Noise

[HugoSlavinski]

Hi everyone, I just got the Canon RP and I love it. But I got a lot of noise even if I put low ISO... The RP should be useful in dark area but when I look at it on my MacBook Pro it’s very ugly...????

Thank you

[Stephen]

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[shawnphoto]

Oh my bad, did not mean to come across like that all. Just want to assist people in using their gear. I know of course that the RP is actually very good with regard to noise levels, it lacks in DR but is great if the exposure is correct. Anyway, hope it helps!

[ebiggs1]

deleted reply

[jrhoffman75]

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@ebiggs1 wrote:

I fail to see where or why lowering the SS would lower noise. Lowering the SS might even make noise worse if you have to up the ISO to get proper exposure.

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I think you misread - he was advising a slower shutter speed to allow a lower ISO.

[ebiggs1]

Yes I did sorry. Thanx for catching that, john.

[shawnphoto]

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@jrhoffman75 wrote:

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@ebiggs1 wrote:

I fail to see where or why lowering the SS would lower noise. Lowering the SS might even make noise worse if you have to up the ISO to get proper exposure.

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I think you misread - he was advising a slower shutter speed to allow a lower ISO.

Yes, that is basically correct. It is a mistake I have seen many times where photographers adjust ISO for darker conditions, it is usually much better to lower the shutter speed. 

Noise is a fairly complex subject for beginners but as I showed above, even a 6400 ISO image on the RP can be very clean IF it is exposed properly... so do notice the 1/40th shutter speed... The slow shutter speed makes it work, why?

I have several theories on this, first it is a simple fact of more light = less noise. This is related to the SNR of the sensor, staying well above the noise floor is an obvious move.

So, if you have two photos that are underexposed by 1-2 stops, one at 100 ISO at the other at 6400 ISO, due to the reduced SNR at higher ISO with that much of an underexposure you will have nothing but noise. But with 100 ISO obviously the increased SNR will allow recovery.

Therefore it becomes the case that as it gets darker one should lower the ISO somewhat not increase it.

High ISO is mainly for increasing shutter speed (to stop motion) - for GOOD exposures only! 

The other theory I have is one of sampling time. Given enough sampling time the noise in the system will begin to approach a median (a logical assumption for any random input). Essentially by allowing more sampling time you're giving the electronic and photonic variances time to average themselves out. The counter to that is that the longer the sensor is on the more the noise increases, so very long exposures tend to get a little worse than their ISO would suggest.

[ebiggs1]

I doubt your theory is true for digital although it may be true for film. ISO in a digital camera is done by amplification. The sensor doesn't know if you are getting the correct exposure or not. It only knows how much amplification is being applied to it. The fact you may see less apparent noise in a properly exposed photo is noise is often worse in shadow areas, more light equals less shadows.

"...very long exposures tend to get a little worse than their ISO would suggest."

This is true and another reason why your theory isn't valid for digital. Current, amplification is applied for a longer period of time the sensor will begin to heat up. Of course this is only for very long exposures as I can't see the sensor getting much warmer form a 1/500 SS compared to a 1/60.  That is still quite fast!

However if what you believe is working for you go for it. It doesn't matter as long as it is working.

[jrhoffman75]

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@ebiggs1 wrote:

I doubt your theory is true for digital although it may be true for film. ISO in a digital camera is done by amplification. The sensor doesn't know if you are getting the correct exposure or not. It only knows how much amplification is being applied to it. The fact you may see less apparent noise in a properly exposed photo is noise is often worse in shadow areas, more light equals less shadows.

"...very long exposures tend to get a little worse than their ISO would suggest."

This is true and another reason why your theory isn't valid for digital. Current, amplification is applied for a longer period of time the sensor will begin to heat up. Of course this is only for very long exposures as I can't see the sensor getting much warmer form a 1/500 SS compared to a 1/60.  That is still quite fast!

However if what you believe is working for you go for it. It doesn't matter as long as it is working.

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I agree but would refine this a little Ernie. 

The sensor only knows how many photons it captured. That is a function of aperture and shutter speed. Amplification is applied to the signal out of the sensor. 

I don't think many photographers who are shooting in manual mode adjust their settings based on ISO. I know for me the sequence is 1. shutter speed to stop action or eliminate motion blur, 2. aperture for DOF control or pick middle/sharper aperture and then 3. ISO for correct exposure. Noise is the easiest of the image problems to deal with. 

Rick Sammon, who has authored many books and videos, often quotes what his father said (somewhat tongue in cheek) - if you notice the noise in a photo it's probably not a very good photo. 

[ebiggs1]

"if you notice the noise in a photo it's probably not a very good photo."

Good quote. 

[ebiggs1]

"I agree but would refine this a little Ernie."

It was/is a simplistic answer and was meant to be. It is nice that the geniuses that designed digital cameras did so while keeping film characteristics in mind. Us old guys like to compare film specs to digital and most of that works well. New folks that never shot film are not "hampered" by that! Good or bad?

We used to use the ASA number. It is a scale that was made by physically testing and measurements of the film. ASA gave way to ISO which is better for showing the relationship between exposure and sensor output in digital. I don't know if ASA 100 and ISO 100 is exactly the same in photographic specs but I do suspect they are close. You are trying to measure two different mediums and come up with the same answer.

Today we have ISO sensor numbers that go into the many thousands, hundreds of thousands.. ASA film never had that but ASA film did have numbers that went much lower ASA 16 or 12 and even 6, some way back was slower than that.