Hi, Sara - can you post the photo you're trying up upload here? You can click here to edit your question and drag the image into the text area to attach it. Sorry you're having trouble!

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ok, I posted the photo. The photo is uploaded, just won't calibrate. I greatly appreciate any suggestions!

Thank you so much for all your work on this site. A couple girls have been working on a Science Fair project and are stuck on this piece.

I do see an error when I try -- checking out on the server now... thanks for your patience!

Oh sorry, I didn't see that -- will check the calibration now.

Also, would you mind renaming this question "calibration error" or something similarly descriptive? I could also do it for you, if you like (I'm an admin). Thanks again for reporting this issue!

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Of course, please feel free to change it; I can't seem to figure out how.

Also, one last question; in addition to the percentage of intensity, is there a unit for the intensity? Again, many thanks for such a user-friendly program.

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The intensity is not an absolute measure - just a proportion of the dynamic range of the camera sensor. There are a few approaches to correcting for the gain compensation of a webcam, though: #gain-correction -- these should then be able to measure absolute light, though still not measured in lumens, per se -- there are other factors like distance and others that'd have to be considered. This might make a good independent question and I'm sure there are others in the community who'd be better able to answer the question!