Saturday, November 15, 2008

Does the Pentax K20D Perform Better with non-DA Lenses?

by Miserere

When the K20D was first announced, a collective groan went up when Pentax unveiled the pixel count of its sensor. 14.6MP sounded like too many to provide low-noise images with a wide dynamic range. Pentax were quick to calm us down by pointing out that the individual pixels in the new CMOS sensor were actually of a similar size to those of the K10D; what they had done was shrink the inter-pixel space where all the circuitry is located so they could now fit more pixels onto the chip without making them significantly smaller.


They also improved the micro lenses that sit on top of each pixel. By bringing them closer to the surface of the pixel they improved the light-gathering capacity of each pixel because light reaching the micro lenses from different angles will now be better directed towards the pixels instead of being lost in the spaces between them.

While DA lenses have been designed so the light leaving the lens from the rear-most element is as perpendicular to the sensor plane as possible, older lenses were not designed with this requirement because film is sensitive to light coming in from almost any direction. This is one of the reasons why some older lenses don't perform as well on digital SLRS as they did on film SLRs.

All these improvements should help the K20D provide better IQ with non-DA lenses than previous DSLRs from Pentax. If this is true, it would be a very important reason to upgrade for those of us who own a lot of old lenses.

As you might imagine, I don't have a K20D, so I cannot test this myself. It would be interesting if blog readers owning a K20D and one of the other Pentax DSLRs could perform some experiments to show whether Pentax's claims are true or not. Yvon, I know you have both a K10D and a K20D; this sounds like a nice weekend project for you :-) Of course, you'd post the results here for all to see.

I wouldn't be surprised if this were true, and it's another big plus for the K20D that Pentax isn't advertising emphatically enough.

Run some tests, and post your results in the comments section.


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