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Lecture 15: Cameras & Lenses (44)

How are different levels of exposure achieved? I'm thinking that this could be done by increasing exposure time or widening lens aperture.


@SeanW0823, another possibility is to adjust ISO / speed (i.e., how sensitive the sensor / film is to incoming light). Which is "gain" in the next slide I believe.


Is it just me or does the -1 underexposed photo look slightly more natural? I feel like something about the normal exposure is too bright even though it's correct.


joeyzhao123 I think there is no such thing called "correct exposure" as the exposure essentially is a map from (0,+inf) to a value in uint8 (0-255). Depending on your screen brightness, the actual perceived brightness also differs. To "accurately" reproduce the exact light intensity, recent technology such as HDR use more bits than uint8 to represent the perceived brightness.


In this specific example, you should note that human eyes have "auto white balance and auto exposure". Suppose you see this person in front of Wheeler, then you would see -1 when you are standing outside and +1 when seeing from inside the building


Jack brings up a good point about the light intensity representations we use. HDR specifically uses 2-4 more bits than the regular SDR technology we have in most screens and it really does have quite the noticeable difference.

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