Interesting. That's a very logical explananation. I suspect I've seen it a lot more than i realize. I may just correct it in conversion without giving it much thought. Because if this shift occurs with the kind of regularity others have suggessted, I must have seen quite a bit of it in 30,000 or so AWB pics. Paul -------------- Original message ---------------------- From: Doug Franklin <[EMAIL PROTECTED]> > [EMAIL PROTECTED] wrote: > > I don't know what's causing that, but I've seen a bit of it as well. It > happened to me in a room with mixed fluorescent and tungsten lighting. Only > once > have I seen it change from one shot to the next. I expect it will go away > with > the first firmware update. > > I've seen it with every digital camera I've used, and even see it happen > to a lesser degree when using "P" or "Hyper-P" mode on film cameras. I > suspect it's a combination of things. One of them is the "slice of a > cycle" issue Godfrey described. > > However, I've seen it happen in a sequence of daylight shots taken > outside in machine gun mode, so I don't think that's the whole answer, > either. > > One thing I think plays a role is going to take me a minute to explain. > > Basically, AWB only has one thing to play with, and that's the actual > content of the image as captured by the sensor and the metadata > describing the parameters of the capture process itself. > > It runs some algorithms on this data and decides what it thinks the WB > should be. I suspect that some of those algorithms involve evaulating > the histogram. That means that changes to the content of the image as > captured can change what it thinks ought to be the WB. > > As an example, look at the first three photos on the page you posted. > > http://users.accesscomm.ca/wrobb/temp/whitebalance/wb.html > > In the first one, it seems like it's picking a "more tungsten" WB. In > the second one, it seems to be picking something closer to "flourescent" > or "daylight". In the third one, it's somewhere in between. > > Now look in detail at the differences in what was captured in those > images. The first one is a bit to the left of the next two, and doesn't > include any of the door. The second one includes just the silver light > switch and conduit and a thin slice of the dark door jamb. The third > one contains most of the door, including that pink poster on it, and > some of the white wall on the other side. > > My guess is that those differences in content are what make it pick > different WBs in a situation like this. > > -- > Thanks, > DougF (KG4LMZ) > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions.
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