Why are my photos noisy - discussion

The alchemy of turning uncertainty into certainty is very attractive.

ok, I think I'll just go back to Plan A and just remember that to minimise visible noise I need to maximise the SNR in my raw data by maximising the exposure* within my artistic constraints and without clipping highlights without having to understand the nuts and bolts of what SNR actually is in detail.

* exposure - amount of light that struck the sensor per unit area while the shutter was open
** optimal exposure - the maximum exposure* within dof and motion blur requirements without clipping important highlights.
*** under exposed - more exposure* could have been added with the DOF and blur constraints still being met without clipping important highlights.

I typed "photosites" or so I thought. I fixed it in an edit.

Yes, intuitively, I would think that spatially there are too many outliers.

Alex Tutubalin wants to ask you - is it possible that your noise reduction software changes good data to bad?

Yep 😊 😊 especially to software manufacturers. Some do it better than others but that is not what this thread is about so let's not go there please.

While they have the same units and can be divided, they are still different animals. First, there are some assumptions: a signal of constant amplitude, and additive zero mean noise. The "additive" is not true even for shot noise but there is a way around it. Then S is the mean, and N is the standard deviation of the noise typically. Not the "level"/mean of the noise, which is zero by assumption.

I agree that the discussions are more advanced than necessary for beginners. However, it is often hard to put yourself in other people's skin (knowledge-wise). Therefore beginners need to ask questions about unclear explanations so that knowledgeable people understand what needs to be adequately explained.

So, please tell us what is not clear to you.

David,

The summary for "how to minimize noise" is all in the first post

1. Maximize exposure:
   Aperture as wide as possible unless you need it set narrower to expand depth of field
   Shutter speed set to the lowest value consistent with acceptable subject movement
   Add light if appropriate and practical

2. Adjust ISO to achieve acceptable image lightness, but not so high as to blow out the bright areas of the images. That's much more important for JPGs than for raw.
   (or just use Auto ISO, perhaps with a bit of negative EC for safety.

The rest, as they say, is commentary
Sherm

A successful answerer does need to be able to adopt the mindset of a beginner. As far as noise is concerned, beginners may not even notice it. But when they do, the question is likely to be: "What can I do to avoid the speckly effects on the black parts of this photo?" The appropriate answer might something like be: "Those speckles are noise and are due to not enough light entering the lens. The way to avoid, or reduce the noise is to do this." (Better illumination is not a good answer, as it may not be possible!) Of course, an acceptable answer may not be possible without asking for more details of the settings that were used.

The signal to noise ratio of this thread is far too low!

David

You are adding to the noise :). The main point of this thread is to explain why photos are noisy, not how to explain properly.

You wrote the following:

What is not clear about setting ISO on Canon R6? For knowledgeable people to give a good answer, they need to have a good question.

P.S.: Sometimes, finding the right question is harder than finding the right answer.

Today's beginners are not using Kodak Brownie cameras, they are using highly sophisticated devices, like the canon R series. They are faced with more buttons, knobs and menu choices than they know what to do with. Thus the best advice is for them to start by setting the camera to automatic. On my R6, choosing A will set exposure and a simple focus mode. The first question that the beginner is likely to pose, is "how do I make the camera focus on Aunt Sally, rather than choosing to focus on the bookcase?"

In fact, one of the best night photos I have taken was done with the automatic night scene mode on my RP, which I believe combines multiple shots, and thus reduces noise.

Proceeding from there it would be good to deliberately take some lousy photos, with the controls set inappropriately. Then take the same scene with controls optimised. In this way, one can show, not only noisy photos, but blurred photos, too light and too dark photos, etc. The comparisons need to be very obvious.

Remember that a picture is worth 1000 words, particularly to a beginner, and an area might be set up here that demonstrates how to avoid these mistakes, and explains the controls. For the Canon EOS R, I always recommend the series of cheap Ebooks written by Nina Bailey. I dont always agree with all she write, but these books can take a beginner a long way in the right direction. She does not talk down to her audience, but explains things simply without any theory.

David

Are you a beginner, or are you explaining what a beginner would ask?
IMO, to get back on track (OP), we need beginners asking questions, not advanced users figuring out what a beginner would ask.

OK, if I am not wanted here I will go away!

David

I have an ebook from Nina (R5). It is not a good book to learn the fundamentals. I have issues with her use of the exposure triangle to explain how to set proper exposure, as well as saying that ISO changes the sensitivity of the imaging sensor to the light. There are other issues as well.

I do not follow, I did not mean to attack your post.
Though, I wish some other posters would have that attitude 🤣.

That's why someone in the DPReview forums had the phrase, "Beware of correct answers to wrong questions" in their .sig.

Nikon Sony canon Olympus Pentax adobe web sites and the list goes on all agree with the ebook. maybe you dont understand the context of the word exposure. is shutter part of exposure when freezing motion with flash.? sensor sensitivity ,look where the voltage that records the image comes from in the sensor circuit. also look at the dual isocircuit it does control sensor sensitivity, I suggest you dooooo some home work. and find out for your self. Have you ever recorded with a microphone ? the mic gain /pre amp controls the mic sensitivity. you wouldn't have a recordable sound if it didnt. the gain control /pre amp is not the volume control on the PA amp. you need to make a distinction between sensor = assembly, sub-assembly and components eg: photodiode. no one is saying that iso controls the sensitivity of a photodiode but rather the sensor.