Kodak Portra - reciprocity?

Doc W · Dec 3, 2015

I am going to use Portra 160 and 400 (4x5 and 120) to shoot some dark church interiors which will require somewhat longer exposures. I don't mean long in terms of minutes, probably somewhere in the 1 second to 15 second range. Kodak just says to do tests to determine the exposure time but I am a little short on time. Does anyone have any experience with long exposures with Portra?

What about EI? I usually shoot colour negative a third of a stop lower (so 160 at 125 and 400 at 320) but I don't know about these dark and shadowy interiors. Should I open up a little more?

benjiboy · Dec 3, 2015

I suggest you look at the Kodak technical leaflets on these films online, they have all the reciprocity figures

Doc W · Dec 3, 2015

benjiboy said:
I suggest you look at the Kodak technical leaflets on these films online, they have all the reciprocity figures

I must be missing something. I looked at Tech Pub E-4050 and this is what it said:

Adjustments for Long and Short Exposures
No filter correction or exposure compensation is required
for PORTRA 400 Film for exposures from 1⁄10,000 second
to 1 second. For critical applications with longer exposure
times, make tests under your conditions

wildbill · Dec 3, 2015

(there was a url link here which no longer exists)

there are apps to do calculate this if you have a smartphone

Chan Tran · Dec 3, 2015

Doc W said:
I must be missing something. I looked at Tech Pub E-4050 and this is what it said:

Adjustments for Long and Short Exposures
No filter correction or exposure compensation is required
for PORTRA 400 Film for exposures from 1⁄10,000 second
to 1 second. For critical applications with longer exposure
times, make tests under your conditions

That's true because Portra is not for long exposure but Ekta is.

Les Sarile · Dec 3, 2015

Doc W said:
I must be missing something. I looked at Tech Pub E-4050 and this is what it said:

You're not missing anything but it's ok as I have shot practically all the Kodak films for extremely long exposures (> tens of minutes) without issues. The one below is an example of an interior shot on Kodak Portra 400 that at >30seconds.

Although reciprocity won't be a problem, adjusting for lighting temperatures will be.

TheFlyingCamera · Dec 3, 2015

Les Sarile said:
You're not missing anything but it's ok as I have shot practically all the Kodak films for extremely long exposures (> tens of minutes) without issues. The one below is an example of an interior shot on Kodak Portra 400 that at >30seconds.

Although reciprocity won't be a problem, adjusting for lighting temperatures will be.

I've found at least when scanning my Portra (and even my Ektar) that when working with mixed lighting conditions, there is very little correction I need to do for color.

As for long exposures, the general principle with color negative films is: between 1 second and 30 seconds, add one stop. Over 30 seconds, add two. But some films are better and some are worse - when in doubt, Google is your friend. Search on the specific film and "reciprocity characteristics" and you'll get plenty of information. But the 1 for 30, two for more rule works quite well with the Portra family.

David T T · Jan 4, 2016

This is an *unverified* chart for Portra 400/160 I downloaded a couple of years back, but can't seem to find online anymore. Seems to be fairly accurate in my experience.

macfred · Jan 4, 2016

David T T said:
This is an *unverified* chart for Portra 400/160 I downloaded a couple of years back, but can't seem to find online anymore. Seems to be fairly accurate in my experience.

QUOTE]

Here we go ... https://www.flickr.com/groups/477426@N23/discuss/72157635197694957/

Doc W · Jan 4, 2016

All of this is very helpful. Thanks to all.

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