We have a very high bar for our slide scanners. 35mm and other slide formats have a significant inherent level of detail, and it is critical to have a strong imaging element to get the full sharpness and color depth. This requires multiple different types of equipment for the different sorts of slides we see.
Second, let’s talk about the nuances of the scanners and the situations we need to accommodate when we transfer slides to digital:

Flatbed Slide Scanners: Flatbed scanners are the go-to solution for most of the non-standard slide formats we receive. We have a series of custom mounts, some of which we maintain via 3D printing, to allow us to get the perfect distance from the scanner glass for less common slides. We are using high-end Epson scanners for this purpose where we can go to 4,000 DPI and beyond if necessary. If you send us glass mounted slides, 3D stereo slides or similar, we are likely using our flatbed scanners. When we transfer a slide to digital format, we will also use flatbed scanners for the most common format, 35mm scans, when the slide mounts are damaged, curled or when the film positives must be removed from the mounts to get a good scan. These scanners cost ~$4,000 a piece.

Overhead Scanners: Overhead scanners refer to a sophisticated camera element that images the slides from above. It is relatively uncommon for us to use this scanning rig for slides, but there are exceptions, most commonly oversized transparencies. We built this rig in-house using Nikon imagine elements and it costs ~$20,000.

Tray Scanners: A tray scanner lets you put a series of a few dozen slides into a tray, which are then auto-fed into a high-end imaging element. The best machines for purpose were the converters made by Nikon. Fortunately, we have a huge supply of these devices and know how to maintain them, relying on 3D printing and expert handling. These machines are best leveraged for scanning 35mm slides in standard cardboard mounts. One of our tray feeding slide stations costs ~$15,000.