Today was my second day shooting with the Pentax 645D. We’re still getting to know eachother. I found out the electronic level is not level (as I suspected the first day already). Since I’m not the only Pentax user experiencing this it probably is behaviour by design, I’ll just put my bubble level in my back pack.
After these few extra hours of usage I’m thinking that the Pentax might actually be a bit easier to focus than my old Canon 1Ds II. When focusing quite close the big viewfinder helps, the few portraits I shot were all tack sharp on the closest eye (@ f/2.8). With greater distances or flat surfaces that are harder to focus some detail that is there seems to “pop” in and out of focus more clearly than I was used to with the Canon.
But what I really wanted to find out was this ISO 100 versus ISO 200 business, so I shot three series of four test shots: first a correct exposure at ISO 200, then I set the camera to ISO 100 and halved the shutterspeed for the second photo (shutter stays open twice as long, should yield the same exposure). Then I shot two more on ISO 100 increasing the shutterspeed by 1/3rd stop each, trying to find out whether it actually was ISO 125 or ISO 160. Here’s one, all four photos taken at f/10:
In my book a shutterspeed of 1/100 on ISO 200 is the same as 1/50 on ISO 100 exposure wise, all else being equal. This is clearly not the case, in stead the exposures look about the same with 1/60 for the ISO 100, which indicates it is actually ISO 125. All three series pointed to ISO 125. Good to know.
I couldn’t find any obvious evidence of reduced dynamic range in ISO 100. It might be there but with my eyes using photoshop at 200% inspecting the lightest and the darkest parts I couldn’t see it. Looking at noise: ISO 200 seems to have slightly more (I had thought there would be no difference for ISO 100 is part of the extended range).
It is an absolute pleasure to take photographs with the Pentax and to review them at home on the computer. The sharpness is stunning. This is hard to show. I have looked at countless photographs with some detail shown bigger and still didn’t think the photographs would be _this_ sharp. But here’s mine.