“Expose to the Right” & relation to ISO Invariance

Started Jun 16, 2015 | Discussions
RogOldBoy
RogOldBoy New Member • Posts: 8
“Expose to the Right” & relation to ISO Invariance

Hi Folks:

I am fairly well versed with Histograms and ETTR.

My basic understanding of ISO invariance is that you can have an exposure set with ISO 3200, or you can use the same shutter speed and aperture but reduce the ISO to 100 and then push it 5 stops in Camera RAW. Each image, made differently, will have roughly the same exposure value, with the +5 Camera RAW image exhibiting better noise qualities.

My question is “How does this then affect the use of ETTR?”

-- hide signature --

All the best,
RogOldBoy
(Roger Buchanan)

Tom Axford Veteran Member • Posts: 4,660
Re: “Expose to the Right” & relation to ISO Invariance

RogOldBoy wrote:

Hi Folks:

I am fairly well versed with Histograms and ETTR.

My basic understanding of ISO invariance is that you can have an exposure set with ISO 3200, or you can use the same shutter speed and aperture but reduce the ISO to 100 and then push it 5 stops in Camera RAW. Each image, made differently, will have roughly the same exposure value, with the +5 Camera RAW image exhibiting better noise qualities.

My question is “How does this then affect the use of ETTR?”

Just to summarise your two methods:

Method 1: Use ETTR to determine a shutter speed and aperture at ISO 3200.

Method 2: Use the same shutter speed and aperture as in (1), but reduce the ISO to 100 and compensate by pushing 5 stops in pp.

Method 2 is definitely not ETTR. The histogram will be shifted about 5 stops to the left and will be nowhere near the right-hand edge (i.e. the maximum recordable light intensity).

Method 1 is generally considered the safest method as the RGB values at each pixel may be recorded more accurately (more bits are used in the, say, 16-bit numbers used for each of R, G and B).

However, Method 2 may sometimes be more convenient if you are unable to accurately use ETTR (e.g. the light levels are rapidly changing) and you think you might need the headroom to avoid overexposure.

The important point about Method 2 is that (for some cameras, but not all), it should give a comparable image with similar noise levels to the image in Method 1.

However, a lot depends on the particular camera used and how it implements the different ISO values. For some cameras the two methods give almost identical results, but not all cameras behave this way.

Hopefully, someone who knows more about this subject may elaborate. There have been several threads in the past on ISO-less cameras (e.g. this thread).

rsn48 Veteran Member • Posts: 7,680
My problem with ETTR

Exposing to the right received a great deal of acclaim when it first came out but has died somewhat of a quiet death.  It has disappeared into the shadows not so much because it is wrong, it isn't, its right.  But it works more for static and studio settings.  If you shoot action, whether street photography, sports photography, wildlife photography, these types of motion and speed scenarios, you set up the camera often as quickly as you can and shoot.  If God answers prayer, you have a great exposure, sometimes God doesn't answer prayer and you have the dreaded "blinkies" to contend with, or less than dramatic under exposure.

What I'm saying is if you have the time to set up exposure as best you can, lets say landscape; you can be a budding ETTR enthusiast.  But come out with me when I'm shooting night street photography and lets see how well you can ETTR.

-- hide signature --

Given the choice between excellent equipment and excellent skill, I'll go for the skill every time.

Tom Axford Veteran Member • Posts: 4,660
Re: My problem with ETTR

rsn48 wrote:

Exposing to the right received a great deal of acclaim when it first came out but has died somewhat of a quiet death. It has disappeared into the shadows not so much because it is wrong, it isn't, its right. But it works more for static and studio settings. If you shoot action, whether street photography, sports photography, wildlife photography, these types of motion and speed scenarios, you set up the camera often as quickly as you can and shoot. If God answers prayer, you have a great exposure, sometimes God doesn't answer prayer and you have the dreaded "blinkies" to contend with, or less than dramatic under exposure.

What I'm saying is if you have the time to set up exposure as best you can, lets say landscape; you can be a budding ETTR enthusiast. But come out with me when I'm shooting night street photography and lets see how well you can ETTR.

That's a good point, I agree with you entirely!

In those situations where ETTR isn't really workable (and I agree that such situations are very common), then you fall back on judgement and experience.

It is in exactly those circumstances that it may be worth using ISO invariance (if your camera has a reasonable degree of ISO invariance). In other words, choose to deliberately underexpose (by reducing the ISO sensitivity if it is not at its base level) to allow sufficient headroom for any highlights that may be a bit brighter than you expected (and then adjust brightness in pp).

If your camera is ISO invariant (to the degree required), then deliberately underexposing and then correcting in pp may be a better strategy than guessing what you think is most likely to be the correct exposure, but risking clipping the highlights if your guess was wrong.

CheleA Regular Member • Posts: 269
Re: My problem with ETTR

I discovered ETTR about a year ago and have become a great fan of it!  With that said, I can see(and agree) with the points mentioned above.  I'm lucky in that my style/preferences allow for a slow pace, as well as consistant lighting.  ETTR did help me understand "proper" exposure a bit better.  Obviously, the disadvantage, is that it lengthens/complicates the process as it requires PP.

Keyboard shortcuts:
FForum MMy threads