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Thread: Print film - 100 or 160 iso?

  1. #1
    tim atherton's Avatar
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    Print film - 100 or 160 iso?

    I don't use print film very often - and then for either copy work or some interi ors. What is the consenus (and rational) for rating VPS, NPS, Portra etc. Nomina l speed 160iso, but many seem to rate it at 100?

    I am going to be using it for some building/landscape type shots - which I norma lly use E6 films for, but I want a different feel this time.

    Thanks

    Tim A
    You'd be amazed how small the demand is for pictures of trees... - Fred Astaire to Audrey Hepburn

    www.photo-muse.blogspot.com blog

  2. #2

    Join Date
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    Print film - 100 or 160 iso?

    I think the rationale is simply to get full detail by giving a little more exposure than necessary. Remember with print film it is better to err on the side of overexposure than underexposure. 2/3 stop can be the difference between having and not having detail in the shadows.

  3. #3

    Print film - 100 or 160 iso?

    The characteristic curves of the 3 colour layers don't follow too closely in the toe region, so it's better to get any important detail up onto the straight bit of the curve to get accurate colour, and this means giving more than the recommended exposure. Kodak's Portra seems better in this respect. You've got nearly 10 stops of "straight line" to play with anyway!

  4. #4

    Print film - 100 or 160 iso?

    I shoot weddings with medium format cameras and use 400 speed colour neg films at ei 250. My feeling is that you can't hurt colour neg fim by overexposing it by 2/3 of a stop but you sure can by underexposing it. I also don't trust the manufacturers. VPS was ISO 160 right up until Portra arrived. Then Kodak said, well VPS was ISO 100 all along. So why should we belive them now?

    I guess the bottom line solution is to shoot two sheets, one at 100 and one at 160, and decide which on you like best.

  5. #5

    Join Date
    Oct 1999
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    Print film - 100 or 160 iso?

    I have been shooting Portra 160 for weddings for about 1 year. I have been rating it at 160 with excellent results. the film is remarkably consistent. I rate their 400 film 2/3 down though.

    dave.

  6. #6

    Join Date
    Feb 1998
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    Print film - 100 or 160 iso?

    Kodaks book 'The Portrait' rates VPS as 160 in sunlight, 125 with electronic strobe and 80 (with warming filter) in overcast conditions. I have had very good results using these guidelines. Keep in mind that EI rating of your film is only part of the equasion. What you meter for is the other part. With print film, you should meter for the shadows. With reversal film you should meter for the highlights. Metering for the shadows means giving more exposure, so by underating the ISO allows you to meter in a conventional manner, and still be 'metering for the shadows'.

  7. #7

    Print film - 100 or 160 iso?

    This is the first time I've ever participated in a forum, and I don't particularly know why I am doing so now, but perhaps my experience can help. Perhaps not.

    If you use different films a lot, you'll find that the complexity and flexibility of today's pro equipment (considering the ways you can bias both the camera's program for speed or aperture preference, and the film's ISO for metering) makes achieving a level of consistency with values important. The system I have evolved into takes three factors into account and uses a set method to address them. It's not a system anyone knows about or has named, that I've ever seen, but you'll find that after learning the presets (FT and EL compensation - see below) it does reduce the variables for any shot down to one: the subject/zone reference value (SZ).

    The first preset is film type (FT), using the ISO setting to adjust for the type of film, and leaving it there for that film, regardless of other conditions. An auto camera designed to use this system would have a 3-position switch: one setting for reversal film (-1/3), one for natural-color negative films (+1/3) and one for vivid- or enhanced-color negative films and B&W (+2/3).

    The second preset is the environmental lighting (EL), not to be confused with the subject lighting. EL is another way of saying contrast range, but contrast range is difficult to define without math, and that slows down the determination, so it's quicker to think of the overall light, or shadow of the environment which surrounds the subject. I use compensation setting to take care of EL, because the amount of compensation will change under different environmental conditions more often and I like to keep the IE constant for film type. An example: adding +1/3 compensation for shooting in overcast conditions vs. +2/3 in light strong enough to create darker shadows (including flash).

    Finally, I figure and add- or subtract-in the subject-zone (SZ) compensation, which in a sunny, winter, full-body shot could be another +1.

    So, if the film is Portra 400 NC, the FTIE is already +adjusted to 320 (+1/3) and the EL to +2/3 (darker shadows) on the compensation control, the total compensation for this example is +2. If the film is Portra XXX VC, the IE adjust is +2/3, and the example would shoot at +2-1/3 total. If it were overcast, the +2/3 environmental compensation is dropped 1/3 and if reversal film is used, the FTIE is -1/3 instead of +1/3 for NC, and so on. If I move in for a head and shoulders, nothing changes except the +1 SZ value, which will drop to +1/3, and to zero if I go closer for a full face.

    This system provides me with two constants: the film type preset (the FT-IE adjust), and the lighting environment preset (a constant compensation component for sun, shade, strobe, tungsten or filter factor), leaving me to concentrate on the only shot-to-shot variable: the subject/zone reference value, which is dialed into the compensation formula at the brink of shutter release.

    If I were to give it a name, now that I'm thinking of it, I guess I'd call it the FT-EL Preset (already sounds like Nikon, the only 35SLR make I've ever owned; so, it must be good). Works for me, and films today are so widely sensitive that the FT-EL Preset will never leave you with an unusable image. Factor in an old standard to this, the "Sunny 16" rule, and you don't need your meter either.

    ? Malcolm Kantzler. August 28, 2001

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