Measuring gray & color intensity with ImageJ / FIJI (SEE DESCRIPTION)

Important update (Jan 14, 2023): I have a new video that shows various techniques for better isolating specific colors in **brightfield** images in order to do more accurate comparisons. See here:    • Comparing color intensities between bright...  
Otherwise, if you are just work with images acquired via fluorescence microscopy, this video should still suffice.

You can find the text protocol that accompanies this video on my website: https://sites.google.com/view/kru-neu...

See further down for timestamps to skip to.
Also, if you are working with an image that is a combined phase-contrast (or brightfield or DIC) plus fluorescence image, I've posted a newer shorter video on that here:    • Видео  

In this video, we see how to measure intensity values of selected areas in an image using the ImageJ (a.k.a. FIJI) program. In particular, these values can help you calculate a signal-to-noise ratio.

If you are using grayscale images (or single-channel fluorescence images), remember to go to Image - Type - 8-bit to convert them into 8-bit! This is necessary for limiting the intensity values between 0-255.
This video includes auto-generated subtitles that are not super-precise, so be advised.

0:00 - Intro & displaying my protocols.
2:48 - Explanation of assessing color intensities in a multi-color brightfield image.
18:14 - Explanation of assessing gray (white) intensity in a single-channel fluorescence image.
33:40 - Quick run-through of color intensity analysis.
37:15 - Quick run-through of gray intensity analysis.