Developing Process

Discussion in 'Talk About Developing Film' started by Ian-Barber, Oct 14, 2016.

  1. Ian-Barber

    Ian-Barber Administrator Staff Member

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    Scenario: Total developing time is 10 minutes (normal development not stand)
    1. Roughly, how long through the developing time will the low values (shadow) areas have been fully developed
    2. Roughly, how long through the developing time will the mid values (mid-tones) areas have been fully developed
    I am just trying to build up a mental picture of whats happening as I develop my sheet film in a daylight tank
     
  2. alexmuir

    alexmuir Member

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    I'm not sure that you could put actual times on each step. What I understand is that shadow areas will be developed quickly, and extending development beyond that point will have little effect. Highlight values, on the other hand, will continue to develop, and increase in density, way beyond the time needed for satisfactory shadow development. It is this aspect of the process that allows control of contrast. Short development means low contrast, long development higher contrast. When you do film testing, it is normal to do an EI test first to establish the minimum level of exposure needed to produce adequate detail in the shadow values. You then do a development test to find the minimum time needed to give satisfactory highlight values. I suppose that, once you had your EI established, you could develop at various times short of the standard development time to see when the shadows become less than satisfactory. The same could be done for other values in the mid and higher areas. This would mean quite a lot of testing, but the more data you collect would add to your knowledge of how the film responds to changes in development. Most people who engage in testing, however, seem to find the traditional approach to be adequate, with calculations made for N, N+ and N- development times.
    The characteristic curves published by film manufacturers can also give you useful information about how a film reacts to exposure and development, but I'm not an expert on interpreting their data!
    Do you have an idea in mind that would benefit from precise timings of development for different negative tones?
    Alex


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  3. Ian-Barber

    Ian-Barber Administrator Staff Member

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    I don't have a specific idea but my reason for asking is probably two fold.
    1. I just want to get a better understanding on what is happening to the film after we have added developer and start the agitation process.

    2. As my workflow consists on scanning everything and then inkjet printing, I want the relevant knowledge to be able to produce a negative with sufficient information from one end of the tonal scale to the other in order to get the most out of the scanners capability.
     
  4. alexmuir

    alexmuir Member

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    It's a good idea to have as much information as possible about a particular film and developer combination. Some years ago, I did the EI and development tests for Delta 400 film (sadly not available for LF). I got all the necessary results, and could produce negatives with predictable quality. I then lost interest for a few years. More recently, I bought a small transmission densitometer and got back into testing. I haven't gone the full route of development tests, but found that by making educated guesses at the reduction required from the manufactures standard development time, together with the densitometer readings, I could arrive at satisfactory settings. I use the densitometer readings in conjunction with the method given in the Kodak Workshop publication about advanced B&W photography. It gives you target readings for shadow and highlight values.
    For what it's worth, I've found that the EI for many films is less than the quoted film speed. I have also found that a reduced development (from manufacturers time) is generally needed to get the correct highlight density. What you should arrive at is a negative with good shadow density so as to retain printable detail, and with highlights that are not so dense that they need extensive burning in. This is basically the old advice to 'expose for the shadows, and develop for the highlights'. The densitometer is not strictly necessary, but I like to have something a bit more reliable than my eyes for assessing negatives. I bought mine, a Tobias TQ portable model for about £20 on eBay. It seems to work fine, and came with the necessary calibration patches. If you decided you wanted one, things to check are 1. The calibration test card is included, 2. It has a power supply lead and 3. The lamp is working. There are quite a few offered on eBay, etc, but they don't always look to be complete and working.
    Alex


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  5. Stephen Batey

    Stephen Batey Well-Known Member

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    If you can, I'd recommend consulting Michael Langford's Basic Photography, 3rd edition. There's a very informative (and highly relevant) plate between pages 256 and 257 which has a graph and sample negatives of the same subject, same exposure and 3, 10 and 15 minutes of development. It's the best of its kind I've seen. I stipulate the edition, because it was cut from later ones at some point. I don't have the 4th edition, but it disappeared if not in that then probably the 5th.
     
  6. Stephen Batey

    Stephen Batey Well-Known Member

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    On the more general question of what's going on inside the tank (or emulsion) take a look at Jacobson and Jacobson Developing. I suspect it's long out of print (it was when I last tried to buy a copy) but I did find a pdf download somewhere for the 18th edition (1973). You probably want the chapter on The Progress of Development.
     
  7. Ian-Barber

    Ian-Barber Administrator Staff Member

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    Thanks Stephen, I will endeavour to try and track these publications down
     

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