A Lazy Man's Zone System

[Milpool]

Note: My transcription of the Ilford data sheet curve depends on the published curve being accurate. I divided the exposure axis into ten divisions and then calipered to the middle of the thick curve line at each crossing.

Then I set the speed scale to where the foot crosses 0.1

I didn’t actually process and graph my own results. I am curious to see how that will compare.

Last time I bought a couple boxes of paper the seller included a roll of HP5+, so I will test it sometime soon.

If it helps at all I once ran the test on HP5+ using D-76 and surprise, surprise, ISO 400.

The curves in the Ilford/Harman documents are pretty useless in my opinion. They don’t tell the typical user anything, and aren’t detailed enough for anyone who might be interested in sensitometry.

 

[Stephen Benskin]

I've often pointed out that film speed and exposure are two different things. Too often film speed is conflated with exposure. Most of the discussions about film speed are really about exposure. This is why it's important to be able to measure and control the variables in testing in order to properly attribute the results. Is the thin negative the result of lower than expected film speed in a given developer, under development, or under exposure of the test? Which is why improper testing tends to lead to achieving incorrect conclusions with a false sense of confidence. This raises the question whether it's better to use the manufacturer's testing and make adjustments based on personal results.

 

[Stephen Benskin]

If it helps at all I once ran the test on HP5+ using D-76 and surprise, surprise, ISO 400.

The curves in the Ilford/Harman documents are pretty useless in my opinion. They don’t tell the typical user anything, and aren’t detailed enough for anyone who might be interested in sensitometry.

The Ilford data sheets use relative log exposure, so there's not really much more they can do than give than an impression of the type of curve of the film. In my opinion, a good Gamma-time curve would be more helpful.

 

[pentaxuser]

I don't think it helps for Ilford to call it foot speed, but yes. The data sheet clearly shows HP5 Plus as ISO 400. View attachment 400778

EI refers to the camera setting. Here's the entire paragraph from the data sheet.

EXPOSURE RATING
Best results are obtained at EI 400/27, but good image quality will also be obtained at meter settings from EI 400/27 to EI 3200/36. It should be noted that the exposure index (EI) range recommended for HP5 Plus is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard.

It's saying basically the same thing as with D3200. It has been determined (non-sensitometrically) that acceptable / good results are obtainable if the camera is set to EI X, not that the film speed is EI X. The speed of the film is the ISO and how the camera can be set is the EI. Ilford is using the terms correctly. They could just communicate it better. There always seems to be a compromise between being scientifically accurate and being understood by the general public.

Thanks for the reply but as I said I assume that by now everyone here even relative newcomers understand that there is only one ISO applicable to any film and that all the other speeds quoted in Ilford's sheets are not ISOs

It was just that I had assumed that you might have been saying something different that I and others might have been unaware of

Good to know that it was not something new

pentaxuser

 

[Stephen Benskin]

Thanks for the reply but as I said I assume that by now everyone here even relative newcomers understand that there is only one ISO applicable to any film and that all the other speeds quoted in Ilford's sheets are not ISOs

It was just that I had assumed that you might have been saying something different that I and others might have been unaware of

Good to know that it was not something new

pentaxuser

No, it wasn't something new. I was just pointing out a frequently misinterpreted statement by Ilford.

 

[pentaxuser]

The HP5 document also refers to the ISO speed:

Although rated at ISO 400/27º, HP5 Plus can produce high quality prints when exposed at meter settings up to EI 3200/36 and given extended development in ILFORD ILFOTEC DD-X, ILFOTEC HC, MICROPHEN or RT RAPID developers.

For some of the films the wording is clearer so I think it’s just a matter of inconsistent writing. FP4 for example:

FP4 Plus has a speed rating of ISO 125/22º to daylight. The ISO speed rating was measured using ILFORD ID-11 developer at 20ºC/68ºF with intermittent agitation in a spiral tank. Best results are obtained at EI 125/22, but good image quality will also be obtained at meter settings from EI 50/18 to EI 200/24. It should be noted that the exposure index (EI) range recommended for FP4 Plus is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard.

Yes that is pretty clear to me so other than D3200 where it is clear that this is not the ISO speed I wonder where else it is confusing?


pentaxuser

 

[Bill Burk]

The Ilford data sheets use relative log exposure, so there's not really much more they can do than give than an impression of the type of curve of the film. In my opinion, a good Gamma-time curve would be more helpful.

Their graph is crisp and clear, I think it transcribed fairly well. By tentatively pinning LogE at the speed point per corresponding film, I think the underlying exposure can be nearly identified. They were a little goofy changing the relative exposure between Delta 100 and FP4+ so their two graphs don’t make sense until you realize that and re-draw them aligned for exposure.

Here’s transcription of Delta 100 from their data sheet.

 

[Lachlan Young]

Too often film speed is conflated with exposure. Most of the discussions about film speed are really about exposure.

Exactly - more often than not people seem to be testing errors in their metering and/ or displaying a failure to understand that there are good reasons (perceptual and marketing) why shadow speeds between manufacturers might vary a bit, particularly in practical use.

In my opinion, a good Gamma-time curve would be more helpful.

They exist in the data for Deltas 400 and 3200 and used to exist in one form or another for most of the rest of the Ilford range - there will be some very banal reason why they got rid of them.