Why don't all companies explain how they test?

[Robert]

I'm looking at the Ilford FP4 + PDF and it mentions the speed is based on ID-11 in a spiral tank. Why can't all the film companies tell us how they come up with thier numbers? I understand the Ilford numbers aren't ISO but it would be nice if they gave us real world numbers.

 

[bmac]

Do you honestly think that you are going to recreate exactly the same conditions as the manufacturer does? The times are just guidelines to base your testing on.

 

[Robert]

That's not the point. Knowing that they're using a certain developer means you can judge how real the numbers are. If they claim a certain EI or other result using a special in house developer then what good is that? It's nice to know how something is tested. Even if you intend to test it yourself later.

 

[bmac]

ID11 is basically Ilford's version of D76.

 

[Les McLean]

Robert,

I appreciate your concern re having an idea of how numbers are arrived at. To give you an idea of how Ilford work, I am one of about 10 working photographers who are given pre production materials to use in our everyday photography and then write a report on how we rate it. Generally we are not given any information as to the characteristics of the product so we have to work it out for ourselves by testing. For example, I had Delta 3200 about 12 months before general release and did all sorts of daft things with it including rating at to 25,000 ISO just to see what would happen. The results where interesting and I now ocasionally use that rating to achieve the effect that I like. I'll post an image I made in a New York underground station with a test batch of the film to let you see the result.

I do not have access to densitometers etc but test in my own way to work out the best speed etc for myself. Certainly, Ilford listen to those of us who test in this way although I cannot speak for other companies. I hope that this posting gives you some understanding of what goes on behind the scenes.

 

[avandesande]

Any of Kodak's time/density charts include developer and temperature information.

 

[David A. Goldfarb]

True, but Ilford's tech sheets are really exceptional in the way they do real-world testing and give practical advice to provide a good starting point for beginners or advanced darkroom workers (for fine grain, try this combo; for more contrast try this one; best acutance with another; higher film speed with another, etc.). If you know how to read the curves and know what the tradeoffs are (how many people really know what their target Zone VIII density is or that fine grain with a solvent developer might come at the expense of acutance?), you can get some of the same information from the Kodak data sheets, but for beginning and intermediate B&W photographers, these intuitive descriptions in everyday language are much more useful. Ilford is also good enough to publish information about results with developers they don't make themselves, which Kodak tends not to do.

 

[john_s]

Some of Kodak's instruction documents are old and could do with some updating. But recent ones, for example the Xtol pdf, have lots of info about other manufacturers products. Some of it looks very interpolated, extrapolated and normalized, though.

I'm not sure about Ilford's approach to film speed. I normally expose Tri-X at 200 and HP5+ at 200, so it's six of one and half a dozen of the other if you ask me.

I do agree that Ilford's lists of strengths (and implied deficiencies) of a range of developers is excellent. With other manufacturers' info you need to read between the lines to get similar information.