Scanjet 4890 with TMA (Transparency Materials Adapter) - Problems with Focus

[kstindc]

I actually have an HP ScanJet 4890 with the Transparent Materials Adapter (TMA) which I am using to scan 35mm slides in paper mounts.

The problem is focus:  Normally, an opaque item to be scanned is placed face down on the glass such that the plane of the image is touching the glass and the normal scan is then sharp and in focus. With the TMA, however, each transparency is suspended about 1/16" (~1.6mm) above the glass. Each 35mm slide film is also sandwiched in a cardboard mount, which raises the film another ~0.3mm above the glass surface. Unless the ScanJet 4890 has a mechanism to adjust the sensor to compensate for the separation between the glass and the film, I don't see how the scan could be correctly focused. When I examine and compare .TIFF and .JPG scans from the 4890 with earlier images from a ScanWit 2720 dedicated slide scanner, the lack of focus is easily seen.

Has anyone else seen this problem or addressed it in some way? I would appreciate any assistance or advice.

Thx,

Stephen Tinius

Myrtle Beach SC

TMA from belowTMA in place with four slidesTMA from above

[Repairatrooper]

You are probably correct that 100% accurate focusing is going to be nearly impossible with this type of setup, unless the depth of field on the scanner is very high. A dedicated slide scanner is going to give you best quality and this type of setup is probably not suited to "high quality" expectations.