Personal EI Test For FomaPan 200

Discussion in 'Talk About Techniques' started by Ian-Barber, Feb 19, 2017.

  1. Ian-Barber

    Ian-Barber Administrator Staff Member

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    Let me start by saying that I don't own a dedicated densitometer so my tests may not be classed as 100% but nevertheless, I shall proceed.

    Using a calibrated Stouffer 21 Transmission Step Wedge, I measured the density of each patch using the Densitometer in the VueScan Scanning Software and compared the results to what was written on the Stouffer sleeve.

    To my amazement, the values returned from Vuescan although not exactly the same, were very close indeed. Step 2 on the tablet is 0.20 and Vuescan reports 0.22 and this is true for all remaining steps.

    Armed with this information, I decided to expose a sheet of Fomapan 200 (4 stops) under what the spot meter exposure was.
    I rated this sheet at ISO 100 rather than the box speed of ISO 200.

    I pulled the dark slide 1/2 way out so that one half would be exposed at Zone 1 and the other half would be my Film Base + Fog

    I developed the sheet developed in Xtol for what I have been using as my normal development time (6 minutes @ 20°C)

    According to my sums, I should be getting a reading of the 0.26 on the exposed side of the negative which is 0.1 above Film Base + Fog.

    Readings obtained from Vuescan Densitometer
    The Film Base + Fog measures 0.16
    The exposed side measures 0.22

    To me, this indicates that ISO 100 would be a good value to use for this particular film.
     
  2. David M

    David M Member

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    This is interesting. I have a scanner, I have VueScan (Hurrah for VueScan!) and I have some step wedges, somewhere. I might give it a try, if only for the fun of it.
    Have you checked how this will print? All that "...discernible difference but no detail..." stuff?
     
  3. Alan9940

    Alan9940 Active Member

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    Ian,

    Given internal camera flare and non-directional light bouncing around inside your camera, I doubt that your "unexposed" half of the film would provide true fb+f. Typically, one simply pulls an unexposed sheet of film from a holder or the film box and toss in with the first batch for film speed. I have no idea how any of this would work using a scanner, but when using a densitometer your fb+f negative is used to zero out the unit; then, your various Zone I exposures are read to find one in the 0.10 range (some photographers go as high as 0.15 for Zone I.) Interesting, though...
     
  4. Stephen Batey

    Stephen Batey Well-Known Member

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    I can't quite see why this would be. I've seen photographs (Roger Hicks, Medium and Large Format Photography) where a dark slde was halved to enable two panoramic photos to be made on one sheet of film, without any noticeable light spread.

    Even with a lot of non image forming light bouncing around in the camera, the dark slide should protect the film underneath. The gap that light could seep through is rather narrow.
     
  5. David M

    David M Member

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    I'm with Stephen.
    If we make a few guesses and assumptions, then the open half of the negative is about 63.5mm (let's call it 64) wide and fully exposed to all the light. The covered part is exposed to whatever can get through a narrow slot. Lets assume that it's 1mm wide. Even if this light were evenly spread over the covered surface, it would be 1/64th of the intensity. I think that this would be seven stops less and I can't imagine that seven stops less than a supposed Zone One exposure could be significant.
    If we then take the inverse square law into account, a few millimetres away from the slot, the film will be exposed to what, for all practical purposes, is total darkness.
    We have also neglected the colour of the sheath. Every time photons encounter its black surface, most of them will be absorbed. Even if I'm wrong by several stops, I think the argument still holds.
    All this assumes no freak reflections or faulty light seals. (I've had both.) I've ignored the width as it's constant for both the exposed film and the slot. And I've ignored the fact the most of the image-forming light will be directional, not diffused.

    Might I insert the hoof of my own hobby-horse? Zone One is not a negative density at all. It is a print density, usually described as being observed by the eye as visibly not quite as black as the blackest black possible on that paper, but not showing any detail to the observer's eye. This is the true test that the negative is properly exposed. It is essentially subjective.
     
    Last edited: Feb 22, 2017
    martin henson likes this.
  6. Alan9940

    Alan9940 Active Member

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    David, Stephen,

    You're both probably correct because my 10x8 Deardorff has a black board that fits into the inside of the rear groundglass assembly that allows two 10x4 exposures on a single sheet of film. That said, though, we're talking a single sheet of 5x4 film! For me and my own testing, if I pull a sheet from the box in complete darkness I'm sure it hasn't been exposed to any light.

    This reminds me of something my photo mentor used to say... He said, "Alan, always setup the camera and prepare for a shot, even if you don't think you'll expose the film because if you're ready and something happens you've got the shot. If the camera is still in the bag, you definitely won't get the shot!" Always made sense to me. ;)

    David, I could argue your premise that Zone I is not a negative density speaking in pure sensitometric terms. But, it's the language that Ansel and Fred Archer devised and it's an easy understandable way to describe exposure/tonal values. Works for me...
     
  7. David M

    David M Member

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    Well, yes... Whatever works, works.
    I think you've put your finger on something important. LF forums abound with beginners saying that they are baffled by the Zone System after valiantly plunging into the fine print of densitometry. They often list the all books they have read, rather than the images they have made. A bit of time spent making mistakes might be the most useful introduction to the Zone System. (...might be true of life in general...)
    I've found that it helps start off with the idea that the ZS is, as you say "an easy understandable way to describe [...] tonal values" and not a puzzle to be solved. Then the idea that the Zones are not arbitrary but follow logically from the controls on the camera – aperture and speed – makes sense.
    If a beginner learns that the goal is to produce the kind of print they want, they can absorb as much or as little as suits their needs.
    Many are baffled by film speed. If you explain that they are not out-guessing Kodak or Ilford but finding a pragmatically useful number to set on their exposure meter, they understand. If things like expansion and contraction are related to values in prints, then understanding follows naturally.
    Many excellent photographers, in a quest for greater certainty, or out of natural curiosity, go on to explore numerical methods. There is no reason not to. If it improves the prints and the vision, this is excellent. But any method that works, works. It's quite possible, as history shows, to generate fine work without encountering 0.01 at all. Development by inspection or split-grade printing might be cited as viable alternative routes to a fine print.

    Myself, I suggest that if we are to use the curve to determine a personal EI, we should really be locating the point where the curve reaches a certain slope, rather than a certain density, but I haven't done this and I won't: it is idle speculation on my part. I suppose this might be called minimum exposure for first printable contrast, rather than first printable density.
     
  8. Alan9940

    Alan9940 Active Member

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    David,

    Very well articulated...couldn't have said it better myself!

    My friend and photo mentor (Fred Picker) tried desperately to make the whole Zone System simple and easy to understand. He described simple tests to determine personal EI and Zone VIII print value. In his newsletters, he later refined the film speed test because letters, phone calls, and actual film speed negatives for measuring showed that many folks couldn't follow what he thought to be simple directions as laid out in the "Zone VI Workshop" book. Many folks in the photographic community chastised Fred bemoaning that his methods were "incorrect" and that using the ZS couldn't possibly be that easy! In later years, he described a method he called MPD (Maximum Printable Density) which even further simplified the "Zone System" and is a great technique for roll and 35mm film photographers. To this day, I still employ this technique when shooting MF.

    For myself, I do use a densitometer to determine my personal EI and to obtain proper Zone VIII negative density. But, I'm not a fanatic about it! I did film speed tests over 30 years ago and just recently decided to repeat these tests because I'm using some different films nowadays and because it doesn't hurt to determine if our materials have changed over all these years. (of course they have!) I totally agree with your comment regarding printable contrast, but my reference zone is III because that's where I want to see actual printable texture. Therefore, after I've determined a personal EI and development time for any given film, and start shooting with it, I might adjust my personal EI based on what I see in Zone III in the print. Who knows what the actual negative density is and who cares? If I wind up with 0.18, 0.22, etc, as an actual Zone I negative density, does it matter? Is it "wrong?" Absolutely not!! It's how I want my prints to look and that's all that matters. Not to steal words from Vincent Versace, but he laments that the negative (digital data for him) and all processing techniques leading up to the print are in service to the print! Couldn't agree more...

    Thanks for the stimulating conversation.
     
  9. David M

    David M Member

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    Thank you.
    So far, we haven't mentioned the key word of the Zone System: Visualisation.
    Even if you're not using ZS controls, the idea of examining the scene and deciding what you can do with it is a very valuable one.
     
  10. Alan9940

    Alan9940 Active Member

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    Exactly! Too many photographers new to the ZS get all caught up in the testing, numbers, sensitometry, etc. That's why I liked Fred's methods so well; simply, direct, effective, and once you're done the technical side is out of the way. Then, the photographer is free to concentrate on the hard part of photography; that is, what you put on the film!

    Back when I started using elements of the ZS--nearly 40 years ago now--once I determined my personal EI, film development time, and proper proof time I shot 9 negatives (Zones 1 - 9) and printed 5x4 size prints of each zone. I carried this pack with me into the field for a number of years to help with visualization. It was quite interesting to meter a subject area, place it into a zone, then see exactly the expected tonality of that zone. I learned a lot! But, yes, I totally agree that a most important concept of the ZS is being able to pre-visualize (sort of) your print before you even expose film. I do it so naturally nowadays that it's second nature to me. I couldn't imagine working any other way!
     

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