"Equivalence" demonstrated: Canon 5D and Panasonic GX1

Started Apr 27, 2013 | Discussions thread
Great Bustard Forum Pro • Posts: 40,768
I guess you could say...

KenBalbari wrote:

tko wrote:

Equivalence isn't about exposure. Everyone knows any sensor with the same exposure values has the same BRIGHTNESS. That is the purpose of exposure - to give the same brightness for any camera. The sole reason for it's existence.

Only if the sensitivity of the films or sensors are the same, if you want to be technical.

Of course, in photographic slang, it has become acceptable to include ISO as part of "exposure" (as in the "exposure triangle") in which case it does refer to image brightness.  In that case though, Great Bustard's version of full equivalence then does also produce equal exposure.

It's only when using the technically correct version of "exposure" that he has to say exposure is different.  But image brightness is the same; there is no "visable" difference in exposure if you boost the ISO until image brightness is the same when total light is the same.

[And I know you understood this, but I got the impression some may have been confused by it.]

...the exposures are "equivalent".  That is, f/2.8 1/100 ISO 400 on mFT puts the same total amount of light on the sensor and has the same brightness as f/5.6 1/100 ISO 1600 on FF, even though the actual exposures are two stops apart, but the effect of the exposures is the same, just as the effect of 25mm on mFT has the same effect as 50mm on FF, and f/2 on mFT has the same effect as f/4 on FF.

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