As digital images have become the standard, and with galleries, competitions and publications now accepting digital images, slides have faded into obscurity. With the difficulty of acquiring film, and finding places to process the film, it is simply no longer practical.
This is unfortunate. Transparencies or “slides” of artwork were a glorious thing. When shot with the correct color balance and exposure, they produced extremely reliable color and provided a long-lasting guide for color matching. For example, if I sell a painting and all I have is a digital image, and that digital image is not an accurate rendition of my original (and many are not), then I have no real record of the accurate color. Of course, digital images can also produce reliable color, but it is a much more complex process involving many steps. This is one of those situations where the “old way of doing it” has been supplanted by a newer, more cost effective method, yet the newer method is considerably more problematic for everyone.
Color management with digital images is a very arcane science. Everyone’s monitor displays color differently. And even on the same monitor images will look different depending on what program you look at them in! What’s more, different “color profiles” are attached to different images, which adds yet another variable. Therefore, an artist who photographs and color corrects images on their PC will require a good understanding of the steps in the digital color workflow. Even if that artist did have an accurate and reliable digital image of their painting, there is, as yet, no fool proof method to ensure that those viewing it on the other end, on some other computer, will see it the same way. Transparencies had fewer variables to contend with.