I want to compare the "screen brightness" of two images using a template image and an acquired image

[Jgarv743]

Mostly looking for suggestions on the best way to go about this. Im trying to run a test that will allow me to compare the screen brightness of an LCD using a webcam. Essentially i will cycle power on the screen and every so often the screen will be incredibly dim. Im thinking i should be able to use the subtract feature with the two images and if i have a normal screen it should produce a close to 0 result, whereas the dim screen should give a non zero value (pixel wise) but so far have not been succesful.

[ncm]

Can you elaborate on what type of equipment you are using and the outputs of this equipment?

[Jgarv743]

I am using a logitech usb webcam, I actually managed to find a vi that solved my issue! Thanks for the quick response

[ncm]

Glad you found the solution! 🙂

[RavensFan]

Help other people by telling what your solution is!

[billko]

Make sure your camera exposure settings are manual or your webcam will compensate for any kind of brightness variations you have!

[Jgarv743 · Accepted solution]

http://zone.ni.com/reference/en-XX/help/370281AA-01/imaqvision/imaq_light_meter__point/  I used the rectangle version but this block instead of going with a subtraction! Being new to and self teaching labview i often overstep these easier solutions 🙂