Why Exposing to the Right (ETTR) is BAD!

Started Mar 30, 2013 | Discussions thread
Barrie Davis
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Re: Why Exposing to the Right (ETTR) is BAD!
In reply to schmegg, Apr 1, 2013

schmegg wrote:

Barrie Davis wrote:

JulesJ wrote:

Barrie Davis wrote:

Jules,

1) If there is NO free space to the right of the histogram into which ETTR can take place, it is still perfectly possible to increase the signal to noise ratio. It is done by simply exposing at a lower ISO....

-(and, incidentally, doesn't need any messing about afterwards in post processing)-

2) Indeed, the process of ETTR is, itself, only ever "exposing at a lower ISO," even when there IS free space to the right into which the histogram silhouette can be shifted, since the ONLY way to shift that histogram is to use a longer shutter speed or wider aperture...(lower effective ISO)

3) Because of this, photography might as well ALWAYS be done at the lowest (practical) ISO, and this be used as a routine mechanism for reducing image noise....(the stated aim of ETTR)...

-(BTW, it IS what I do, as a matter of course and without having to think about it)-

4)... and nobody need bother themselves with this "Exposing to the Right" nonsense ever again!

I absolutely agree, in fact David Ward also taught us to shoot at native ISO (usually 100) whenever possible. But still doing that Shooting to the Right might still be possible depending on the circumstances and use of f stop and shutter speed. It's not rocket science. It had just been obvious to me until it was brought to my attention. I don't do it religiously now, but I do keep it in mind.

What puzzles me (actually, I am completely mystified) is why people seem incapable of associating exposing to the right with the consequent loss of film speed  (using an effectively lower ISO).

Probably because many people may not use their ISO setting to shift their histogram to the right.

Assuming that the light level is not increased, only increasing exposure (shutter or aperture or both) can expose "to the right." Raising ISO would defeat the intention of lowering noise, since it does NOT increase the signal to noise ratio, but reduces it.

Unless you actually use the ISO setting to shift the histogram, then there is no "ISO effect" on your image - so the concept, whilst being 'interesting', is largely irrelevant.

The whole point is, it is NOT irrelevant. ETTR is, effectively, using a lower ISO. Are you one of those people I was talking about... ?? Or are you just tweaking my nose for some fun...

I have had long ping-pong type exchanges in these forums with posters who just could NOT accept that THAT was what was happened. Quoting the actual shutter speeds and apertures USED at them just didn't help, because they didn't associate THOSE with any particular ISOs, either, it seems.

Why is that, do you think?

Well - I think it's probably useful to consider ISO for what it is - and the only time when ISO settings will have an effect on the image when using ETTR is when you actually change it to achieve the histogram shift.

Oh dear. It isn't about the ISO value you happen to set the camera at. It is about the shutter speed and aperture settings you use to make the exposure. (sigh) It seems you ARE among the ranks of those that have yet to realise that.... when I thought you were kidding around.

Note: I am not prepared to explain in detail why a 400 ISO shot overexposed by one stop's worth of ETTR is actually exposed at 200 ISO. I have learned from bitter experience that anyone who cannot comprehend that simple fact for themselves, will not understand it any better when explained.

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Regards,
Baz
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"Ahh... But the thing is, these guys were no ORDINARY time travellers!"

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