This is a follow on post from my original matching grain article a while ago.
This is just one example of how to match grain when replacing a background or perhaps any part of an image.
Look at this image, it is part of a man’s shoulder and the background could do with evening out or replace altogether.
Here I have just selected and deleted the background to white. It does not look at all right.
Above a blur might clean up the background. Whilst evening out the background it still does not match very well.
Here I have added some grain (noise) but it still does not match. If I apply a blur to this then we can achieve a better result.
With a slight blur, it is much better and using the correct selection technique for the original background selection it looks fairly convincing. Using this matching grain technique and varying the amounts of grain and blur ratios and perhaps even repeating the process a few times along with varying the type of noise, we can achieve different patterns of grain to suit nearly every situation.
For a short video on this topic see below.
I am not an advocate or you “must replace the background”. In fact, I’m quite the opposite. The above is meant to show you what can be done if it is needed.