OptiBrite Treatment

Although the Katz Eye™ focusing screens look good and they are bright as they are, if you want the ultimate appearance they can be treated to improve their brightness. We provide a process called OptiBrite which is designed to improve the brightness of our screens at small apertures or in dim light. The treatment can increase the apparent brightness by about 2 stops or more in some conditions. The extra brightness is difficult to quantify exactly due to the subjective nature of human vision, but it tends to increase with smaller aperture. At f1.4, for example, the OptiBrite treatment provides only a moderate improvement — perhaps ½ f–stop equivalent or less. But, as the aperture gets smaller, the improvement gets greater. By f6.3, it's good for about 1 full stop. By f16, it might be equivalent to 2 stops or more, depending on the conditions. It's definitely a pleasant change. For the record though, OptiBrite will not affect the ‘blackout’ phenomenon, where half the prism(s) turn black around f5.6 or so. The OptiBrite treatment only affects the brightness of the matte (ground glass) portions of the screen. If you need small aperture performance below f5.6, our Katz Eye™ “Plus” series of focusing screens will allow split prism performance well past f11. More information on the “Plus” screens can be found here. Please be aware that in most cases, the OptiBrite treatement does not change the light metering significantly. However, in some cameras the increased brightness of the focusing screen resulting from the OptiBrite treatment may slgithly affect the camera's light meter. In cameras that are affected by the treatment, the effect is usually minimal – OptiBrite treatment will typically cause no more than a 1/3 EV shift of the light meter. With DSLR's, it is a simple matter to take a quick test shot, check the histogram, and adjust your exposure compensation as required to ensure that you achieve proper exposures. The OptiBrite treatment costs an additional $55USD on all Katz Eye™ Screens.