ETTR - everything's a compromise [Archive] - AusPhotography:: Australia's Premier Photography Forum::

Dazz1

23-10-2015, 9:48am

Yesterday Mark mentioned maybe using exposure to the right. I had heard of this before, but never really considered it. I read up on it. I liked that it might provide more detail and less noise, and did some experiments this morning. My 600D seems to cope with 2, maybe 2 1/3, stops to the right.

However, there's always a compromise. My big zoom, at 500/600mm allows me f/6.3 max aperture. Using ETTR means that, at any given ISO, I am slowing down the shutter speed. Shooting handheld, as I often do, even with the great optical stabilisation the lens has, I really don't want to get too slow on the shutter - or else motion blur is bound to occur. So, either I increase the ISO (and noise), or miss shots due to blur.

Now, in practice, I am finding I can shoot OK, at 1/200th second shutter speed, at 600mm, with OS switched on, stationary subject, but not much slower. On a typical fine morning, with the subject in the shade in the bush, this means using ISO 1600 or more (and my camera gets a bit noisy at these higher ISOs). To get the ISO back to 800 or less, and keeping above my minimum shutter speed, means forgoing ETTR.

I am not complaining, I knew this was the shortcoming of the f/6.3 limit on the lens. Maybe ETTR is something for tripod use only (for me).

arthurking83

23-10-2015, 11:20am

All things to all people, respectively!

The idea of ETTR is that you capture as much "data" as possible with the camera's sensor.
It doesn't give you a better image in itself, it only gives you a better raw file to work with on the editing side of things.

(note too that all these things change over time as technology improves, which I'll explain my experience later)

So the idea of ETTR, never worked for me, and I mainly do landscapey type photography(or macro) or whatever.
I actually prefer the darker type exposure which gives a more richer colour rendering .. so I hardly ever add saturation to my images, and if do it's minimal only usually to only one colour channel to match the other colour channels brightness or saturation level(s).
But if you use the ETTR principle you lose colour saturation as you view the image, ie. to the naked eye.
So what many people tend to do is to pull down exposure(a lot) or add saturation.
I've tried all those styles of editing and never liked them .. I just prefer the richer colours of a naturally darker exposure. Then there's much less PP work to be done later too.

BUT! ... when I know that ISO is going to be in the higher(than I prefer) range, I then start to use ETTR in those situations.
Higher ISo range is a moving target tho, so there's no predefined ISO level where I use ETTR .. and I don't even think of my adjustment of the camera as a conscious ETTR technique adjustment.
I just know that when ISO is getting to a specific point for a certain camera and in particular lighting conditions, I find that I just naturally set some +ve exposure compensation to counter the effects of noise in the resultant images I'm about to capture.
This is where ETTR comes into it's own, as it's a process to capture the most data in the exposure.
As ISO's start to get higher, the signal to noise ratio(SNR) of the sensor's data starts to decrease if you don't adjust for it.

ETTR is an old technique, and probably more relevant to older tech cameras if low ISO's are being used. It depends on the camera brand/model too tho.

eg. a D800(most new Nikon's actually) can recover about 5 or even 6 stops of shadow data with useful quality. In the old days with older cameras, this may have been 2Ev .. maybe 3 in some conditions. So ETTR was more relevant to those older cameras so as to not produce more noise as the shadows were recovered more and more.

But as we know noise creeps in at higher ISO, so as before the SNR level changes if you don't adjust. By increasing exposure, you're capturing more signal data, and noise data stays the samefor the same ISO level) .. so in effect, the SNR is lower than it otherwise would be.
The more data you capture, the lower the total effect of noise in the image. The same amount of noise level is still there, but all you have changed in exposing brighter is captured more usable data.
How you use that is up to you.

With my old D70s and even the D300 to a point too, to keep noise to acceptable levels in an image at high ISO, I had to expose brighter. This was just experience of reviewing images over the years.
I've noticed this isn't as relevant with the D800E tho up to most sane ISO levels. Of course noise obviously creeps in, it's just that it's not as noticeable as it used to be with the older cameras.

I've tried to use ETTR for landscape images and the images needed a lot of PP work to make them look (what I thought) repsectable. they were wayyyy to bright to start with, not over exposed, just too bright for the actual conditions and feel of the location .. and all I ended up doing is lower exposure by about -1 or -2Ev in editing .. to compensate.
BUT! even in doing this, the image still never looked as nice as the same image just shot 1-2 Ev lower in the first place. Histogram was obviously different and contained much more data in the ETTR image, but the image just didn't look as richly coloured as the darker capture.

ps. the real life difference between f/6.3 and f/5.6 isn't as much as you may think it is.
Try it for yourself.
Set the lens to a lower focal length and f/5.6, and at this same FL, then switch to f/6.3 aperture but maintain the same shutter speed and ISO.
Exposure is obviously darker at f/6.3, but not as much as you think it would be. Vignetting may be more prevalent in the f/5.6 image too tho, so watch for that too.
And then if you like use ISO adjustment to gauge is this slower f/6.3 aperture is actually a deficiency too.
So take the same test as above and keep exposure the same by increasing ISO to suit.
Then compare the two images side by side and note the level of noise in each. I doubt you would notice all that much difference.

Lastly the trick to using high ISO levels effectively is to be sure to capture very sharp images .. ie. to reveal sharp detail.
This is the key to good high ISO images in your selected genre.
If the detail is slightly mushy, then as NR is applied it makes it even more mushy again.
The same is not really as true for sharply detailed areas of an image with NR applied(well, that I've experienced).