Cooke Speed Panchro Lens Colour Temperatures

Vintage series 2 and 3 Cooke Speed Panchro lenses use thoriated glass elements that yellow over time. This can cause colour temperature inconsistencies across a set of lenses as the yellowing occurs at different rates and to different extents.

To measure the colour temperature differences in our set of TLS rehoused S2/S3 Cooke Speed Panchros, we used our lens projector. First we measured the colour temperature of the projector bulb on its own with a spectrometer (5270K). Each lens was then placed on the prjector, and we measured the colour temperature of the light transmitted through the lens.

Here are the results.