ETTR summary plus a real example

Last Update:- 24th May 2024.

Much has been written and said about ETTR. Enough for most photographers to see the value in having this technique. Unfortunately, this is not the case because YouTube and forum experts continue to make wild claims about sensor size. This resulted in a powerful exposure technique being lost in a cloud of "size and capture" confusion. This article gives a brief overview of marketing.

This article discusses the 7 points photographers should know about digital cameras.

Olympus EM1 II with Leica 25mm f1.4 lens - ISO6400 f7.1 1/13Sec with ETTR - Enhanced Raw file converted in WorkSpace and edited in Photoshop.

What is ETTR or Exposing to the Right?

ETTR means the best possible aperture, shutter speed, luminance, and ISO mix. The goal is a higher SNR and a saturated image sensor. The ISO function does not control the reflected light exposing the sensor, whereas the shutter and aperture physically control the reflected light. Enough reflected light means a saturated sensor, higher SNR, more tonal data, and better image quality. This article discusses luminance, illumination, reflected light, and the direction and types of light.

What is the role of the ISO function?

We manage 4 of the variables in the exposure formula. These are the aperture, shutter speed, ISO, and luminance. The ISO does not change sensor sensitivity. It amplifies the image signal and the noise coming from the sensor. See my other articles for more about the sensor's noise floor.

I use a fixed ISO to match the ambient light in buildings while adjusting my aperture, shutter speed, and luminance (flash) mix to find an optimum exposure to saturate the sensor. Study this article for more about the ISO, aperture, shutter speed, and illumination. This article reviews the ISO as an image signal amplifier or brightness adjustment. One can also use the ISO strategically...

The most critical variable impacting image quality is understanding the ISO. 
Avoid Auto ISO settings and learn how to manually set the ISO.

What are the benefits of ETTR?

The many senseless "discussions" about photons, bigger pixels, and sensor size mean nothing if it doesn't improve your existing camera. The only variable we manage is sensor saturation. The average consumer camera records more tonal data (image quality) with a saturated sensor. Digital cameras typically double the tonal data for every 1EV of ETTR. That means the histogram moves to the right, the sensor's Saturation and SNR improve, and the camera processes more tonal data.

The under-exposed version has approximately 75% less total data.

How does one apply ETTR?

I only use ETTR for challenging situations. A fixed Exposure Shift of up to 1EV is often enough. I also prefer Aperture or Shutter Mode with a fixed ISO. For example, an ISO of 64 or 100 is perfectly OK in most daylight conditions. I also use my ISO function strategically because we know it adjusts image brightness and is part of the exposure formula. A fixed ISO lets us use exposure compensation for ETTR while monitoring the sensor's saturation and SNR levels with the histogram...

A copy of the Olympus EM1 II display when the camera selected the exposure.

Olympus cameras use a built-in safety Headroom to prevent the sensor from clipping. For example, the camera's exposure meter shows a correct exposure while the sensor is not saturated. It's possible to manage this safety headroom with ETTR. For example, one can increase the exposure by up to 2EV with the blue sky as the background. Another scene might limit the possible ETTR compensation to 0.5EV steps. The camera's exposure meter will show an overexposure reading with ETTR. We correct this in Workspace with the exposure compensation (ISO) function.

Study the image below. I used an ETTR of 1EV. There was enough available dynamic range to increase the exposure with another 1EV. This is how much the camera meter undersaturated the sensor. The processed tonal data in the shadows suffer most in these conditions...

A copy of the Olympus EM1 II display with an ETTR of 1EV.

General comments

Photographers are told that ETTR only works at the camera's base ISO. I disagree because digital cameras are designed to capture more tonal data with the histogram to the right, irrespective of the ISO value. Social media "experts" argue the dynamic range is too little at higher ISOs. The dynamic range does reduce at higher ISOs. Does this mean we shouldn't use ETTR, or should we simply manage the situation? A workable solution is to ignore these paid experts (promoters) and improve your know-how while having more experience from photographing regularly...

Tip:- The ISO effectively adjusts image brightness and not the exposure.

In terms of exposure, the following basics are critical:-

• The aperture and shutter are the only variables controlling the light to the sensor
• The ISO function only amplifies the image signal coming from the image sensor

Do this quick ETTR experiment:-

• Find a scene with deep shadows and not overly bright areas.
• Set the camera to A, S, or P Mode with Auto ISO and take an image.
• Use the above camera settings (fixed ISO) for a 2nd image in Manual Mode.
• Use your aperture or shutter speed to increase the exposure in 0.5EV steps.
• The histogram shows what's happening on the sensor with a fixed ISO.
• Download the images to your PC and study the shadow areas for noise.

Conclusion

The camera's histogram tells us when the image sensor is desaturated at base ISO or when the camera uses its DR safety area. This "safety headroom" is one of the main reasons for M43 cameras having visible shadow noise. Knowledge and experience taught me it's safe to overexpose Olympus cameras with up to 1EV (ETTR) and correct it in Workspace. The secret is a fixed ISO and watching the histogram for highlight clipping while applying ETTR (adjusting the aperture/shutter).

The most important aspect I learned from my M43 journey studying sensors, testing Olympus cameras, and writing articles is image noise has become an effective counter-marketing strategy to discredit the M43 photographers. I recently tested the impact pixel area has on 15 different cameras. The shadow image quality differences were surprisingly small. You will find the article here.

Do I often use ETTR? I have many Olympus cameras in my collection. I photograph almost every day with one of them. I regularly try something new and use these cameras while preparing my articles. I am confident the Olympus engineers selected excellent 16MP and 20MP sensors. This means these sensors perform well in a wide range of applications. I occasionally apply ETTR but found that my understanding of Olympus cameras is more valuable than focusing on noise and ETTR...

Sony A7 III with 50mm, f1.8 lens - ISO25600, f7.1, 1/30sec, and ETTR - The Raw file was edited in PhotoLab 3 plus PhotoLab 3 noise reduction.