you will get.)

 

Indeed, XTOL developer is one of these "full-speed" developers. So is Ilford Microphen and to a lesser extent Ilford DDX.

 

Compared and contrasted with my own favorite, Kodak HC-110, which tends to lose about 1/3rd stop of shadow density, but is finer-grained. Or Microdol-X, with a ton of sulfite, which loses a full stop of "box" film speed, but is very fine-grained.

 

If you MUST "push" film to an exposure index above its nominal ISO speed (e.g. Tri-X ISO 400 pushed to EI 1600) for reasons of stopping action or low-light overall, a compensating developer will give the shadows as much density as possible (but still woefully less than exposing at 400). Thus developers specifically intended for pushing, with a strong compensating action (Diafine, or the others mentioned above) are the best ones to use.

 

5. So - the ISO test for film speed is based on amount of shadow detail. Delta 100 should have usable detail in shadow areas that are about 3-4 stops darker than a medium gray. Depending on the developer used, you may get usable shadow detail in areas 3-4 stops darker than medium gray at:

 

ISO 100-125 with developers that deliver "full speed."

ISO 80-100 with general-purpose developers

ISO 50 or so with "fine grain" developers.

Edited August 7, 2017 by adan

[pico]

Film speed is not determined for tungsten light. Sorry, Pico

 

I've been fostering my error for decades. I wonder where I picked that up. Maybe in film school?

Thank you for the correction.

[adan]

Film School as in motion pictures? - could be.

 

The default color film in motion pictures is balanced for tungsten (all those floodlights on set) and filtered when used under daylight, so the "base" ISO for those films is usually calculated for tungsten just like the color. Even B&W films in Hollywood have to be metered according to their tungsten sensitivity

 

At least, once upon a time in Hollywood:

 

http://theredlist.com/media/database/films/cinema/1950/sunset-boulevard/082-sunset-boulevard-theredlist.jpg

[pico]

Yes, for the early days of B&W motion pictures it is interesting to read of pancake and orthocake makeup... unless my memory is wrong again. (Such lapses seem to be more common in old age.)

[tobey bilek]

Box or nominal film speed is done by a strict ISO standard test using D76.   Other times and developers yield different results.   

 

I find Kodak & Ilford times perfect and they print controlled tests on #2 paper.   Massive Development Chart time sometimes all over the map.  Some not even a good starting point.

 

Developers give high speed, sharpness,  and fine grain.  Pick any two.  NO developer does it all.

 

Use what you read on internet with caution.  Some people do not know what a print is supposed to look like, and other have thermometers or camera meters or shutter speeds that are off.  You must have calibrated equipment.

[Jeff S]

Some people do not know what a print is supposed to look like, and other have thermometers or camera meters or shutter speeds that are off. You must have calibrated equipment.

The goal isn't to calibrate the gear to some standard; it's to use that gear effectively to create predictable and reliable results. The key is to run tests, and establish consistent practices, with one's own and distinct cameras, shutters, thermometers, and other gear and conditions to facilitate predictable and desired print results (tonal values for b/w). It's in large part because all these factors vary... from gear to gear and person to person...that standardized tests can prove useful.

 

I agree that the hardest part is to know what a great print should look like. Densitometers and such can measure tonal differences, but only the eye and brain can determine when, where and to what degree to use those tones for best effect. Film speed, development time and print tests can be easily taught.....having a good eye and judgment is indeed the hard part.

 

Jeff