Roughly 1 inch white dome diameter, 1 1/4 inch including the black mount.
Roughly 1 inch white dome diameter, 1 1/4 inch including the black mount.
I use a spot meter for incident metering all the time. I don't need no silly luminidiscs either, just my balled fist. My skin is one stop lighter than middle-grey. Compare lighting ratios in a second with the new lumni-fist, not available at finer photo-stores anywhere.
Thebes,
Reading the light intensity off of your fist with a spot meter is a reflected light reading, not an incident light reading.
True, but IF your reflective surface is calibrated and constant then your adjusted reading is equivalent to an incident reading.
It doesn't matter whether you are taking a spot meter reading off of an 18% grey card or your hand.
Although the two types of metering might give the equivalent exposure, you are still reading reflected light, not incident light.
(see: A.Adams," The Negative").
The hand might make a better target than a grey card: as Tim pointed out, a card held at 18 different angles, may give 18 different readings. A hand, IF less shiny and not subject to changes in pigmentation, is more diffuse - will give something closer to a genuine incident reading.
That being said, if we want a diffused omni-directional reading, that problem has already been solved with the invention of a translucent dome. We can mimic it if we try, but mimicry is just... mimicry
Well if you are going to be really technical about it, most incident exposure meters don't read incident light either. Light falls on the dome or disc, then the meter cell reads the light coming from the dome - they don't read the incident light itself. That's not much different from allowing the light to fall on a standard reflector and reading the light coming off the reflector, is it?Originally Posted by Gem Singer
Both methods are basing their measurement on the amount of light incident on the subject, not on the light reflected from the subject.
Best,
Helen
Good point !
At the risk of circular reasoning: if there were no difference - or no appreciable difference - then why would the translucent dome be adopted universally: convenience ? consistency ?
Perhaps it's best to defer to the physicists and Optics gurus on this one.
I think that it is a combination of convenience and, perhaps more importantly, controlled directional response.
Best,
Helen
It seems to me that the disk will remove some of the light reaching the sensor, and thus should be accounted for in some way. My L-718 has a sight hole for reflected average metering, which reduces (using an aperture) some of the light reaching the sensor. It also has a flat translucent diffuser and a dome diffuser that replaces that aperture.
Assuming a diffuser reflects as much light as it transmits, I would expect it to knock off a stop when used on a meter that is not calibrated for use with a diffuser.
Rick "noting that most of the participants have probably long forgotten their participation in this historical thread" Denney
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