How to Modify the DA* 60-250mm F4 for Full Frame

By bdery in Articles and Tips on Nov 5, 2017

Pentax’s K-mount has one of the most comprehensive APS-C lens lineups on the market. On the other hand, the digital-era full frame line-up is growing but still small. With the release of the Pentax K-1, many users have taken to testing APS-C lenses to see if they can, in fact, be used on full frame.

With its zoom range, fixed aperture and excellent image quality, the Pentax DA* 60-250mm F4 is a lens that many photographers would have liked to see working on full frame. Sadly, using it in full frame mode without modification leads to dark corners at the wide end and fully black corners at the tele end, as you can see here.

The culprit is a flange on the rear baffle of the lens. Easily accessible, this baffle can be removed, modified or replaced to allow full frame operation.

In this article, we present a step-by-step method to modify the lens, as well as various options to replace the baffle. We also test thoroughly the lens’s optical performance after the modification to evaluate the impact of the change.

Is the modification worth it? Can the 60-250mm be used reliably in full frame mode? Read on to find out!

Modifying the DA* 60-250mm F4 for Full Frame