Methods Of Measuring The Performance Of B&W Developers.

[Keith Tapscott.]

In a thread I started in the UK Regional section of APUG, I asked if anyone knew the particular issue of `PRACTICAL PHOTOGRAPHY` magazine where several B&W film developers were tested.

(there was a url link here which no longer exists)

I was wondering what similar methods are used today, perhaps even by the main film and photo-chemical manufacturers for testing the performance of a B&W film developer?

 

[Photo Engineer]

Keith;

There are two tests involved. One is for film developers and one is for paper developers.

Paper developers were routinely tested for endurance, or the ability to maintain the same results from first to last print in a batch or to last through the day in a tray.

Film developers were tested more for tone scale (latitude), grain and sharpness. This also involves making prints and/or using instrumentation to measure and compare the grain and sharpness numerically as well as visually.

These tests are obvioulsly quite different.

PE

 

[Photo Engineer]

I might add that qualitative tests on films are rather difficult as often sharpness and contrast can be confused by the viewer, and while not a bad thing to have happen, may result in problems over a large number of scenes or films.

PE

 

[Keith Tapscott.]

I might add that qualitative tests on films are rather difficult as often sharpness and contrast can be confused by the viewer, and while not a bad thing to have happen, may result in problems over a large number of scenes or films.

PE

I would have thought that such a test would have been conducted in controlled or constant lighting condition. In the Practical Photography magazine test, a 35mm camera was used with what ever focal length of lens they chose. (I can`t remember). The subject I think was a Church or Cathedral in Peterborough.
A section of each negative/developer combination showed the clock face which represented a magnification of around 36-40X, although my memory of the test is a little sketchy as I think the issue was published around the early 1990s which I no longer have.

 

[Photo Engineer]

Keith;

A low contrast sharp film and a high contrast low sharpness film shot identically and processed in the same developer can give the same subjective result in prints. The difference may only be revealed in quantitative data.

OTOH, the same film in two developers may give different edge effects and thus different apparent sharpness. Or the film may give two contrasts with the same subjective difference in apparent sharpness. In these cases again the quantitative analysiis is a reliable means of determining the effects.

I've also pointed out the importance of micro vs macro contrast when looking at sharpness data. I have posted the graph of this from the seminal article by Kriss here on APUG. That describes how the magnification of the image affects sharpness, and how contrast increases as the edges in the film orignal become smaller.

Testing film developers or films themselves in one developer is a demanding process. Much more so than testing paper developers from the standpoint of image strucure.

PE

 

[Keith Tapscott.]

Testing film developers or films themselves in one developer is a demanding process. Much more so than testing paper developers from the standpoint of image strucure.

PE

In this particular test, several rolls of Ilford FP4 were exposed and developed in a variety of different popular B&W film developers. I assume this film was chosen because of it`s popularity as a general use film in the UK. This was used as a "Yard-Stick" to compare the yield of these developers in terms of granularity and speed, although the differences were quite subtle with most of the standard developers. As I recall, Agfa Rodinal produced the coarsest grain and Ilford Perceptol produced the finest grain.
I don`t recall seeing a similar test published in recent years, probably because of the time and expense involved.
I haven`t seen a test such as this since.

 

[Photo Engineer]

Did they test sharpness in any way?

PE

 

[Keith Tapscott.]

Did they test sharpness in any way?

PE

I don`t think so, although they did include Paterson Acutol and Tetenal Neofin Blue which are designed to increase acutance. The Neofin developer also yielded quite coarse grain which might have been due to the odd agitating method that Tetenal recommended of an inversion of the processing tank every 3 seconds. As I have said, my memory of the test is sketchy and I wish someone would respond to this thread who has also read this magazine issue and perhaps still has this copy in their possesion, as I would like to see if I can order a back issue.

 

[Photo Engineer]

Keith;

Edmund Scientific has some charts that are rather pricey but do the job if one wishes to test resolution / sharpness. I have a negative and positive set to use in testing developers when I get around to it.

I have a set in 4x5 as well that I use for testing prints for sharpness. I have posted some of those results here.

PE

 

[Alan Johnson]

I have the torn out pages of this test showing the clock,but unfortunately they dont have a date on them. The film used was FP4,exposed in a Nikon with a Tamron 90mm lens at f11, processed using times suggested for normal contrast,G 0.55.Published shots show a 36x magnification of the negs taken from photomicrographs of the negs on Fuji 64 Tungsten film.Results for 20 developers were shown,no staining developers though.
The author evaluated the grain,which is pretty clear from the published shots,and also the sharpness which is not really clear.
I'm not sure some of his conclusions would pass APUG scrutiny, eg Perceptol got top marks for sharpness and Ilfosol S top marks for grain,but such a test is still something it would be interesting to see more of.

 

[Photo Engineer]

I am trying to ramp up to do this, as I have to test my own film emulsions for these characteristics. If I can get anything postable I will. My present schedule for this puts such a test and possible post in early 2008 though.

PE

 

[Roger Hicks]

In a thread I started in the UK Regional section of APUG, I asked if anyone knew the particular issue of `PRACTICAL PHOTOGRAPHY` magazine where several B&W film developers were tested...

Dear Keith,

I'm always VERY suspicious of these tests because they do not (cannot) measure tonality. Grain and resolution are reasonably easy to compare, but ultimately for me it comes down to whether I like the tonality or not. Thus I much prefer Foma 200 to Fuji Acros, even though the Acros is far finer grained and sharper.

Cheers,

Roger

 

[Photo Engineer]

And there Roger has hit a major key point in this.

Subjectivity is important in determining what people like.

PE

 

[Keith Tapscott.]

I have the torn out pages of this test showing the clock,but unfortunately they dont have a date on them. The film used was FP4,exposed in a Nikon with a Tamron 90mm lens at f11, processed using times suggested for normal contrast,G 0.55.Published shots show a 36x magnification of the negs taken from photomicrographs of the negs on Fuji 64 Tungsten film.Results for 20 developers were shown,no staining developers though.
The author evaluated the grain,which is pretty clear from the published shots,and also the sharpness which is not really clear.
I'm not sure some of his conclusions would pass APUG scrutiny, eg Perceptol got top marks for sharpness and Ilfosol S top marks for grain,but such a test is still something it would be interesting to see more of.

Hello Alan,
Thanks for that, a pity about the date though as that seems to be the very test that I trying to recall.

 

[Keith Tapscott.]

Dear Keith,

I'm always VERY suspicious of these tests because they do not (cannot) measure tonality. Grain and resolution are reasonably easy to compare, but ultimately for me it comes down to whether I like the tonality or not. Thus I much prefer Foma 200 to Fuji Acros, even though the Acros is far finer grained and sharper.

Cheers,

Roger

Roger, I agree that film choices are very personal and each individual will have their own favourites concerning the choice film and developer combinations. I acknowledge that tonality is difficult if not impossible to quantify. However, I am interested in how the performance of film developers are tested and measured.

 

[Keith Tapscott.]

..............but such a test is still something I would be interesting to see more of.

I agree, although such a test can not measure tonality as Roger has pointed out. It can however, help to evaluate granularity, sharpness and resolution although the perceived sharpness has more to do with edge effects rather than resolution.