How to tell whether an image has a low gamma (Finding out imaging system tone map)

Question

I am using Emgu C#.

I acquire images from my cameras.

I know when there is no saturation (ie a grey-tone image) by looking at the average hue channel of the image. If zero then pretty sure picture taken at night time.

I can also detect how bright an image is by checking the average Luminescence channel.

What I would now like to do is a value for the gamma an contrast of an image.

Now, I know it is the interpretation of this hypothetical gamma and contrast that determines its value within the context of how I use it. But what factors can i use to attempt to put a scale on these values?

Should I be looking at a different Color Space?

Thanks

Answer 1

You should take a photograph of an object with known color values, such as Macbeth chart:

By using the lowest row of grayscale colors, you will be able to find out the tone-mapping (sometimes incorrectly called gamma) of your imaging system.