Adding to Michael's comment about illumination I would suggest you include a standard in every imaging session. By imaging and measuring each time you will have better confidence in the results.
On Wed, Feb 28, 2024 at 4:50 AM Michael Schmid <[email protected]> wrote: > Hi Andre, > > for color images, the "standard" histogram display depends on the > setting of Edit>Options>Conversions>Weighted RGB Conversions. > > If this option is on, the intensity on the x axis of the histogram plot > is calculated as 0.299*R + 0.587*G + 0.114*B and labelled "Intensity > (weighted)". > If "Weighted RGB Conversions" is off, the intensity is calculated as (R > + G + B)/3, and labelled "Intensity (unweighted)". > > In "R+G+B" mode, the histogram shown is the sum of the histogram of the > histograms of the individual channels, i.e., the value for intensity 0 > is the sum of the number of pixels where R=0 plus the number of pixels > with G=0, plus the number of pixels with B=0. You will also see that the > number 'N' of intensity values examined is three times as much as the > number of pixels. > > If you want to examine bleaching, you are probably interested in color > saturation, so you could convert the image to a HSB stack and look at > the saturation and its histogram. > > There are also nice plugins for color inspection, e.g. the 3D Color > Inspector/Color Histogram by Kai Uwe Barthel > https://imagej.net/ij/plugins/color-inspector.html > > Of course, you have to make sure that illumination conditions and white > balance of the camera are always the same. Accurate color measurements > are a science on its own... > > Michael > ________________________________________________________________ > On 27.02.24 19:53, Andre Briscoe wrote: > > Hello, > > > > I am currently working on designing a method to use ImageJ to estimate > bleaching in corals using the histogram function and was wondering what is > being represented in the R+G+B graph in case it is the graph best suited > for what I am trying to do. Does anyone happen to know? > > > > Best, > > Andre Briscoe > > PhD Student > > NSF CREST Center for Aquatic Chemistry and Environment > > Institute of Environment, an FIU Preeminent Program > > > > -- > ImageJ mailing list: http://imagej.nih.gov/ij/list.html > -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html
