Reciprocity Failure
May 7, 2015 12:32:30 #
MCHUGH
Loc: Jacksonville, Texas
Is there such a thing as Reciprocity Failure in digital photography like there is in film photography. I know what causes this in film but was wandering if light sensors have trouble absorbing light like the silver in film. I have not experimented yet to check it out. I don't think it exist, but I am not as smart as many on this forum are.
May 7, 2015 12:41:40 #
MCHUGH wrote:
Is there such a thing as Reciprocity Failure in digital photography like there is in film photography. I know what causes this in film but was wandering if light sensors have trouble absorbing light like the silver in film. I have not experimented yet to check it out. I don't think it exist, but I am not as smart as many on this forum are.
Reciprocity failure is a result of chemical processes.
Digital cameras don't have that problem.
May 7, 2015 15:29:11 #
MCHUGH wrote:
Is there such a thing as Reciprocity Failure in digital photography like there is in film photography. I know what causes this in film but was wandering if light sensors have trouble absorbing light like the silver in film. I have not experimented yet to check it out. I don't think it exist, but I am not as smart as many on this forum are.
The short answer is no - the physics is different. But digital sensors also have a low light problem called signal to noise ratio. At very low light levels, you will not get a good image even with very long times because of thermal noise. That's why some astronomy applications use super cooled sensors.
May 7, 2015 16:12:08 #
MCHUGH wrote:
Is there such a thing as Reciprocity Failure in digital photography like there is in film photography. I know what causes this in film but was wandering if light sensors have trouble absorbing light like the silver in film. I have not experimented yet to check it out. I don't think it exist, but I am not as smart as many on this forum are.
M, as has been said, I am not aware of it in a sensor situation.
In film there was the double whammy that both the film and the paper chemicals where optimized to be excited and react to the light for certain periods of time. Not enough and the chemicals didn't properly activate and too much time and again they don't just keep exposing in a linear fashion.
Whether heat build-up can be included in reciprocity I don't know. Cameras do have a built in safety to shut down the sensor if they overheat. Is it related? That needs to be answered by those much smarter than myself!! ;-)
SS
May 7, 2015 16:26:58 #
MCHUGH wrote:
Is there such a thing as Reciprocity Failure in digital photography like there is in film photography. I am not as smart as many on this forum are.
I am not one of the smart ones here, but I read a brief article about this a few months ago. It's not an issue. Just be aware of increasing noise as ISO rises.
May 7, 2015 17:59:33 #
These answers are one of the things which attracted me to this cabal of curmudgeons. They are good! Thank you!
May 7, 2015 19:59:18 #
I had to google that, because I had never heard of it before. If I had heard "nonlinearity" or "low light dropout" I would have understood. So that's what that weird patch of complete darkness in the photo is.
May 8, 2015 11:35:42 #
Math78 wrote:
The short answer is no - the physics is different. But digital sensors also have a low light problem called signal to noise ratio. At very low light levels, you will not get a good image even with very long times because of thermal noise. That's why some astronomy applications use super cooled sensors.
Dave,
There is a little more to the answer of SNR in digital sensors. Digital sensors do suffer from low light level captures, but the digital industry has made large leaps in advancing the technology of low light sensitivity.
One of those advances has been increasing the voltage applied to the sensor. This has a disadvantage, the greater increase in voltage the more heat is generated within the sensor; heat is captured as digital noise in the shadow areas of the scene.
Heat can be dissipated with Cryogenic Pumps using Liquid Nitrogen.
This option has another disadvantage, a very large increase in weight, and a power source to power the pump. Neither very useful for hand held cameras.
Michael G
May 8, 2015 14:37:33 #
Math78 wrote:
The short answer is no - the physics is different. But digital sensors also have a low light problem called signal to noise ratio. At very low light levels, you will not get a good image even with very long times because of thermal noise. That's why some astronomy applications use super cooled sensors.
Averaging multiple images with digital signal processing can increase the S/N by square root of the number of images averaged. Can one decrease S/N with photographs by combining layers of the same image with multiple different exposures, thereby combining different exposures of the same image; effectively adding images with different thermal noise measurements? Might be worth an experiment when I recover from surgery.
May 8, 2015 15:51:49 #
Reciprocity failure caused a colour shift. That doesn't happen in digital. Very long exposures and sensor temperature can cause noise, but that is more akin to film grain than reciprocity failure.
May 8, 2015 16:37:31 #
MCHUGH
Loc: Jacksonville, Texas
Thanks everyone for your informative answers. I did not think this would old problem would apply to digital and everyone confirmed this for me. I sorry for not getting back to check answers sooner. Had unexpected company come in and this is the first time I have been on the computer since posting my question. Thanks again to everyone for the help. UHH never has failed me.
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