Exposure control in a raw developer: misnomer?

Started Jan 30, 2013 | Discussions thread
hedwards Regular Member • Posts: 268
Re: Absolutely correct.

We should probably stop calling it ISO because it's not really the same thing. It's something that's very different. ISO on a film seems, to me at least, to be the film equivalent of EV compensation as all that does is change the way that the camera decides to request more or fewer photons striking the film. Most of the time, people take the recommendation and use that when shooting their film. But, there's no rule that you can't choose to use the recommended ISO value just because the film box asks you to use that value.

Digital sensors though, are not at present user replaceable, so the misnamed ISO setting is really gain. The sensitivity is roughly equivalent to film of that speed, so the F-stop and shutter speed should be the same to get the same exposure, but it's a completely different way of achieving that.

As far as f2.8 at 1/100 and 100 ISO and F2.8 at 1/100 and 1600 ISO, they're the same exposure as far as I'm concerned. The one at 1600 ISO will be brighter, but the compositional elements will all be the same. But, I can see why one would disagree with that, I think there are valid reasons to consider it to be a part of the exposure as well. I just don't generally make a decision about it, I mechanically choose the lowest ISO I can and usually prefer that over changing my F-stop or shutter speed. The DoF is the same in both cases, although, the circle of confusion is presumably larger in the latter case, they are what I would consider to be the same exposure. Unlike film which sometimes has pleasant looking grain at higher ISO sensitivities, I've never found noise in images to be particularly pleasant to my eye. In both cases it represents a loss of resolution and generally one uses the the least sensitive film one can use.

PS, if anybody works for Sony or Canon reads this thread, user replaceable sensors would be awesome.

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