On Jan 28, 2012, at 7:59 PM, Paul Stenquist wrote: > > On Jan 28, 2012, at 10:31 PM, Larry Colen wrote: > >> >> >> On 1/28/2012 7:07 PM, Paul Stenquist wrote: >>> >>> On Jan 28, 2012, at 9:49 PM, Larry Colen wrote: >>> >>>> >>>> >>>> On 1/28/2012 6:29 PM, Paul Stenquist wrote: >>>>> You can "expose to the right" or anywhere you choose by using exposure >>>>> comp in any metering mode. The metering isn't based on jpeg or RAW. It's >>>>> based on the light and what's in front of the lens. No meter is smarter >>>>> than a photographer who understands how meters work. >>>> >>>> I'm certain that if I'm wrong someone will correct me. The metering mode >>>> in our cameras picks a spot to meter on, and sets the exposure for that >>>> point at midpoint. This means that if you look at the histogram, you >>>> usually get a bell curve right around the middle of the graph, expose to >>>> the middle. This means that if you go direct from RAW to JPEG without any >>>> compensation in post processing, most of the pixels in the photo will be >>>> right around the midpoint of exposure. >>> >>> No. In multi mode, the meter uses a program to analyze the scene and tries >>> to achieve a balance of highs and lows. If you don't like the histogram >>> that results, you can move it right or left with exposure comp. You only >>> get a bell curve in the middle when you have an average scene without >>> extreme highs or lwows. >> >> Interesting. Then why is it that if you photograph something like a white >> table, or snow, using normal metering, it comes out grey rather than white? > > Because the meter is dumb.
That is exactly my point. There's no need for a meter to be dumb when our cameras have more processing power than supercomputers of not that many years ago. > It figures that if there's just one color, then it's midrange. However, > modern meters do a better job than the older ones. The K5 only misses by > about a stop. The older center weighted meters or averaging meters missed by > close to two stops. If I shoot a snow scene with the K-5, I usually give it > about plus one stop of exposure comp. >> >> So, what you are telling me is that the metering in our cameras is optimized >> to give the best performance when shooting in raw mode, rather than in jpeg? > > No, it's not optimized for either mode in particular. It's just a dumb meter. > It measures light and tries to guess what the scene looks like based on its > firmware. >> >> Or, that unlike in film where you'd meter differently for negatives and >> slides, there is no difference in metering for getting the best exposure out >> of jpegs and out of raw? > > You only meter a bit differently for negatives and slides because of the > processing. A slightly overexposed negative can still be printed rather > nicely with more exposure in the enlarger, but an overexposed slide is junk. > When my processing was set up right, I usually exposed about the same for BW > film and transparencies -- or slides if you wish. >> >> >>> >>>> >>>> What it does not do is look at the pixels out at the tail end of that >>>> graph. If a bunch of them are off to the right, and you expose for the >>>> middle, then you end up clipping on a lot of your readings, in other >>>> words, you'll lose highlight detail. >>> >>> Then you bring that back in by dialing in negative exposure comp. >>>> >>>> Alternatively, if most of the readings are to the left of the point that >>>> is metered for, then exposing for the middle will leave you with either a >>>> lot of pixels that are clipped black, or a lot of your shadow detail lost >>>> in the noise. >>> >>> Then you dial in positive exposure comp. Simple. >> >> Why not have a mode in the camera that does it automatically? Give me the >> source code for the K-5 and I could probably implement it in a week. > > You'd have to invent a meter that could tell the difference between gray and > white. Today's meters just read light levels then compare them to firmware > that tries to predict shat part of the scene is sky, what's grass, what's a > face, etc. They don't really know what color things might be or how much > light they are capable of reflecting. But the human brain and the human eye > can make that call with precision. So determining how much exposure comp you > need based on your own intelligence is the best way, and it will probably > remain the best method for many years to come. Or, you could have the meter read all of the metering points, take a look at the brightest, and dimmest, as well as the focusing point, apply a few thousand cpu cycles and come out with something a lot better than what we've got. Or, you could have a special mode that uses the sensor as a light meter, when you'd rather let the camera spend a couple of seconds making the corrections, rather than going through a few test shots yourself. Or, at the very least, as Pentax, you could describe the actual algorithms used so that the photographer wouldn't have to guess what the camera is going to do. -- Larry Colen l...@red4est.com sent from i4est -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
