Modern DSLR cameras are heavily reliant on their autofocus (AF) systems to achieve proper focus. They also suffer from small, dim viewfinders compared to film cameras of years past. To help compensate for this, most camera manufacturers provide focusing screens that are very bright. Unfortunately, these ‘ultra bright’ focusing screens have a very low contrast – they don’t show focus or depth of field well and they do not ‘snap’ into focus when the correct focus is achieved. They also lack any focusing aids, such as split prisms or microprism fields. This makes precise manual focus (MF) very difficult to achieve. And for those photographers doing narrow depth of field shooting or macro photography, for those with large collections of manual focus lenses, and for those times when AF just does not get the job done, precise MF is essential. That’s where KatzEye™ comes in...
KatzEye™ focusing screens are designed and optimized for manual focus applications. The matte surface of the KatzEye™ screen is designed for maximum focus contrast and ‘snap’, and it also provides a much more realistic representation of the depth of field of the shot (when DOF preview or a manual aperture lens is used). With fast (f1.2-2.8) lenses, this high contrast matte provides the maximum feedback to the photographer to help achieve correct focus. And with large amount of light supplied by fast lenses, the viewfinder appearance is also excellent.
However, with the increasing use of compact zooms and telephoto lenses, many photographers find themselves with slower lenses (f2.8-5.6) on their camera more often than not. With these slower lenses, the high contrast matte of the KatzEye™ focusing screens can lead to a somewhat darker viewfinder. To combat this problem, we developed our proprietary OptiBrite™ treatment to improve the brightness of our screens at small apertures or in dim light. The treatment can increase the apparent brightness up to 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, approximately a ½ f–stop increase compared to our standard screens. But, as the aperture gets smaller, the improvement gets greater. By f6.3 the OptiBrite™ treatment increases brightness by well over 1 full f-stop and by f11 it is equivalent to 2 stops or more, when compared to untreated KatzEye™ screens.
OptiBrite™ or Not?
The general rule of thumb in choosing the correct screen is to assess what lenses will be in common use. If the photographer mainly uses fast prime lenses, the untreated screen is the best choice. But if the photographer uses a mix of lenses that includes compact zooms and/or telephotos, the OptiBrite™ treated screen is recommended for best viewfinder appearance.
OptiBrite™ does not affect the prism portion of the screen and is not related to the KatzEye™ “Plus” prism. The OptiBrite™ treatment only affects the brightness of the matte (ground glass) portions of the screen. More information on the “Plus” prisms can be found in the KatzEye™ Plus section. Please be aware that in most cases, the OptiBrite™ treatment does not change the light metering significantly. However, in some cameras the increased brightness of the focusing screen resulting from the OptiBrite™ treatment may slightly affect the camera's light meter – please see the series descriptions for camera-specific details. With DSLRs, 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 KatzEye™ Screens.
If you have any other questions about the KatzEye™ OptiBrite™ treatment, of course feel free to contact us.