Histogram Pixel Area Problem

[smalltrees]

Histograms are a visual representation...
I would consider them far from accurate for your purposes...
why not just enlarge to 1000% and count accurately...

select, isolate on layers, and make large prints... for exact counting...

[Paul MR]

Thats fine IF you are working the size out from a print-out, when working on data resolution is required, the picture requires calibrating as well! Counting pixels is totally meaningless unless you have some means of reference! The Only thing you can do without resolution is work out the percentage of pixels to the whole document.

If there is a scale on the picture, have you resized the picture to reflect the size of the scale if not your area calculations are meaningless?
IE if you measure the scale on the picture in pixels does it give you the same size as shown on the scale, are there any perspective/barrel distorsion parameters to be taken into account?

[Paul MR]

For an insight into measuring a line from a picture see this thread...
Adobe Forums: To scale according to ruler measurement.

[researchdude]

Awesome! I have everything figured out.


So, for the histogram total pixel issue, all I have to do is make sure I uncache the histogram. Photoshop tells you when you need to with an exclamation point in the corner. If you don't, it may mess up the new histogram. I randomly figured this out from reading on a random forum.



As for the Record Measurements tool, I don't think that is in normal photoshop BUT the histogram pixels is the same number. I confirmed this by using CS5 Extended at work and both histogram pixels and Record Measurement area are the same values. This is even better news for me because it confirms that the hsitogram value IS the area of the selection. This allows me to use my conversion to micrometers using the barscale on the image PERFECTLY.


Thanks for all your help!

[hawkeye]

Thanks for sharing the solution.