Personal EI Index

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

  1. Ian-Barber

    Ian-Barber Administrator Staff Member

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    Is it possible to calculate a personal EI index for a given film with an X-Rite ColorMunki or does one need more sophisticated measuring devices
     
  2. Alan9940

    Alan9940 Active Member

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    I'm going with no. For the most scientific approach, you need a densitometer. For the rest of us, it can be done visually or empirically. Following the empirical route, I would simply pick a film, expose to scenes you normally shoot, print, and then analyze shadow areas. If your critical shadow areas are too dark, lower your EI; if too light, raise your EI. Rinse-n-repeat until you get exactly what you want. To ensure you're marching directly toward your goal, make sure all variables are kept the same.
     
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  3. David M

    David M Member

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    I would suggest that this is possible without densitometry. Firstly, please remember that we are not finding a "correct" film speed. We are establishing a figure that relates to our own practice, materials, habits and equipment.

    Everyone's set-up is different and each of us will have a different idea of what constitutes a fine print. We could write a long list of potential variables. The personal EI is a way of summing up all these variables. I think we already understand this.
    The usual procedure is to establish what exposure will give you a Zone One density on the print. The actual density of the negative is largely irrelevant; it's what your system will print as Zone One that counts.

    So, expose the usual Zone series of negs, metered to give a Zone One exposure, at box speed, box speed plus one, two, three., four... stops and develop them in a normal way, following the instructions on the bottle. (We can only deal with development when we have established a personal EI.) It makes sense to include a number or letter in each frame and although a blank surface is usually suggested, a slightly textured surface may yield more information later on.

    When you have the negs, scan each one, all at the same settings, including a portion of exposed surface and the unexposed rebate. You might cut off a the part with the identifying number and scan them together in one scan to eliminate scanner variables.
    Now make prints of each scan or the composite scan. Use the paper that you normally use for your finest prints. The rebates should all print the maximum black that your printer can manage, but no more. That is, it should be as black as the clear space on the scanner bed where there is no negative at all. You will still be able to see the cut edge of the neg.

    One (or more) of them should show no difference in the print between rebate and exposed film but the next one in the series will show a small difference between the maximum printer black and a very dark grey. If you used a textured surface for the test, the next one should show a trace of texture in the exposed part and this will show that you have established where Zone Two lies. This assumes you have tested at one-stop intervals, of course. You prefer to choose a smaller interval.
    Now, you have established a personal setting for your exposure meter that will give you reliable detail in the shadows.

    I think you can see that you could do a development test in much the same way, always remembering that you are looking for what happens on the print, and not on the negative. The negative is the net in which you capture the butterfly, not the butterfly itself.

    Of course, if you change your camera, or film, or paper, or your printer, and you're a picky sort of person, you might have to do it all again.
     
  4. Ian-Barber

    Ian-Barber Administrator Staff Member

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    Thanks @David M for your explanation.

    This is exactly what I have been doing for the past 7 days, testing various papers. From my setup, I am finding that the V800 Epson scanner seems to struggle with a negative which has been exposed with a textured surface +4 stops above the meter reading.

    +3 stops above meter reading appear to yield acceptable results on Baryta paper but +2 above the metered reading for matt is much mored defined in the texture.

    This has me thinking.... does a consumer type scanner hold the same information as grade 2 paper in the sense that when exposing the negative we still need to be working in a 4 stop range.
     
  5. David M

    David M Member

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    You seem to be further down the path than I am. I find that for scanning, I need a much softer neg with generous exposure. Obviously, I can get soft neg by reducing development, but the lesson that I have found is to be more vigilant when metering the lower Zones. It might be heresy, but I like to have a small gap at each end of the histogram. Without any testing to justify it, I've rounded down my EI to compensate for the reduced development.
    I recently had to print some images on a different printer on a different paper and I was surprised that the shadow detail, very obvious on screen, came out as a murky jungle. You seem to be finding that the paper is at least as important as the rest of the process.
    In the good old days, of course, photographers had favourite papers, like Record Rapid, but I've not seen any advice to include the paper in traditional wet Zone testing. It seems to have been assumed that a good negative was a good negative was a good negative.
    We seem to be moving away from that idea and towards the idea of the "printable scan" if that makes any sense.
    Another factor that I've not heard mentioned is fashion. I can recall when a good print was a print with "a good black" and the most admired prints had shadows like black holes. It was called a Punchy Print. This must have had a trickle-down effect on exposure preferences. I seem to recall that pushing film was greatly admired, too.
     
  6. Ian-Barber

    Ian-Barber Administrator Staff Member

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    • What films are you mainly using in 5x4
    • What developer are you mainly using
    • How vigilant are you when metering the lower Zones
     
  7. David M

    David M Member

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    I've been using mainly Foma 100. Excellent film but the reciprocity is horrendous. I might return to FP4. If I could afford it, I might switch to Acros, but the sheet film costs its weight in gold. (– should we now be saying: "worth its weight in Epson ink?)
    I use mainly Ilfotec HC, with an interval of using ID11 until I got fed up with the mixing. I have a bottle of Rodinal sitting on a shelf.
    "Vigilant" might overstate the case. I meant that I wiggle the meter around more than I did, checking which bit of which patch of darkness gives the lowest reading instead of just picking the patch by eye and assuming that I've got it right. The eye adjusts itself, so it's easy to get it wrong.
     
  8. Ian-Barber

    Ian-Barber Administrator Staff Member

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    I also use a fair bit of FomaPan 100 and yes, the reciprocity leaves a lot to be desired.

    I now rate this film at 50 ISO and because this type of film appears to build up contrast very quickly during development, I tend to reduce development by about 20% - 25% in a high contrast scene.

    I am also doing some testing with placing the important textured shadow detail on Zone 4 in accordance with what I am reading in a book by Bruce Barnbarum.
     

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