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  1. #1

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    Arista EDU Ultra Film Speed

    Hi all. I have a question regarding the true ISO of the film I use...

    I have read many times that people who shoot with Arista EDU Ultra 100 actually rate it at about ISO 50, and sometimes ISO 32.

    How do I actually treat a 100 speed film as if it were ISO 50? In my mind I have thought about it in the following ways:

    Do I just double my exposure times and develop normally?
    Do I expose regularly and halve the developing time or the developer dilution?
    Do I double the exposure AND change the development time?

    I've also wondered if there are actually multiple correct approaches just like there are multiple combinations of aperture and f/stop for the same light reading...Any info would be much appreciated.

    Thanks much,
    Ryan

  2. #2
    rjbuzzclick's Avatar
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    I generally shoot it at 50 and develop it at the times for 100.
    Reid

    http://www.flickr.com/photos/rjbuzzclick/

    "If I had a nickel for every time I had to replace a camera battery, I'd be able to get the #@%&$ battery cover off!" -Me

  3. #3
    MattKing's Avatar
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    Welcome to APUG.

    I notice that you are a "pinhole" shooter. That tells me that you might be working with very low light levels (at the film plane) and correspondingly long exposure times. If that is the case, most likely you will be dealing with reciprocity failure as well.

    As different films experience reciprocity failure in different ways, you may want to clarify that your question applies to long exposures (if it does) so those who use the film in those conditions can help you.

    If you are working under more typical circumstances (e.g. f/8 @ 1/250 sec), the film won't experience reciprocity failure, so the different aperture and shutter speed combinations that are reciprocals of each other will give you the same results.

    Technically speaking, the ISO of the film is a set amount, determined under specific conditions. Those conditions are very different from the conditions encountered in pinhole work, so it is usually necessary to determine different Exposure Indices (EIs) for metering under those conditions.

    And of course, many people will prefer to use an EI that is different than the ISO of the film when metering under "normal" conditions, because they prefer how the film responds when they meter that way. The post above from rjbuzzclick is an example of that.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  4. #4
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    Many rate film at an exposure index other than than the "official" ISO speed, for different reasons. Some arrive at their preferred EI through testing, and others (like me) just make adjustments until we get results we like. When I was a QC tech at a commercial portrait lab, we told our photographers to rate Kodak Vericolor III (ISO 160) at EI 100 (I don't recall the stated reason). I often rate Tri-X at 200 instead of 400, and develop normally, because it helps me get better shadow detail. When I shot slide film, I sometimes set the ISO 1/3 of a stop faster (say 64 instead of 50) to prevent blown highlights. So yes, there are multiple correct approaches; which are best for you is determined by your own results.

  5. #5

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    @MattKing, thanks, I've been meaning to join this forum for a while now!

    I guess my question is more about how to understand the relationship between developing times, exposure, and the rating that one gives a particular film. I'm getting nice results using the ISO 100 rating, but I'm still interested in understanding more about how I can experiment with rating it differently to see if I can get more out of the film.
    The film I use for my 120 pinhole cameras are the Arista stuff I mentioned above, and Neopan Acros. Both have very "pinhole friendly" reciprocity curves. Especially the Acros. I can shoot exposures well over 30 seconds with no adjustment for r.f.

    I recently switched all of my cameras' exposure charts over to LV instead of EV. That is, instead of changing my light meter to the ISO of the film or paper I am using, I meter everything at ISO 100 and compensate for the film speed after I get the light reading. Are LV and EI the same thing?

    Thanks for the info,

    Ryan

  6. #6
    rjbuzzclick's Avatar
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    From my experience, I would say that Arista EDU's reciprocity failure is much worse than Fuji Acros. According to the data sheets, Acros is good out to two minutes without compensation whereas Arista EDU needs compensation starting at one second. I've had shots using Arista EDU that metered at ten seconds, but with compensation actually needed 80 seconds of exposure.

    My reason for shooting Arista EDU at 50 is for better shadow detail. Like rthomas above, I arrived at this EI by making adjustments in my process until I was happy. I still continue to tweak things a little bit here and there as I go along.
    Reid

    http://www.flickr.com/photos/rjbuzzclick/

    "If I had a nickel for every time I had to replace a camera battery, I'd be able to get the #@%&$ battery cover off!" -Me

  7. #7
    Roger Cole's Avatar
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    ANY film has worse reciprocity failure than Acros which as far as I'm aware has the least of any film, though the advantage of base speed means exposures will still be shorter with TMY-2 out to pretty long ones. OTOH Arista is Foma and it has about the worst (THE worst that I'm aware if) reciprocity failure. It's inexpensive and not bad film but not so good for long exposures.

    These are about the most and least (except for x-ray) expensive black and white sheet films. Most others will be in between on both criteria.

  8. #8
    MattKing's Avatar
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    Quote Originally Posted by rydolan View Post
    @MattKing, thanks, I've been meaning to join this forum for a while now!

    I guess my question is more about how to understand the relationship between developing times, exposure, and the rating that one gives a particular film. I'm getting nice results using the ISO 100 rating, but I'm still interested in understanding more about how I can experiment with rating it differently to see if I can get more out of the film.
    The film I use for my 120 pinhole cameras are the Arista stuff I mentioned above, and Neopan Acros. Both have very "pinhole friendly" reciprocity curves. Especially the Acros. I can shoot exposures well over 30 seconds with no adjustment for r.f.

    I recently switched all of my cameras' exposure charts over to LV instead of EV. That is, instead of changing my light meter to the ISO of the film or paper I am using, I meter everything at ISO 100 and compensate for the film speed after I get the light reading. Are LV and EI the same thing?

    Thanks for the info,

    Ryan
    Ryan:

    I use LV to indicate a light value - a measure of the intensity of the light in the scene. It is film independent.

    EI is a measure of the light sensitivity of the system, including factors like the film, the meter, the camera equipment, your metering technique, your preferences with respect to shadow detail (in the case of negatives) and, to a certain relatively small extent, the developer you are using.

    The ISO is a measure of the light sensitivity of the film when measured under very specific, repeatable circumstances - those circumstances will most likely be at least slightly different then yours. The ISO rating allows you to compare films from different manufacturers.

    When it comes to developing times, within a reasonable range, they have relatively little effect on shadow detail. They have a relatively large effect on contrast.

    In the pinhole world, you are often working at light levels (at the film plane) where reciprocity fails. As a result, it is not uncommon to have the shadows record on the film with much, much less density than the highlights. The difference between the shadow density and the highlight density is much greater then when the light levels all around are much higher (at the film plane). As a result, the overall contrast of the negative may be increased. This may lead you to decrease development time, to tame that contrast. But you may prefer not to make that change.

    If you experiment with different ratings, you are essentially experimenting with different ways of interpreting the information from your meter, in light of the behaviour of your system (including the film). Your goal is to get the right density in various parts of your negatives, but you are concentrating particularly on the shadow densities.

    If you experiment with different development times, you are essentially adjusting the contrast between the densities which record the different parts of the scene, while concentrating particularly on the highlight densities.

    Hope this helps.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  9. #9

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    Quote Originally Posted by MattKing View Post
    As different films experience reciprocity failure in different ways, you may want to clarify that your question applies to long exposures (if it does) so those who use the film in those conditions can help you.
    And Fomapan 100/Arista EDU 100 has *absurdly* terrible reciprocity failure, making it probably a poor choice for pinhole work unless you have bright conditions and/or a long time to wait around for an exposure. I've actually used it quite a bit for long nighttime exposures, developed in Diafine---15 minutes at f/8 was my typical starting point for your average nighttime cityscape, and if you scale that time to pinhole apertures...

    -NT
    Nathan Tenny
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    The lady of the house has to be a pretty swell sort of person to put up with the annoyance of a photographer.
    -The Little Technical Library, _Developing, Printing, And Enlarging_

  10. #10

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    For my pinhole work I keep two films in stock. Fuji Acros and Foampan 100. They have very different “Schwarzschild effect” a term I much prefer to "reciprocity failure". There is no "Failure" it is just a different aspect of the film that can be exploited to great advantage. I use the films differences in this area to get what I need.

    For example I can take photo inside a crowed building and have no people show up in my final photo if I use Foma film with this "Failure".

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