On Feb 11, 2007, at 7:56 AM, Thibouille wrote: > I know with the D/DS/DL the Optibrite made the camera overexpose > quite a bit. > However on their website, they specificaly say that with the K10 (as > well as DL and K100) their was no metering difference with the > Optibrite. They do not write that for D/DS/DS2. > > Is there any feedback concerning the use of Optibrite screens in a > K10D? I understand the non-Optibrite screen works well. Is the > Optibrite thing really any that good after all?
I think I posted about this a week or two back, but I'll restate it briefly: I have a Katz Eye screen custom made for the DS with no focusing aid .. just simpler markings and a plain matte focusing surface, no OptiBrite. It introduces no differences in metering when used in the DS body compared to the Pentax OEM focusing screen, just gives me a simpler, cleaner framing view with a slightly nicer focusing surface. Since the DS and K10D screens are physically interchangeable, I did a set of metering calibration test shots with the DS, then switched to the K10D. Did a metering calibration test with the OEM screen, switched the screen to the KatzEye and repeated the test. The results showed that the K10D with OEM screen metered a reference neutral gray reflectance target just about right on the money, the DS metered it and returned results about .3EV underexposed. Fitting the KatzEye into the K10D produced consistent underexposure of .7 to 1 EV. I phoned Rachael Katz and discussed this with her. It seems that the way the K10D screen's scatter has been tuned delivers more light to the eyepiece and less to the metering sensors, and the metering calibration has been tuned to that difference for the OEM screen. More light getting to the sensors than expected causes underexposure. The standard DS screen and standard KatzEye screen are very similar in scatter characteristic so produce on-calibration results for the DS metering sensors, but the K10D's metering sensors are expecting less light. The OptiBrite treatment does a similar thing: it tunes the Katz Eye screen's scatter to direct more light at the eye piece which will have the result of reducing the light going to the metering sensors, with a result that the DS calibration curve adds exposure to compensate resulting in overexposure. So the conjecture is that the Katz Eye OptiBrite screen would produce closer to calibration target results more similar to the K10D OEM screen. But of course I'd have to buy one to test this theory out ... and since the advantage I'm looking at is really very small, given the quality of the K10D's OEM screen, I elected not to and will just use the standard screen or Pentax replacement with the reticle crosshairs. The OptiBrite treatment raises screen brightness with a small decrease in focusing surface contrast. Whether that's what you want or not depends upon how you intend to use your camera. I wanted a better surface for manual focusing, that's why I elected not to buy it when I ordered the screen for the DS. Most people buying the Katz Eye screens are buying them to use the optical focusing aids and screen contrast is less important, they just want it bright. Godfrey -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
