Software filter, Photoshop. I usually invert then go through the channel mixer to bring out variations at a higher contrast than what they naturally appear. Sometimes it reveals things that were not visible, but most of the time it just makes it easier to pick out patterns or variations, that is already there, but not easily seen in the un-touched image. For the end user that works the vineyard daily, these high contrast images are a real eye opener.
Comments
I think this is a crop from the orig image. I don't see the yellow?