Arista EDU Ultra Film Speed

Discussion in 'B&W: Film, Paper, Chemistry' started by rydolan, Apr 21, 2013.

  1. rydolan

    rydolan Member

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    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. rjbuzzclick

    rjbuzzclick Member

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    I generally shoot it at 50 and develop it at the times for 100.
     
  3. MattKing

    MattKing Subscriber

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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.
     
  4. rthomas

    rthomas Member

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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. rydolan

    rydolan Member

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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. rjbuzzclick

    rjbuzzclick Member

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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.
     
  7. Roger Cole

    Roger Cole Member

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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. MattKing

    MattKing Subscriber

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    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.
     
  9. ntenny

    ntenny Member

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    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
     
  10. brianmquinn

    brianmquinn Member

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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".
     
  11. Roger Cole

    Roger Cole Member

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    You can do the same thing with a small stop (or pinhole) and a neutral density filter. It is a "failure" in the sense that the regular time/intensity rule for equivalent exposure fails to provide equivalent exposure. It also causes a contrast increase because the effect (or failure) is more pronounced in darker areas making them proportionately even darker. And if you reduce development to compensate for the increase in contrast you lose yet more film speed (decreasing development does cause a noticeable loss of speed, it's just that increasing it doesn't actually increase speed, at least not very much.)

    Glad it works for you but I confine my Fomapan exposures to 1/2 second and shorter. Anything longer gets TMY-2.
     
  12. HTF III

    HTF III Member

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    The point of doing pinhole escapes me. Why would.... nevermind. Just because some things CAN be done, why do them? Anything that can be done with a pin hole can be done better with a lens, I'm sure I can fabricate a radio control plane that flies for 20 minutes on rubber bands, but why would I want to? I'm sure I could re-fabricate a light bulb with a grid from a piece of back porch screen and a plate and make an amplifier out of it, but why would I want to?:munch: PS--don't you guys be deterred or offended at my apparent attitude on the subject. It'sall in point-of-view. I'm a guy who spends too much of his life re-inventing the wheel, just for financial viability and sustenance, and survival. A pinhole camera, playing golf, and going to the dentist all hold equal measure on my list of exciting things to do.
     
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  13. NedL

    NedL Subscriber

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    Because it's fun. And amazing. But then I also think a radio controlled plane that could fly for 20 minutes on rubber bands would be cool and a homemade working vacuum tube from a lightbulb and porch screen would be amazing too! Also the "better with a lens" part is very subjective... it won't make a better pinhole photograph! Don't worry not deterred and not offended... slightly bemused that you don't see the value and "wonder factor" of these things.

     
  14. Roger Cole

    Roger Cole Member

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    I'm with the "because it's fun and cool and amazing" crowd - reason enough if you want to. But I'm less sure that anything done with a pinhole can be done with a lens. A pinhole is intrinsically soft focus, varying from quite soft to almost sharp. That alone can be hard enough to do with a lens but the other facet is that the pinhole creates an image with the same degree of sharpness, or unsharpness if you prefer, at all distances. You can stop down a lens, but that just makes it sharper until you reach diffraction problems when it starts getting less sharp again. I know of no way with a lens to render the image uniformly soft focus from inches to infinity. That gives a pinhole image its own aesthetic.

    I'm thinking of trying it with some of the infrared film in my freezer. :smile:
     
  15. Klainmeister

    Klainmeister Member

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    There's a few good reasons:

    1) Expense. Cameras are simple and cheap to build or even purchase. Why the heck not?!
    2) Creativity: the images are unique and provide a visual experience quite different from anything else
    3) simplicity. Point, expose, develop and there you go! This, for me is the #1 reason. Photography is a weird skill because you can make it as simple or complex as you want. In my case, after years of getting into more complex processes and workflows, I wanted to go back to basics. It really makes you focus on subject and composition when you have nothing else to worry about.

    Oh, and it's fun!
     
  16. HTF III

    HTF III Member

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    I have gone through my whole life seeing things "uniformly soft". I have had to wear glasses just to be half blind. I guess it's all in point of view. Carry on, with my blessing. Better a pinhole print than ANYTHING off a digital camera.
     
  17. Roger Cole

    Roger Cole Member

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    I have to wear glasses too, but I'm 20/20 at distance with them (and better than normal up very close without them.) I like sharp for some things, but there's a dreamy quality to some pinhole images that's nice too. YMMV of course. Plus it's fun to make an image so simply, for some folks. :smile: