Why my shot in winter has noise as I have an ISO of 200?

Question

The picture below has noise it was a cloudy day, but light was good. And ISO was set to 200. I couldn't find a good reason in my reflection process to know why noise has emerged and what to do in order to take a less-noisy shot in the future.

As you can seen in the picture below there is snow on the right, but the blurred part and even flower itself has noise. Why is this? What should I do to take a quality image the next time.

NB: My Other pictures on the same day has no noise in other places. I have a Nikon d5300 camera. The shot has been taken in 140mm

EDIT:
This is the image info:

Answer 1

Firstly all images have noise. The reason it is more evident at higher ISO is simply that all high ISO does is multiply the signal level, which includes noise. Because processing to a visual form requires a no-linear transform, the darker part amplified become more apparent than they would be unamplified.

It's like you're receiving a radio signal. It will always have noise. If you amplify a weak signal the noise is also amplified.

Also be aware that even in perfect conditions the air is not clean and without distortions and dust. So, for example, the mythical "clear blue sky" is not.

Note that fine grain is left over from low level noise reduction processing. The processing aims to remove colour noise first and generally leaves luminance noise alone. Luminance noise give that grainy appearance. This is done because the eye is more sensitive to colour noise than luminance noise and because removing luminance noise will normally also remove low level detail. It's a balance.

Lastly note that sharpening done in camera will typically exaggerate grain. This is unavoidable using in-camera sharpening, but selective sharpening done in an editor can avoid it.

Answer 2

First off, I don't see the photos as particularly "noisy" to me. Instead they appear over-saturated and over-sharpened. Here are some things to check:

1. Make sure "auto ISO" is not on.
2. Make sure you haven't chosen any "scene" settings (like "Vivid")
3. Check your sharpening/saturation settings
4. Try taking some photos with RAW+JPEG and compare the two

Answer 3

There are a few aspects to your image that highlight the noise, but two things stand out as most important:

1) The color on that picture is very saturated. Whether you're making the adjustment in photo editing software, or you have the camera set to make images very vivid, it is likely to bring out noise a bit more than a neutral image.

2) In your zoomed in example, you are displaying the image at an extremely high magnification, likely equivalent to making a photo print that is on the order of 4+ feet wide! Looking at images from a camera at 100% will show you all the detail the camera/lens/you combination can muster, but in the real world, stuff at 100% really doesn't matter very much.

3) One of the things that brings out noise in an image is actually white balance adjustment, particularly under light that is less than purely white. This could consist of a light bulb, sunset, or anything of the sort. For example, if the light is very blue (As shade is, outside), the camera will make the oranges/reds brighter in order to give the image a more neutral white balance. This will also bring out some noise in those color regions. This is why shady, out of focus areas can appear somewhat noisy at very high magnification.

4) Lastly, you should be happy that your camera is giving you the image, and not smearing all the details to cover up a little bit of noise that nobody actually cares about.