Fig. 2
From: Improved BM3D image denoising using SSIM-optimized Wiener filter
The MSE effect on brightness increase: a Original Lena image. b Lena image after adding a constant value of 30 to all pixel values to increase the brightness. c Lena image after subtracting a constant value of 30 from any pixel value less than 150 and adding a constant value of 30 otherwise; the MSE between the images in a and b is equal to 900, while the MSE between the images in a and c is also 900