Developer Film Speed

Discussion in 'Talk About Developing Film' started by Ian-Barber, Jan 6, 2019.

  1. Ian-Barber

    Ian-Barber Admin Staff Member Registered User

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    When people talk about developers and film speed, what are they actually talking about and what are we likely to see in a negative.
     
  2. David M

    David M Well-Known Member Registered User

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    Film speed is a misleading term here. The film remains the same and its speed as such is measured by a precisely defined standard process. This is not quite useless pedantry. We are not going to out-guess Kodak and Ilford.
    What we determine is an Exposure Index, or a Personal Exposure Index.
    Changing developer, developer dilution, developing time or temperature, or agitation, will produce a different negative with more or less highlight density, more or less shadow density or more or less overall contrast. There might be more or less fog and there will be other less obvious differences.
    Generally, we judge the EI on the amount of shadow detail, or rather, printable shadow detail. In most of the fascinating discussions I've followed on negatives and their interesting lives, the print seems to be quite forgotten and the whole purpose pf photography reduced to obtaining specific densities on the neg. No doubt it's great fun.
    So we are talking about getting enough density in the thinnest areas to make a print that satisfies us. As shadow detail must depend on sufficient exposure, we change the setting on our meter to get the desired result in the print. We call that our personal EI. Usually, but not inevitably, it's lower than the number on the box.
    Then we choose a developing time to get the kind of highlights we like when we print. We may select our developer for a number of reasons, like apparent sharpness, finer or coarser grain, ease or speed of use, economy and longevity.
    I'm afraid there's no real substitute for wasting some film and time to establish all this.
    That statement is too sweeping. We could simply learn from experience by changing what we do, every time we do it until things seem to be going well, but this would give us an uncertain foundation to deal with unfamiliar circumstances.

    The difference between a really excellent neg and an adequate one is unlikely to be visible to the naked eye. The only real test is the print.
     
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  3. Alan9940

    Alan9940 Active Member Registered User

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    I think David has explained it pretty well. The box speed is determined by the manufacturer under very specific laboratory conditions. Your personal EI is determined based on sensitometric testing or empirically and is tailored to your personal equipment and workflow. Therefore, film speed is a moving target.
     
  4. Ian-Barber

    Ian-Barber Admin Staff Member Registered User

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    I understand that bit, but the bit I was not getting was when people refer to developers loosing or increasing film speed or have I misread it
     
  5. Stephen Batey

    Stephen Batey Well-Known Member Registered User

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    Very simplistically a fine grain developer may work by solvent action and dissolve away developed specks; this may reduce the overall visible grain, but it will also reduce the amount of silver in the image, giving a less dense negative that needs more exposure to compensate. Hence a loss of "film speed".
     
  6. Ian-Barber

    Ian-Barber Admin Staff Member Registered User

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    Thanks Stephen, that explains it nicely for me.
     
  7. Alan9940

    Alan9940 Active Member Registered User

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    I've always heard of certain developers being "speed increasing" developers, but, personally, I've never measured one that actually increased speed. Significantly expanding/reducing development time can affect film speed, but over my years of testing various films & developers I've never found it significant enough to be concerned with.
     
  8. David M

    David M Well-Known Member Registered User

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    In practice "speed increasing" seems to mean getting enough density in some of the neg to make some sort of print when any kind of image will be better than none. Typically, it generates a rather harsh negative, which gives contrasty prints that some people may like. A skilled printer or scanner may be able to rescue more detail than expected. It seems easier to use a faster film.

    It's possible to express changing negative density in different ways, such as calling it a change in film speed, or calling the same procedures pushing and pulling.
    The fact is that more exposure makes the negative darker and more development makes it darker too. These are the factors that we juggle with.
     
    Last edited: Jan 8, 2019
  9. Alan9940

    Alan9940 Active Member Registered User

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    David, I agree with your comments. My point is that, for example, many years ago when I used Ilford DD-X I had read that it was common to shoot 100 box speed film at EI 160 due to the "speed increasing" nature of this developer. I tested a few of the ISO 100 films I shot at the time and measured the results on a densitometer. My personal film speeds, based on the main film developer I used at the time, didn't vary much at all from the DD-X developed negs. I could have easily contributed the minor differences to other factors such as flare, etc.

    Personally, I think personal EI is a bit of a moving target because variables play into it that are beyond our control; for example, shutter speeds can change over time. How many of us tested our shutters at the time of the original film speed test, then periodically test, again, over xx years? Film emulsions can change slightly over the years, too. Is that Tri-X sheet film I tested 30+ years ago the same as the film I'd buy today? No. We all know that Tri-X sheet film was reformulated slightly years ago. Anyway, just sayin...
     
  10. Ian Grant

    Ian Grant Active Member Registered User

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    Tri-X has been revised and upgraded quite a few since it was first introduced in 1939 as Kodak's high speed competitor to Ilford Hypersensitive Panchromatic. In fact Ilford HP2 had been released just before Tri-X. During the war Tri-X disappeared probably due to non availability of a component which had come from Germany.

    There were variations in Tri-X depending on where it was made and coated, production ceased in Hungary due to the German invasion the Kodak Ltd coating plant was then run under Agfa's control until being nationalised after WWII and becoming Forte. When I first used Tri-X in the late 1960's Kodak developer data-sheets recommended different times and ASA/BS speeds for the US, Canadian, and British, versions of Tri-X. It was the only film with these variations later with a switch to de-activated Gelatin and controlled Sulphurisation the variations disappeared.

    Eastman Kodak began having issues with Gelatin in the US because of isotopes from the atmospheric nuclear tests this lead to new techniques to de-activate the Gelatin, and these days Thiosulphate is used to add the Sulphur spots which is far better controlled compared to relying on natural active Gelatins.

    In practice I noticed no differences between FP3 & FP4 and later FP4+ in terms of EI and development times.

    Ian
     
  11. David M

    David M Well-Known Member Registered User

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    We do seem to be converging on the idea that significant speed increase is largely a myth. Pushing a film in poor conditions might be something that war photographers needed to do. On the whole, it doesn't seem very relevant for LF users, unless there's a train to catch.
    There is always intensification. Although I don't really like returning to the shrine of St AA, he does tell how he eventually intensified the foreground of Moonrise. (40 Photographs, pp 40-43.)
    Another view I've come across is that although some developers may increase the density of shadow detail, they also increase the base fog so that he difference between the image and the background remains much the same. This is mere hearsay on my part.
    Flashing might be a useful resource when caught in the field with a low-light exposure problem.

    Joanna hinted at a technique that she'd evolved...
     
  12. Ian Grant

    Ian Grant Active Member Registered User

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    PQ - and other Phenidone based film developers do give a slight boost in speed compared to the equivalent MQ based formulae, I should add when used alongside a second developing agent , on it's own Phenidone is quite a poor low contrast developing agent compared to Metol. Metol is suppressed by Bromide so on a micro level Phenidone is a far more effective developing agent as it tolerates much higher Bromide levels. In purely weight terms 0.2gms Phenidone is as effective as 2gms Metol and will give an approx 1/2 a stop effective speed increase.

    One disadvantage is some PQ developers give a very slight increase in grain sharpness an example is Microphen/ID-68 which has been balanced to give a slightly higher speed increase. Xtol uses Ascorbate instead of Hydroquinone which along with the Phenidone gives better shadow detail while still producing finer grain than Microphen/ID-68.

    For push processing Microphen/ID-68 or Ilord DD-X give the best results, I used a lot of HP5 pushed in ID-68, however I switched to push processed XP-1 later XP-2 once these films were released as I had finer grain and better contrast and tonality when pushed processed. XP-1 was once available as sheet film - I never used it though.

    Ian
     
  13. David M

    David M Well-Known Member Registered User

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    A very clear exposition, Ian. Thank you.
    For photography on a tripod, half a stop doesn't seem too significant.
    I'd like to find a developer that reduced Foma's spectacular reciprocity failure. Is there any such thing?

    There might be different ideas in peoples' heads when they speak of speed increase. One person might think of needing to get any kind of image at all, despite difficult circumstances, but another might be looking for "...better shadow detail."
    In my mind, the first one is associated with 35mm and the second with LF. Others may have different views, of course.
     
  14. Ian Grant

    Ian Grant Active Member Registered User

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    I did some practical low light testing with Fomapan 200 a few years ago and found that the reciprocity was nowhere near a bad as Foma's data-sheets suggest.

    Here's a post I made on another Forum 11 years ago, I developed in Pyrocat HD and shot the film at 100 EI, I never tested for night shots as I'd use HP5 instead:

    Fomapan practical tests

    Just did some practical tests and the reciprocity with Fomapan 200 was not at all like the published data.

    At 1 second it only only needed around half a stop (recommendation is 1.5 stops) and at lower light levels 10 seconds it was about a stop (not the 3 stops recommended). These test were made in poor daylight 1 second @ f8 100 EI and very low interior lighting 10 seconds @ f8. These are the conditions the film will be used in.

    Still need to test how the film behaves with nigh shots, but it seems to be only a little worse than HP5 / Tri-X for reciprocity failure.

    Ian
     
  15. Ian Grant

    Ian Grant Active Member Registered User

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    I've had a situation where I needed to push process 5x4 HP5 and can foresee doing it again using Pyrocat HD. The first time was successful in terms of the negative quality, tonality/shadow and highlight detail, grain etc, however even at 1600/3200 approx EI I was limited to 1/25th @ f5.5, if Tornado hadn't been an hour late it would have been 400EI and 1/100 @ f16 :D

    The Severn Valley Railway have some night time trains during their Gala weekends and I plan to do some dusk shots which may well require push processing HP5.

    Ian
     

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