Most people have no idea what “E-6” is. To avid baseball fans, E-6 is the way to record an error by a shortstop on your scorecard. But there is another E-6, in photography. This E-6 is the developer in which color slides are processed.

Recently, I received an e-mail from Chromatics, a photo lab used by professional photographers in Nashville, saying that they will be discontinuing the developing of color slides and color transparencies in general after September 9. This was sent to me as an old customer of theirs.

The passing of E-6 is the passing of an era, because it means that so few professional photographers are using color slides and transparencies these days, in this era of digital photography, that a major photo lab does not get enough of this kind of film to develop to make it worthwhile to stock the chemical that is used.

The films used to make color prints — as distinguished from slides — are processed in a different developer (called C-41), and the market for that is still good. But the biggest reason for the decline of color slides is undoubtedly the rise of digital cameras.

The fact that Chromatics will no longer process color slides in E-6 does not mean that nobody will be doing so. No doubt other photo labs in some other cities will continue to develop color slides and color transparencies — at least for a while.

But the handwriting is on the wall.

To those of us of an older age (80 in my case), this passing of one more icon of our era makes us feel like we are relics of a bygone time. I can remember when I used to develop my own color slides in E-3, a long-ago predecessor of E-6.

Another photographic icon that vanished in recent years was Kodachrome, the film that put color slides on the map. A few years ago, Kodak announced that it was being discontinued. For many years, Kodachrome was the finest color film in the world.

Even after other color films caught up with it, and even surpassed it in some respects, it was still a great film to have, because it did not require refrigeration, as other color films used by professional photographers do. It is a big nuisance to have to take a cooler with you when traveling with professional color film.

The reason for the difference was that Kodachrome did not have dyes in it, like other color films, and it is the dyes that are so vulnerable to heat. Kodachrome was actually three layers of black-and-white film, each layer sensitive to different colors, with the dyes being added later, during the developing process.

It was a more complicated process than developing slides in E-6, and Kodak preferred to develop Kodachrome itself, rather than risk having other processors do a second-rate job that would harm the high reputation of Kodachrome.