Originally posted by jpzk
Seems that you'll soon be the owner of a new K3 ?
Yes but I'll wait for the price to drop down a bit. Although the 100$ show rebate was interesting.
One thing I forgot to write is how 40% better coatings translates in real life. Here's the physicist talking.
Roughly, a glass interface reflects about 4% light. For a lens with say 5 elements, that's 10 interfaces (I'm simplifying a lot). So you get 40% reflection. Not really because all the surfaces after the first one also reflect part of the reflected light back again towards the sensor. But for such a lens, it's safe to say that without coatings, you would get at least (at LEAST) 20% light loss (I'm not taking into account the resolution loss because those reflected light rays do not travel to where they should).
Any half-decent coating will reduce the reflections from 4 to 1%. A VERY good coating (like SMC) can be expected to lower reflections to, say, 0.1% Say the HD is 40% better, that means reflections on one glass element would be about 0.06%. That's over the full visible light spectrum.
For my theoretical 5 elements lens, all things being equal the SMC coating would, approximately, have 1% light loss, with the associated resolution loss. The HD would thus have 0.6% light loss, a small difference, but also slightly improved perceived sharpness (and contrast). Considering the release of a 24MP sensor, this is probably WHY Pentax released the new HD lenses. All because of that new ludicrous-resolution sensor.