Great Article On Understanding "Noise"

Danno

Senior Member
I knew a lot about noise already, but this pair of articles really does a nice job of getting to the heart of what noise is, where it comes from, and what affects it and how. Really well put together.

What's that noise? Part one: Shedding some light on the sources of noise: Digital Photography Review
Sources of noise part two: Electronic Noise: Digital Photography Review


Those were good Jake... I am going to have to read them a few times to hold on to the data. Some was a bit hard for me to process but for the most part they were very helpful; especially the summaries at the end of each article. Thanks for sharing... I can tell they're good cause my head hurts a bit... :) stretchin' the tattered brain circuits... :encouragement:
 

BackdoorArts

Senior Member
A very good read...

Further confirmation regarding ETTR, which I try to practice as often as possible, but often fail to remember to do.

For those who might be confused, ETTR = "Expose To The Right", meaning don't leave unused room at the right side of your histogram (but don't blow out the highlights).
 

Spottydumplings

Senior Member
I can tell they're good cause my head hurts a bit... :) stretchin' the tattered brain circuits... :encouragement:

Believe me you are not the only one :confusion:; I don't think that I made it all of the way through the second part!

I did, however, follow the link to the article on "Equivalence" and that is where I really started to get confused. In some places it seems to be at odds with things being said in this article; in this one shot noise is said to be apparent when the "signal to noise" ratio is low, which I read to mean low intensity light where in the Equivalence article Total Light crops up (so to speak). I quote:

"And this means that, for the same shutter speed, F-number and ISO, the camera with the largest sensor will have more total light to measure. And, unless the large sensor is significantly worse than the smaller one, it will produce a cleaner, less noisy image."

My question here is WHY? Surely you could reverse that logic and say that the larger sensor requires more total light to produce the same exposure? You may have more total light but that does not mean that it is going to be any more intense or better quality; just spread wider.
 

J-see

Senior Member
"And this means that, for the same shutter speed, F-number and ISO, the camera with the largest sensor will have more total light to measure. And, unless the large sensor is significantly worse than the smaller one, it will produce a cleaner, less noisy image."

I'd have to read the article but doesn't "measuring more light" here apply to the pixel size of a particular sensor and in that defines the quality of the signal.
 

Danno

Senior Member
Believe me you are not the only one :confusion:; I don't think that I made it all of the way through the second part!

I did, however, follow the link to the article on "Equivalence" and that is where I really started to get confused. In some places it seems to be at odds with things being said in this article; in this one shot noise is said to be apparent when the "signal to noise" ratio is low, which I read to mean low intensity light where in the Equivalence article Total Light crops up (so to speak). I quote:

"And this means that, for the same shutter speed, F-number and ISO, the camera with the largest sensor will have more total light to measure. And, unless the large sensor is significantly worse than the smaller one, it will produce a cleaner, less noisy image."

My question here is WHY? Surely you could reverse that logic and say that the larger sensor requires more total light to produce the same exposure? You may have more total light but that does not mean that it is going to be any more intense or better quality; just spread wider.

I can grasp what the article is saying... but I really struggle trying to explain complex issues like this anymore. I would leave this to some of the others on the forum. I literally struggle to find the words. It has to do with the condition my condition is in. I will defer to others here. Dain Bramage sometimes gets in the way :)
 

Spottydumplings

Senior Member
I'd have to read the article but doesn't "measuring more light" here apply to the pixel size of a particular sensor and in that defines the quality of the signal.

The article is fairly generic and does not mention pixel densities etc.. The preceding sentence states:

"Since the light intensity is the same (per square mm), the Full Frame camera will receive four times as much light as the Four Thirds camera, during those exposures, because it has four times the sensor area, all experiencing that same intensity."

I have read in other posts that the size of the photosites has an effect on noise but if that is the case, to a certain level, should my D90 not be able to match a 24MP FF camera and exceed that of a 36MP D800 as the photosites will be the same size or larger (obviously only for shot noise)?
 

J-see

Senior Member
The article is fairly generic and does not mention pixel densities etc.. The preceding sentence states:

"Since the light intensity is the same (per square mm), the Full Frame camera will receive four times as much light as the Four Thirds camera, during those exposures, because it has four times the sensor area, all experiencing that same intensity."

I have read in other posts that the size of the photosites has an effect on noise but if that is the case, to a certain level, should my D90 not be able to match a 24MP FF camera and exceed that of a 36MP D800 as the photosites will be the same size or larger (obviously only for shot noise)?


It's not only the surface area that counts in terms of noise but the quantum efficiency and the native ISO of the sensor. My D810 as an example isn't that different from the D750 when it comes to photon noise even while its pixels are significantly smaller in surface area. The advantage it has is collecting at 64 ISO which makes up for the smaller surface area.

Btw, out of curiosity I just checked the signal quality of the D90 vs my D7200 and at ISO 200 they're both about the same; 0.8dB difference. The D90 has larger pixels but collects at 200 ISO vs the 100 ISO of the D7200.
 
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