Quote Originally Posted by wiltw View Post
Thank you both, Gary and Clive, for providing some reasons for your previous one word opinions of meter suitability.

I tend to side more with Gary in the assessment that "An incident meter has no means of knowing what it is looking at or what it is metering, and furthermore doesn't care." For that reason, if we have bright highlights which would overexpose and wash out detail in the color transparency, we end up with clear base and no details. (The same exposure with color neg would be well tolerated due to it tolerance to overexposure.) Meter the same scene with a spotmeter, and I know precisely how to expose so that the highlights will be captured best on film, and avoid the clear detailess filmbase.

If I shoot for publication, I use the one-degree spotmeter to measure highlights and deepest shadow, to decide placement of my exposure to best capture the full dynamic range of the scene and the midpoint of the range...and that might not match what the incident meter says. Futhurmore, the spotmeter allows me to determine if the lighting needs to reduce the dynamic range to fit within which is achievable on the printed page by the offset press; you can't do that with an incident meter.
The ignorance of meters is universal. Spot meters have no idea about what they are being pointed at either.

As with all things photographic, we each decide where to point our tools and we provide the context needed to make decisions about what to do with the reading. It's the nut behind the camera that makes it work, not the tool in his or her hand.

Way back in time before incident meters got their domes a technique was developed to address the blown highlights problem on transparency film when shooting in high contrast situations, its called duplexing.

Classic duplexing takes two readings: one with the meter pointed "back at the lens", essentially the same as is taught in incident meter manuals today, this reading is to find the "best" exposure for the main subject matter; the other reading is taken with meter pointed directly at the main light source, sun or whatever, this is to find the "best" setting for the highlights. These readings are then averaged, just as is normally done with shadow and highlight readings from a spot meter. (This model makes certain assumptions, like "the mid-tones and the highlights are what we want to protect". If shadows are more important than say mid tones just replace that reading with a different orientation of the meter head.)

In both cases, averaged duplexed and averaged spot readings, a compromise is made. In high contrast lighting when using say Velvia, there is simply not enough film range to get all the highlights and all the shadow detail we might want. Something is going to be lost, both methods simply do their best to find the best balance.

Side note. After incident meters got their domes duplexing for front lit and cross lit scenes became almost unnecessary, the final camera setting is normally the same. Duplexing does still have real value though when the subject is backlit.