APX400 + Agfatronics 643 CS=OOPS; POTA developer to salvage?

Discussion in 'Film and Processing' started by murrayatuptown, Oct 14, 2018.

  1. Hello:

    I did an experiment a couple weeks ago with a camera and flash I had never used before...some rationalization and some mistakes leave me with a developing decision to make to possibly salvage the exposures.

    I just got a Bronica ETR with the AE eyelevel finder. I had an Agfatronic 643CS flash I've never used...relatively large; IIRC GN 212 @ ISO 100.

    I shot a roll of APX 400 at a wedding reception as an experiment after the paid photographer left...not my job.

    I put the camera on autoexposure and told myself the flash had a thyristor...but I had it on full power. I used the built-in diffuser, but someone squawked about how bright the flash was.

    I rarely use a flash so I didn't know what I was doing.

    I haven't developed the film yet and it's been on my mind that I may have overdone the lighting...a bit.

    So I am contemplating what I can do to rescue the roll.

    Maybe POTA is a bit extreme, but that's what I'm thinking ...I have the chemicals.

    That or diluted stand development.

    Any advice?

    Thank you

    Murray
     
  2. How far from the subject were you, and how far should you have been?

    From: https://www.foto-r3.com/files/foto_R3_agfaphoto_datasheet_professional_films_en.pdf

    it looks like APX 400 has lower gamma (contrast), and the expected more exposure latitude,
    than is usual for black and white films. Normal might be only two stops.

    You might get dark, hard to print, negatives, but I suspect you will get fine results with
    normal processing.

    Looking at the data sheet again, the development times given are for gamma of 0.65,
    which should be plenty low enough, but there are times for 0.55.

    But OK, with an ISO 100 GN of 212, it would be 424 at ISO 400.

    If I guess 10 to 20 feet, that would be f/40 to f/20.

    Most thyristor flashes that I know of, have more than one choice for auto mode.
    (For the 283, there is yellow, red, blue, and purple.) You could be three or four
    stops overexposed. But maybe you know the distance and aperture better than
    my guess.
     
  3. Probably only 6-15 feet. I started at maybe f/4, then decided to stop down to f/11-16 and rely on DOF as I couldn't see well enough to use the split + Fresnel screen. The room lighting was EV 4-5 (phone light meter)., so I didn't even try any with the flash off.

    Thank you
     
  4. The Agfatronic 643 has a claimed GN of 64 (yeah, right!) in metres/100 ISO. Now makers' guide numbers are always inflated by at least one stop, so that's a real (maybe) GN of 45 @ 100 ISO - 90 @ 400 ISO.

    Assuming that's correct; a subject distance of 3m (10 ft) gets you an aperture of ~ f/32. So you've overexposed by 2 to 3 stops. Not allowing for the diffuser, which will probably knock another stop off.

    At best, I estimate you've overexposed by 1 stop, and at worst by 3 stops. That's if the flash was fully-working and up to spec.

    So, yes a compensating developer is probably called for.

    If you have a flashmeter or digital camera, then it's worthwhile finding the true guide number of that old flash before you proceed. I'm pretty sure you'll find it far less powerful than claimed, and you'll have a much better idea of the amount of overexposure you're dealing with - if any!
     
  5. Also important is what you expect from the scenes.

    As noted, you have a lot of exposure latitude.

    Overexposing, you have a good chance of properly exposing the background, which might be
    significantly farther away. (It happens a lot to me.)

    From the graphs, it looks like with gamma=0.65, it has 14 zones available, compared to
    the more usual 10 zones.
     
  6. - Can't we just use 'stops', not 'zones'?

    Stops define an accurate doubling or halving of light or exposure. Whereas zones...... Hmmm, there are supposedly 3 zones between 18% reflectivity and (by Adams' definitions) 100% Lambertian reflectivity - fresh snow, whitewashed objects, etc. Now if each zone = 1 stop, that takes zone VIII up to a ridiculous 144% reflectivity.

    Something wrong with Mr. Adams' maths or zone descriptions somewhere. So let's just use 'stops' and know exactly where we stand, shall we?
     
  7. I am not big on the zone system, but it isn't so obvious that it makes sense otherwise.

    Exposure latitude has stops, which is how much more the film has than the usual scene.

    But if I say a film has 14 stops, what does that mean?

    I suppose dynamic range, in audio the (log) difference between the quietest and loudest sound,
    expressed in dB, so in photography it could be expressed in stops.

    I could just say the film has 40dB of dynamic range, which would make sense to audio people.
    The mostly straight part of the characteristic curve goes for four decades, which I called 14 zones.

    More usual films are three decades, or 10 zones. It still sounds funny to call it stops,
    but maybe it isn't so bad.

    I wouldn't say increase (or decrease) the exposure by two zones, always stops.
     
  8. I find zones a strange way to refer to a straightforward log lux-seconds scale on an H&D graph to be honest.

    From Adams' books on the subject, it's obvious he equated his zones (exactly) with one stop increments/decrements of exposure or luminosity. However, the written descriptions of the zones just don't tally correctly with that. And I can't understand why he went nearly a lifetime without realising it. Nor any of his obviously very technically competent assistants noticing either!

    The king's not wearing any clothes.
     
  9. I suppose "stops of dynamic range" works about as well.

    But you can't just say "this film has 14 stops", they way I believe you could say "14 zones".

    Audio does everything in dB, but then it is easy with 3dB being a factor of 2 in power,
    or close enough anyway, to convert when needed.

    While a 42dB S/N ratio in audio isn't all that good, I suspect you would not be satisfied
    if I used a 42dB S/N ratio to describe a film.

    But yes, I know how to use an 18% gray card, but don't normally say that I use
    the zone system. Even not using it, though, it does seem a fine way to
    describe the dynamic range of a scene or film. (or digital sensor system.)
     
  10. - We'll have to disagree on that then.
    The phrase "this film has 14 zones" is just as meaningless as substituting 'stops' without the word range added.

    Plus there's a direct relationship between stops and dynamic range in digital bits - in linear space. And you don't have to wear out the shift key denoting stops in pretentious Roman numerals!:cool:
     
  11. Stand Developing is worth considering but your results would interesting yet not 'conventional'. You did say this was an experiment, right?
     
  12. Looking at some of the two-bath recipes...don't have any Metol or HQ, so I found LOMAD developer, which is apparently a clone of Diafine...has ingredients I already have,

    I noticed the similarity to other logarithmic relationships, too, but never thought of using dB there...I feel like I'd have to insist on measuring optical power to use decibels.

    imsphotos: part experimental, part salvage. Not really afraid of being embarrassed by a totally washed out roll, but realizing by no-brainer mistake, rescuing images would be a reward of sorts...I might not have learned about two-bath development otherwise.

    Speaking of pretentious Roman numerals...the Heathkit company made several clock kits, the most abominable being a wooden mantel clock with dot matrix LED Roman numerals, using individual (5 mm?) LED's. It used some quirky logic to avoid too-wide-for-number-of-LED's numeral combinations like IIX instead of VIII...correct but 'unconventional'. Even if you were comfortable reading Roman numerals rendered in primitive dot matrix, the bright red LED's clashed with the traditional wooden clock case.
     
  13. So, how did the 'overexposed' negs turn out Murray?

    Was that flash anywhere near as powerful as its maker's claim?

    I'm willing to bet not.
     

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