What does reciprocity failure in color negatives look like?

[MTGseattle]

Well that's anticlimactic . . . but in a good way as that is certainly something I have not encountered.




Thank you for that.

Now I know conclusively I am not encountering any reciprocity failure. In another thread discussing the latitude of Kodak Portra 160 I had provided my latitude testing on some films and one can clearly see the differences in results over and under exposing by a few stops.

This is a test I did using Kodak Ektar 100 . . .

Kodak Ektar 100 latitude by Les DMess, on Flickr


This an aperture priority autoexposure from the Pentax LX lasting about 45 minutes on Kodak Ektar 100 with no compensation . . .

Kodak Ektar 100_31-12 by Les DMess, on Flickr

I am confident that there is no reciprocity failure but just more mix lighting colors . . .

In the long night exposure above (Back of Hoover dam?) I find this to be a pleasing long-exposure color image. Our eyes do not "see" in 45 min increments, so to me, we are in a very subjective area. Is the tone of the concrete correct? Are the various tones correct for the light sources. Is the sky correct? There may well be some scientific way to establish some of these "correct" values, but this is photography. We need to decide what is pleasing to our eye and in my mind, once we stray outside the tables provided by the manufacturer we are on our own.
To put it differently, is a red car the exact same red at night to our eyes? How much manipulation would it take to make it so in a photograph? Nothing I have said helps in the debate regarding the testing, but if any of us are out making exposures that edge into hours, I feel pretty strongly that we can only estimate what will happen on the film without actually doing it.

 

[Alan Edward Klein]

Well, I've always understood it pretty clearly.
Within a certain range of light intensities, reciprocity works perfectly - if you use a series of exposures incorporating variations where the shutter speeds are doubled or halved, accompanied by apertures that are increased or decreased a stop at a time, each reciprocal pair gives negatives of the same density.
Outside that range of light intensities reciprocity fails - the negatives come out less dense, even though the shutter speed and aperture pair remain in the same reciprocal arrangement.
The "misleading" comes from when one tries to put "long exposure" into the term. The "failure" phenomena actually has nothing to do with long exposures - it arises because the light intensity is so low. Discussions about reciprocity failure reference long exposure, because that is the tool we tend to use to try to compensate for the low light levels.
The other type of reciprocity failure - the one that usually occurs only with extremely short exposure times associated with some types of electronic flash - does relate to speed, rather than light intensity

Thanks for making it perfectly clear.

 

[DREW WILEY]

Well, I did learn one new clue since this morning. "CFL's" - one of the very worst forms of lighting for any kind of objective test.

 

[pentaxuser]

Does anyone else have long exposure compensation/adjustment testing results to offer???

I haven't even managed to do any tests on my long exposure to APUG/ Photrio yet

pentaxuser