If you sometimes use artistic (painting/drawing/etc.) filters on your photos:
1.  Do you still classify it as a photo or as an illustration?
2.  If you use the filtered image and layer it on top of the photo and apply a certain percentage transparency to give the picture an interesting or highlighted look, does it change your answer if you said that you classify it as an illustration?

For iStock if it's raster, it will be classified as a photo, even if painted from scratch. However, a raster illustration could be keyworded as such.

Other agencies probably have their own rules. I guess you're really asking where the line is drawn. I wonder if that differes between agencies too.

Thank you for your reply. I am not contributing to iStock. I have basically used own discretion over the past 2 years when deciding. If it does not look like a photo any more, I classified it as an illustration. No one ever queried it or changed any of my allocations. But not all images are so clear cut, especially with some effects like HD and others which I only blend with the picture. So I just wandered what others do.