Math Is Fun Forum

Hi,

I wonder if you can help me with this:

I've taken brightness values from a picture using photoshop. These values range from 0 to 255.

I want to turn these values into db which in this case ranges from -100 to 0.

For example, if I get a value of 65 in brightness how can i turn it into a db value ?

Is there a way of doing this ?

Thanks