FP4+ film speed

Discussion in 'Black and White' started by arrthur_nichols, Apr 28, 2003.

  1. Hi,
    I am in the process of determining my personal EI for FP4+ developed
    in X-tol 1:1 for 12:00 at 70 deg F. It seems that I have a real speed
    of ASA 160 based on .10 density for zone I.
    I am using a digital Pentax spot meter that has been modified by Zone
    VI. I also have Seconic spot meter that is giving me as ASA of 80 for
    the same setup.
    I know that everyone has their own speed and that results vary from
    person to person. I am wondering which one of my meters is generally
    more correct. Is there anyone else using FP4 and a Pentax meter that
    could share their film speed.
    When I measure a grey card on a clear day with the Pentax meter I get
    an EV of 14 which puts my exposure one stop over of the sunny 16
    rule. When I use the Seconic I get an EV of 15 which matches the
    sunny 16 rule.
    If I need to get one or the other of the meters calibrated I will.
    I guess that I want to know if ASA 160 for the above combination of
    film and developer is realistc.
    Thanks in advance.
    Art Nichols
     
  2. Sekonic meters are calibrated to 12% reflectance, and many other (but not all) meters are calibrated to 18%. I don't know about the Pentax meter. Most Sekonic meters can be adjusted, and a few have a separate “calibration” adjustment (in addition to an over/under exposure adjustment).

    In any case, even if the meters were calibrated to the same reflectance, they may differ from sample to sample, or differ because of non-linearity, susceptibility to flare, etc.

    The purpose of coming up with your own film speed based on the equipment, film, developer, etc that you are using, is that it adjusts for differences in the meter’s factory calibration (or other errors) since you are calibrating it to .10 Zone I negative density. Therefore, any discussion about which meter is not accurate is meaningless.

    BTW, many people have reported that XTOL 1:1 (or higher dilution) yields increased film speed, so 160 for FP4+ is not out of the question.
     
  3. The film is the ultimate light meter and final arbitrator (sp?) of what's correct. Inspect the negs for shadow detail and adjust your EI on one meter until you're happy. Then, compare readings with the other meter and see what EI setting agrees with the first one. Basically, you have two pieces of measurement equipment (the meters) that disagree, so the same EI setting isn't going to work for both.
     
  4. It is very common to have to set a different speed on two meters. Also two photographers using the exact same particular meter and camera may need to use different speeds because of their metering styles and habits. Whatever works works!
     
  5. lwg

    lwg

    I would bet it is your Pentax that is off. I get an EI of 50-64 with D76 and I think about 80 to 100 with XTOL based on my Pentax Digital Spot (unmodified). This also matches my N80's spot meter. Since it looks like the Pentax is off by a whole stop you could just live with it and remember that fact.
     
  6. Meter calibration issues aside (FWIW, I get as much as one stop differences between my Minolta Autometer IIIF and Pentax Spotmeter V), FP4+ does indeed appear to have a true speed of 125 and possibly higher. The problem has been that I didn't care for the tonality and gradation at the film's nominal speed. Developers tried were Ilfosol-S and ID:11. I don't recall having tried Rodinal on FP4+ yet.

    My favorite results, so far, have been at EI 64 in ID-11, 1:1, 9 minutes. Excellent for outdoor use under bright lighting, scanned or printed using a dichro head.

    I'm also looking forward to trying FP4+ at EI 160 or faster in Diafine just to see the effects on tonality and gradation in contrasty lighting.
     
  7. Yes, remember that the whole point of this meter/film calibration is to find an EI that gives you desired results, using certain meter and certain film. Basically it wouldn't matter if you got a film speed of 800 on one meter and 40 on the other. Just remember it when using the other lightmeter. You could also check if the difference is consistent: 1 stop all over the scale. If it is not, the problem might be bigger. But even then you couldn't know (without testing) which meter shows "incorrect" results.

    This also means that if you hear someone saying that "the true film speed of [FILM] is [EI]" you know that it has no meaning to you and your equipment. The same goes with developing times. It has to be tested.
     
  8. "if you hear someone saying that "the true film speed of [FILM] is [EI]" you know that it has no meaning" Exactly correct. To make maters even worse, some meters are calibrated at 12% and others at 18%. Some people use 35mm TTL auto-exposure metering (in various modes such as matrix, spot, average, etc.), others use external spot meters, and others use incident meters. Most people meter whatever happens to be in the center part of the viewfinder of their auto-exposure cameras, some people meter the shadows, and others meter an 18% gray card, etc. Not only are claims about "true" films speed meaningless, so are claims about pushing film speed also meaningless unless the metering and exposure techniques are explained in detail (and preferably based on some known standard like a gray card or incident reading).
     
  9. "Not only are claims about "true" films speed meaningless, so are claims about pushing film speed also meaningless unless the metering and exposure techniques are explained in detail..."

    Ditto what Mark wrote. I'm big on pushing film when there's no alternative. Heck, sometimes I do it just 'cause I like the look. But I'm trying to eliminate the voodoo and bring more consistency to my technique. I hope to have more specific info to share later this year after doing extensive push processing with various films this summer.
     
  10. You should be able to shoot FP4+ at 120 and dev it in Xtol 1:1 easily with all
    the detail you need with 160 not out of the question. I personally want more
    light on the film so I shoot it at speed and know that I have a safetly margain
    that will still give me a neg. I dev it in Xtol 1:2 more often than not, but have
    used it at 1:3 with great results in 4x5. Xtol is a speed increasing developer
    but some have mentioned in the past that it was not at higher dilutions. Do
    watch agitation. Contrast can increase. If you use both meters on a few
    double shot scenes together your developing will peg which one to use.
     
  11. Thanks to everyone who responded, it seems that the EI that I got with my Pentax meter is not too far off.
    Art
     

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