Exposure Basics, lesson three?

Started Mar 18, 2013 | Discussions thread
bobn2 Forum Pro • Posts: 57,683
Re: Quick correction.

Najinsky wrote:

bobn2 wrote:

Najinsky wrote:

bobn2 wrote:

The essence of why it's not a good communication aid is here:

bobn2 wrote:

Najinsky wrote:

But later in the course when the different values have become much more familiar, it evolves into something much closer to this as, a recap aid:

from www.wired.com

You've labelled the "ISO' side back to front.

Now, I see you chose to completely ignore that, and instead embark on some rather irrelevant rhetoric. But you they have labelled the 'ISO' side back to front. So, here is a conundrum, a 'communication aid' but one that is communicating the reverse of what actually happens. So, why is that?

The rhetoric . <snipped loads and loads more rhetoric, avoiding the issue>.. hopefully without the 'so why is that?' games.

And we come back to it. In the diagram above, the ISO scale is labelled the wrong way round. There are two ways of looking at it, either one ends up with it being the wrong way round. Either:

i) If you are intending that the other two sides of the triangle be adjusted as the ISO is adjusted. In that case, as you move towards low ISO, the f-number will decrease, so one of the ISO and f-number is the wrong way round, or as you go towards hight ISO the shutter speed will increase, so one of the shutter and ISO is the wrong way round. Taking the majority view, it is the ISO that is the wrong way round.

That was addressed earlier in the thread .

You mean with 'There is no intention to correlate the different sides with each other into a reference or guide by their positioning along the sides. It looks to me like they have simply gone left to right going small to large values.' Actually, with diagrams and communications, in the end it doesn't matter what the author intends, it's what is communicated. And what is communicated is as I said.

ii) If you are intending that the three sides are independent, then we leave the shutter and f-number the same, and adjust the ISO. In that case on the vast majority of cameras the noise will decrease as the ISO is increased.

Either way, the ISO is the wrong way round, yet this diagram is supposed to aid understanding? At best it is useless, at worst harmful. It's rooted in a misapprehension that raising ISO of itself increases noise, which is a nonsense. What increases noise is reducing exposure.

It's neither. As already mentioned, repeatedly, the triangle is not an exposure guide or a definition, it is a visual list of the three settings that the camera chooses when shooting on auto and the three values we need to understand to take the camera off auto and take control. If you don't want to accept that as a role for the triangle, fine, I can live with that.

Again, what is important is not what you think its should be doing, but the message it gives, and for me the message it gives is clearly that ISO, of itself and independently of exposure, raises the noise. That is wrong. And it is a misapprehension that many people exposed to that diagram suffer from. Therefor I blame the diagram. Not an open and shut case, but given that its clear from how its constructed that that message is reasonably to be taken from it, I think it's likely.

You can make ..<snipped, yet more irrelevant rhetoric>.. correctly labled.

What's coming across the more you write about this is someone who's insecure in the basic facts and theory and is unwilling to admit it. That might not be your intention in making these posts, but it's what you are communicating.

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