Print film - 100 or 160 iso?

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I don't use print film very often - and then for either copy work or some interiors. What is the consenus (and rational) for rating VPS, NPS, Portra etc. Nominal 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 normally use E6 films for, but I want a different feel this time.

Thanks

Tim A

-- Tim Atherton (tim@KairosPhoto.com), June 20, 2000

Answers

I think it matters more how you meter the film. I rate the NPS at 160, which is what Fuji says it should be. Others rate it at 100. I get comments from the print lab on the consistency and good exposure on the negatives I give them. I don't know that it matters that much other than using a method that gives you good results with the labs you use and the subject mater you photograph.

-- Dan Smith (shooter@brigham.net), June 20, 2000.

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.

-- Chad Jarvis (cjarvis@nas.edu), June 20, 2000.

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!

-- Pete Andrews (p.l.andrews@bham.ac.uk), June 20, 2000.

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.

-- David Grandy (dgrandy@accesscable.net), June 20, 2000.


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.

-- Dave Anton (daveanton@home.com), June 20, 2000.



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'.

-- Ron Shaw (shaw9@llnl.gov), June 20, 2000.

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

-- Malcolm Kantzler (photography@silkscape.com), August 28, 2001.


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