why subtracting an image from noise (having very low intensity), causes image to loose its maximum value (intensity)

Question

I have set of two image namely main and noise and the maximum value is found using np.max(image_array) function. This will return the values for

• maximum of main image = 1344.056
• maximum of noise image = 34.46

But, when I subtract both image using np.subtract(main,noise) and now, if I find the maximum value of subtracted image, the value is found to be

• Maximum of subtracted image = 1342.312

Now, why the main image is loosing its maximum value from 1344 to 1342 ? Any help in figuring out the issue is appreciated.

Answer 1

Probably the pixel where the maximun value occurred for the image at 1344.056 had a value around 2 in the noise. Thus, when you substracted both then you get a maximun of 1342.312.

If you are substracting both values I supposed your goal is to remove noise from the image and then the one you call image is actually image_and_noise. So, if this is correct the image maximum is 1342.312 and the 2 that was removed belonged to the noise.