a900/a850 capture characteristics

[Bruce Oudekerk]

There were a number of reasons I chose an a850 to be my next camera when I purchased one a year ago. Two of them had to do with the nature of the sensor. One is the huge dynamic range that this camera’s sensor can capture but I think the other related issue was somewhat of a fool’s errand on my part. And I think my self-rationalization requires a bit of an explanation:)

One of the problems or characteristics (depending on how you look at it) of digital image capture is the linear nature of the sensor/ associated electronics, as apposed to film, when its output characteristics are plotted vs. light intensity. This last week, I attended a talk by fine arts B&W photographer Guenter Knop and he was stating why he still uses film and not a digital camera. His argument was somewhat unconvincing to me but I was sympathetic to his rationale. Film has a characteristic heel and toe when graphed that demonstrates its resistance to blown out highlights and blocked shadows and thus film can display a much different character than what we typically find in the digital domain.

At any rate, previous to my purchase of the a850, I had noted in reviews that the a900 had a significantly different response curve than other cameras and is much more film like, at least in my remembrance of what the old Kodak film curves used to look like. At the time I couldn’t understand why EVERYONE wasn’t discussing this a900 characteristic as it really set the camera apart. It still does. In hindsight, what was eluding me was how these graphs in the reviews are actually plotted. If they come from in-camera Jpegs, they are totally worthless to me. On the other hand, if they come from an analysis of the RAW data…that’s great. And if that is so, how did these film-like curves come to be in a digital world, what with its intrinsically linear response?

I have been generally very pleased with the headroom and characteristics of the highlights with my a850, but I suppose that could be attributable to a conservative metering. Especially since the in-camera histograms are coming off the in-camera-Jpegs and I usually manipulate RAW.

I guess what I’m looking for here, is a technical clarification of what I’ve read in reviews and am seeing in my images as it relates to a plotting of the response curve. Or for someone to understand my confusion regarding the digital camera light response and set me straight.

Bruce

[Dr. Harout]

Bruce, I've read many times about those characteristics in different places and if I'm not mistaken David emphasized that too, read it on Luminous Landscapes etc.
BTW, a friend of mine who had the joy to handle both cameras (a900 and a850) insists that the latter's construction leaves much to be desired (compared to a900, of course). He had the feeling that it will have the same "skin" problem as the a100 (probably he exaggerated, but I haven't seen them yet with my own eyes )

[Bruce Oudekerk]

I have held both cameras in my hands consecutively and the only thing that is different about the external body housings is that the a850 has a different surface…it’s somewhat more matte. Some have said the rubberized parts are different but I haven’t noticed it. If you are familiar with the shake and spray Krylon semi matte paint, the surface of the a850 is similar to that but with a more micro-pebbly ‘tooth’. However, it’s in appearance only, as the bodies are the identical. Internally the mirror box is similar but not exactly the same and of course the a900 does 5 FPS. I’ve gotten so used to the a850 I don’t even notice the nuances of the surface anymore and if I do…I like it. Of course I have no idea how well the surface will wear…even if it’s all cosmetic wear.

Bruce

[Dr. Harout]

Thanks for this explanation, Bruce. I guess we have to mention all details, even minor as the one dealt with here to help others make decisions. Thanks again.