Why is it important to check that a black image placed onto a black background has the same value of black?
If you take a black image and place it on a black background and the value percentage of black is not the same as the background you will be able to see where the black image ends and the background starts. The blacks will not blend together and you will see a definite line. To ensure this doesn’t happen check the percentage of the black value in your design program to be sure it is set to 100%.