Exposure triangle explanation please.

Started Jul 9, 2013 | Questions thread
texinwien Veteran Member • Posts: 3,326
Re: Not exactly

Guidenet wrote:

I read the article several times and though I respect the writer, I think it is another regurgitated explanation using the Wiki article. I think it analogous with the "The Emperor's New Clothes" tale.

I would like to say that I disagree, but it's stronger than that. This is a question of right and wrong, not a question of opinion, and the writer of that article is simply right, whether you agree/understand or not.

Note, I'm not trying to be disrespectful or in any way rude to you - just telling it like it is.

I think we try to take definitions from physics and try to apply it to a different scenario in photography.

The physics is written in stone and was written in stone long before humans, let alone cameras or artificial concepts like ISO came along.

The idea that it quacks and has webbed feet makes it a duck, might be closer to the mark. When I use my camera, I can use the control of the ISO dial in such a way as to change the saved RAW file.

Assuming nothing else changed when you used the ISO dial (i.e., neither shutter speed nor aperture changed), and that the only change wasn't the ISO value that was saved in the EXIF, your camera is not an ISOless one.

As soon as you switch to an ISOless camera, changing the ISO dial alone (not allowing it to affect any other settings on the camera) will no longer change the saved RAW file, other than the ISO value saved in the EXIF information.

That's a duck, call it what you will. I can also change EV-L or scene brightness and all else being equal, I also affect the RAW capture. I realize this might be brightness applied after the event, but the overall effect is the same. It quacked again. I'm sure it's a duck.

Please clarify.

The idea of ignoring ISO as one of the tools to control exposure seems to be a poor way to both explain it to novice photographers and to understand it in general use as well. Fair enough?

I don't think so. Let's assume the novice can't control scene luminance (he has no flash and isn't in a studio with adjustable lighting).

If he forgets about ISO, he can now focus on the two remaining variables under his control. How is it harder to focus on just two variables rather than on three? I can tell you - it's not. I shoot this way. I ignore ISO and only have to keep two variables in mind. I leave the application of gain (i.e. ISO) until after the fact. That is, rather than the novice juggling three variables before he captures his exposure, I juggle only two and leave the third until later.

Leaving the third until later also means I'm not stuck with a bad gain decision I made at the time of exposure. There is no reason to force the user to choose the necessary gain before he presses the shutter release button. Forcing him to do that makes the act of taking a photograph MORE complicated, not less.

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