Daily we help thousands of designers (famous or not) to identify a font they need to complete their work. And sometimes moms looking for a font to make a cute postcard.
Most of the time the search is successful and we have an exact match finding the font from the image you uploaded.
As in any other software tool, the better the input is, the better the output you get.
Bellow, you can see some samples of how the images should look like (or not).
As a rule of thumb, the clearer the image is (clean background, separated characters, black and white, horizontal alignment) the better the results are.