How do you expose color neg film?

[chris jordan]

Hey guys. Since switching to color neg 8x10 film (Portra 160 NC) I've been exposing it pretty much the same as I exposed Provia-- rate it at 100, meter for a midtone and let the shadows and highlights fall where they may. But I've noticed that my neg's are coming out a little on the thin side, and I've heard that more dense negs may be better. How do you guys expose color negs for normal C-41 processing?

~cj

www.chrisjordan.com

[Steve Baggett]

I meter as if I were doing black and white (with careful attention to zone III) and then overexpose by 1/2 to 2/3 of a stop. Don't overexpose too much, though.

[Henry Ambrose]

I use mostly NPS and rate it at 100. When in doubt I bracket and give it another stop, especially if its a longer exposure. Once I get past 30 seconds I bracket one and then two stops additional.

[neil poulsen]

I use a spot meter, lower my ASA about a half stop for Kodak, check both the highlights and shadows, and if need be, error to preserve the highlights. I find that Kodak tends to report accurate ASA's, so by lowering the ASA a half-stop, I'm giving a little advantage to the shadows. I try to keep my highlights no greater than about VII.5.

I seem to do OK with the above. But I've been wondering if it might be a good idea to do a quick Polaroid check (Type 664) with color negatives like with transparencies. Metering for color can be a bit tricky. Negative film is proclaimed as having a wide latitude, but perhaps not so wide if one wants optimum results.

I try to keep my color film exposures in the range in which reciprocity holds. If checking with Polaroids, I take reciprocity failure into consideration with a table that gives aperture corrections for each shutter speed.

There is a test possible to check the film's ASA for the given lab, one's meter, camera, etc. Film makers publish a range for an 18% gray target. Meter the target, expose, develop, and have the lab read the target on the film with a color densitometer. I prefer that the results fall between the middle to high end of the published range.

[Bruce Watson]

When I've done 160 Portra NC, I've used the Zone system just like I would for B&W except I tend to contract it a little because Tri-X can handle greater dynamic range than 160 Portra. That is, where I would put shadows that I wanted to carry detail on III for Tri-X, I put them about III 1/2 for Portra. Similarly, I put hightlights on about VII 1/2, instead of VIII.

All rated at 160, which works well with my local prolab's processing.

[Mike Chini]

Depends upon the film. But in general, I expose a bit lower than the standard ISO (ie 320 for 400 speed film) and then process the film +1/2. So my negs are usually rich and contrasty. If the scene is a high contrast scene however, I'll just process the film normally. I find that shooting 400 speed at 200 doesn't give me as much 'punch'. I usually shoot Portra NC films.

[tim atherton]

Here's some other answers...

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=0033DC

[Karl Amo]

Here's yet another approach:

Meter off the darkest object from which you want to capture some detail, and then reduce exposure by 1 1/2 stops.

[Michael S. Briggs]

Your procedure of metering for the midtones and letting the shadows and highlights do what they will do makes sense for reversal film. Reversal film has narrow lattitude so it makes sense to place the important tones where they will reproduce well and accept that less important tones may fall off either end of the characteristic curve of the film.





In contrast, negative film has great lattitude for overexposure, so I would give greater emphasis to metering and placing the shadow tones. If in doubt, give additional exposure.





The characteristic curves published by the manufacturers are informative. For Portra 160 NC, this is Kodak publication E-190 or in pdf form. Past the toe of the film, the graph shows an approximately straight line response for an exposure range of 3 decades (10 stops)! Kodak's graph ends before a real shoulder appears. In comparison, the curve for Provia 100f show an exposure range between shoulder and toe of about 1.5 decades (5 stops).

[Ed Eubanks]

My experience (shooting Portra 160VC in 4x5) has been that Polaroid 690 pack film renders essentially the same tonal range, contrast, and overall exposure as the Portra 160VC, so I typically meter and set my camera, shoot a polaroid to check exposure, and then expose the sheet film. This is in a studio context, where I have the time and freedom to set and re-set everything as much as I want... if you are shooting landscapes/cityscapes, this method may slow you down too much. However, you still might try it in a more controlled setting, just to get to know the characteristics of the film.By the way, this also presupposes that you're using a 405 pack film Polaroid back. I know that this back isn't the preferred choice of most on this forum, so maybe they will chime in and suggest an equivalent to the 690 pack film.