# How to interpret PSNR value?

Say, I have original image, noised and denoised. By PSNR value I want to find out how good does my denoising algorithm works.

For which pair of the images should I calculate it? I've tried it for original+noised, noised+denoised and original+denoised and got PSNR = 28, 29 and 31 respectively.

What value shall be appropriate?

I'm calculating PNSR as here.

With original image $$o$$ fixed, the higher, the better. If PSRN($$o,d$$) is bigger than PSRN($$o,n$$), you can claim an improvement in the decibel measure. It is difficult to interpret PSRN($$d,n$$), sinceyou compare two more-or-less noisy data.