In the picture below we can see that the lighting is perfect with least possible noise. What could be the possible settings used to capture this photo or what are the necessary post processing steps taken to achieve this photo?
- Most of the frame is well lit and this contributes to the perception of noise.
- This obviously was done with relatively fast objective, like 85mm F2 on FF or 50mm F1,4 on 1,5x crop or probably somewhat slower (background blur reveals it).
- Yes, the image is denoised. The settings heavily depend on the program which you use.
- The size of image contributes to the percepted noise level. If you saw it printed in full resolution you would probably be not too satisfied. Also, JPEG compression artifacts make noise less noticeable.
I still see traces of noise on darker details of this image.
So, really, a photo like this could be taken by a cell phone camera. There's nothing particularly special. I think it probably wasn't because the blurred background indicates a fast-ish lens and large-ish sensor (but even then, it's not super blurred).
There are three basic things I see which make me say this.
First, it's not that dark. It's an urban scene with a lot of artificial light.
Second, a lot of detail has been lost, probably to noise reduction. That makes everything look smooth — even details that should be there. This could be special software, or it could just be the in-camera setting.
And finally, we're only looking at 640×960 pixel image. Scaling down to that level is inherently a form of noise removal (and one which also, of course, comes at the expense of detail). There's not much pixel resolution left, so all manner of imperfection is masked.
The lens and the camera qualities are an important factor. If you take this shot with a good lens and a high-end camera, there is no noise without any treatment.
If you have to reduce quality on either piece, you will need to process the image for noise-removal (which probably happened here). There is no specific setting to watch for, except having the aperture all the way open. Otherwise, nearly every camera's 'automatic' settings will do what is possible.