There has been discussion about the usefulness of exposing to the right (ETTR) in the internet. I made some tests in order to see myself what it’s all about. The results were so interesting that I decided to tell about them to others too.
The principal of this method is to expose the photo as light as possible without overexposing the lightest areas where you want to show tones. When you expose like this you get more details and less noise to your photos than if the exposure is based on the meter readings in camera. This method is useful with RAW files only.
Finnish photographer Pekka Potka has written an in-depth article about ETTR in his blog:
The problem with ETTR is how to indicate in the viewfinder the over exposure and the areas where it’s going to happen before the photo is taken. In cameras with optical viewfinder it isn’t possible. Some cameras with electronic viewfinders can show a real time histogram. The histogram is usually very small and hard to read and it can‘t show the areas which are going to be overexposed. Olympus has developed a method in which the areas of over and under exposure are shown in red and blue colors in the viewfinder.
But nothing is free. ETTR is made by increasing exposure time with (+/-) –control. It can easily be 1 – 2 EV. You must pay attention to exposure time which can be double or triple.
The effect of ETTR is bigger on higher ISO settings.
I haven’t tried to make scientifically exact results in these tests and I couldn’t have reached them even if I have tried. My only meaning was to make these tests so that I could reliably see the effect of ETTR with my test cameras and different ISO values.
All picture settings in both cameras are set to minimum. They shouldn’t have effect in RAW images, but to be sure. In Lightroom I made exposure, sharpening, noise reduction and white balance adjustments so that the pair of photos taken at the same ISO values had same settings.
The target was a part of our bookshelf. The white rectangle in the photo is the 600 x 400 pixels area in the detail pictures. The resolutions of the test cameras are not the same. That’s why the area in the 1:1 detail images is not quite similar.
I took with both test cameras a pair of photos using different ISO values. I exposed the first photo without any corrections to exposure time (+/-) 0. The second photo I took using ETTR.
Sony Cyber-shot DSC R1
R1 is Sony’s 10 megapixels fixed lens digital camera which looks a lot like a DSLR. It was released in 2005. It has been my very good and reliable companion for nearly seven years.
It’s possible to see a real time histogram in the electronic viewfinder of Sony R1, but it’s just as impossible to use as I earlier told. Even +2 EV (+/-) adjustment doesn’t over expose anything but the shining highlights in the test photo. However histogram shows high over exposure. I think the histogram is calibrated for jpg-images and it’s useless with raw-images.
Viewfinder image of Sony R1
R1, ISO 160
R1, ISO 400
R1, ISO 1600
R1, ISO 3200 (max. ISO)
Whole image ISO 3200. Click the image to see larger version (width 1000 pixels).
Olympus OM-D EM-5
OM-D is a Micro Four Thirds camera with 16 megapixels CMOS sensor. It was released in April 2012. I used 12–50mm 1:3,5-6,3 EZ lens in these tests.
Viewfinder image of Olympus OM-D
In the first (1.) viewfinder image (+/-) correction is +1,7 EV and there are no over exposure warnings in the image. In the second (2.) viewfinder image (+/-) correction is+2,0 EV and the red warning color shows the areas which are going to be over exposed.
OM-D, ISO 200
OM-D, ISO 400
OM-D, ISO 800
OM-D, ISO 1600
OM-D, ISO 3200
OM-D, ISO 6400
OM-D, ISO 12800
OM-D, ISO 25600 (max. ISO)
Whole image ISO 25600. Click the image to see larger version (width 1000 pixels).
The picture quality in both cameras at the highest ISO setting seems to be usable at least in small size, for instance in the internet or as 10 x 15 cm prints. These tests were so convincing that I have no doubt about the usefulness of ETTR.