Most older SLR meters are center weighted, so something in the middle of the frame influences the meter reading more than on the edges. But generally speaking, you need a balance of dark and light to achieve the reflectivity of gray. The newest matrix meters compare what the camera sees to some preprogrammed situational data, and try to make a decision based on that. Generally, they don't require as much compensation for subjects that are not overly dominated by one extreme of reflectivity. For example, the meter in one of my old spotmatics requires about two stops of exposure compensation in a snow scene, but one stop is usually enough to get the K-5 in the ballpark. You have to work with your camera and learn how it reacts to different situations. Rules and guidelines are good, but there's no substitute for experience. Again when it comes to nailing exposures in difficult situations, the gray card or incident meter is the easy way out. Paul On Feb 9, 2011, at 11:19 PM, Walter Gilbert wrote:
> Thanks, David/Collin/Paul. > > I think I understand, now. > > I was thinking that since the snow was so glaringly bright that it would > throw the meter off irrespective of the actual subject -- assuming the > subject isn't the snow itself. > > But, as I understand you all now, as long as there's a dark enough > counterpoint to the snow within the frame, the metering will average out. My > question in that case is, does the ratio of dark to light matter? Say, if > you have a snowy field and a small black dog in that field, taking a photo of > a distant grey object, is that enough to get the correct averaging? Or do I > need to compensate for the dominance of the snowy field within the frame? > > In other words, does the meter average the difference between the darkest and > the brightest objects in the frame, or the total amount of darkness and > brightness in the frame? > > Thanks again, y'all. I do appreciate your patience. > > -- Walt > > > > > > On 2/9/2011 9:18 PM, Paul Stenquist wrote: >> On Feb 9, 2011, at 10:05 PM, Walter Gilbert wrote: >> >>> Thanks for the explanation, Collin. >>> >>> When Paul said to overexpose, I was actually thinking it sounded >>> counter-intuitive -- that you'd want to under-expose in a snowy situation. >>> But, it makes sense now that you explained that the meter "assumes" a >>> neutral grey. >>> >>> So, I'm assuming that in extra-low-light situations, I'd want to >>> under-expose by a couple of stops in that case. >> No. It's not amount the amount of light. The reason you overexpose snow or >> anything else that fills your frame with white is simply because it's white >> and very reflective. Like Collin said, the meter assumes everything is 18% >> gray and reflects the amount of light that an 18% gray surface would >> reflect. So shooting a white subject in low light, you would still >> overexpose. Shooting something totally black, you would want to underexpose >> by about one stop, since black doesn't reflect much light.. Again, using the >> gray card and exposing to the meter reading is usually better in really >> tricky lighting situations. Another alternative is an incident meter, which >> measures the light source rather than the scene. As with the gray card, you >> don't have to correct for the reflectivity of the subject when shooting with >> an incident meter. >> Paul >>> Glad I found this out before getting too deep into the roll! >>> >>> -- Walt >>> >>> On 2/9/2011 8:40 PM, Collin Brendemuehl wrote: >>>> No!!! Always overexpose snow by 2 stops. >>>> >>>> Why? >>>> Because an averaging meter expects a mid-gray tone. >>>> The result will be gray snow unless you open it up, >>>> either with the shutter, aperture, or both. >>>> You can also change to iso32. >>>> >>>> >>>> Sincerely, >>>> >>>> Collin Brendemuehl >>>> http://kerygmainstitute.org >>>> >>>> "He is no fool who gives what he cannot keep to gain what he cannot lose" >>>> -- Jim Elliott >>> >>> -- >>> 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. >> > > > -- > 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. -- 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.
