In his latest video, Shelby from Tech Tangents unpacked, installed, and put to use a truly forgotten product: IBM 3119, one of the first consumer flatbed scanners.

The setup was a small nightmare, needing a rare hardware card installed in a specific computer, an ultra-particular combination of two operating systems working in lockstep, and even some careful memory balancing.

Even after all that, a 300dpi page scanner in the late 1980s was still a force to be reckoned with. It’s hard to remember how enormous scanned files were compared to anything else then, even on a black-and-white scanner like this one. The video shows a simple 90-degree image rotation in highest quality requiring over 9 hours, and I believe it.

But deep inside the video, at precisely 19:31, for only ten seconds, something appears that is absolutely worth celebrating. The nascent scanner software has a “curves” feature that allows you to redraw the shades of gray to capture shadows, highlights, and midtones exactly how you want them. Today, the feature would look something like this, with a real-time preview:

There would be absolutely no way to do something like this in the late 1980s, when just rotating an image is an overnight operation, right? And yet:

How was this accomplished? Absolutely brilliantly. Remember the palette swapping technique? Here, the entire screen’s palette is 256 shades of gray. It’s a very particular kind of a linear palette, and so you can easily take that line and… well, turn it into a curve. Since palette swapping happens on the graphic card, it takes as little as one frame of time, allowing for it to react to mouse movements as they happen.

This must have been mind blowing to experience in the moment. Sure, it’s only a preview, and actually applying curves to the image would take many minut—

No. This is a wrong frame of mind. Here’s my hot take: There are moments in software where the preview is more important than the feature following it. That’s because the preview making things faster isn’t just the difference between finishing something sooner or later. It’s a difference of doing something or not doing it at all. Would you even attempt to use curves if each adjustment took minutes or hours, especially in a land without undo?

I love this preview that hints at what the future will be. I like this clever use of extremely limited technology and tight collaboration between engineering and design. It must have been nice to be in the room whenever someone had the flash of insight to use palette swapping this way.