<p>Hello,</p> <p>I have two sets of images of vegetation plots taken on an NDVI camera (standard digital camera modified to record red, green and NIR)</p> <p>One set is correct and produces good NDVI values. This set was taken after the camera's white balance was set to a white card which is visible in the image. The other set does not have white balance set (so it was on auto), although white cards are still visible in the images. This second set is currently not usable and produces unrealistically low NDVI values.</p> <p>I am trying to find ways to correct the second set of images. I can do this by matching the histograms, but this only works when matching a 'broken' image to a correct image of the same vegetation plot.&nbsp;</p> <p>My ultimate aim is to be able to correct images of other plots for which there are no correct photos and no white cards in the images, so histogram matching won't work for this.</p> <p>Surely there must be a way to use the white cards to come up with an average change in the channel gains when white balance is corrected. However when I, for example, take the percentage difference between band 1 on the white card in the broken image and in the the correct image for a given plot, and apply this to the vegetation using band math, this still doesn't produce realistic values.&nbsp;</p> <p>Does anyone have any advice or knowledge of any tools for correcting color balance other than histogram matching?&nbsp;</p> <p>Many thanks in advance.</p> <p><br /> </p>