Crack area determination in thin layer

[edgar]

Hi,

I would like to evaluate the crack area [or the Ratio: A(cracks) / A(total)] of a thin layer.
I proceeded as follows:

 1. File - Open - Image (see Appendix Image1)
 2. Image - Type - 8bit
 3. Image - Adjust - Thresold - (threshold set by Regulator) ->  see Image2.
 4. Analyze - Analyze Particles - Ok (Summarize, Exculde on edges, include holes are marked)

I get 0.010% Area. ( A(cracks) / A(total) ).
This seems to little. I estimated about 4% Area by hand.
What is wrong ?

Thanks a lot!

Best regards
Edgar