How To Optimize Exposure By Exposing To The Right

How To Optimize Exposure By Exposing To The Right

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Exposing to the right (often abbreviated to ETTR) minimizes the amount of noise in your images and helps your camera capture more shadow detail. But what exactly is it and when should you use it? And are there times when you shouldn’t use it? Let’s have a look and see.

Exposure and file format

Do you use the JPEG or Raw format on your camera? Most photographers use Raw because it gives you much better image quality. But it also affects the way you approach exposure.

If you’re shooting JPEGs, you need to get an accurate exposure. You need to keep any over- or under-exposure to a minimum as there’s less headroom for adjusting tonal values in post-processing. For these reasons, you shouldn’t expose to the right with JPEG files.

But is you’re shooting Raw then your goal is different. The idea is to create the best possible Raw file for post-processing. That means one that contains as much information as possible for software like Lightroom Classic to work with. That’s where exposing to the right comes in.

Exposing to the right

Exposing to the right is a technique for creating Raw files with as much shadow detail and as little noise as possible. To understand what exposing to the right is intended to do, we need to understand where noise comes from.

Signal to noise ratio

All digital camera sensors have a certain level of background noise. The amount of noise you see in the end photo depends on several factors, including the signal to noise ratio. Signal, in this case, is light.

Lets say that you’re shooting in bright light, and this gives you an exposure of 1/125 second at f8 at ISO 100. Now imagine that you are shooting the same scene but in much dimmer light. To use the settings of 1/125 second and f8 you need to raise the ISO to 1600.

At this setting, the quantity of light hitting the sensor during the exposure is 1/16th of that in the initial photo taken at ISO 100. There is less signal, and the result is more noise in the final image. That’s the basic reason why there is more noise at high ISO settings than low ones.

The histogram and exposing to the right

Take a look at the histogram below. You can see that the histogram is bunched up in the middle, indicating that I’ve just taken a photo of a low contrast subject.

Diagram showing camera histogram

Exposing to the right simply means increasing exposure so that the histogram is closer to the right hand side of the graph. The increase in exposure means that more light, or signal, hits the camera’s sensor during the exposure, reducing the noise levels in the image.

Ideally you want to get the histogram as close to the right as possible, but without clipping any highlights. If the image is too bright you can darken it when you process the Raw file.

Now take a look at this histogram.

Diagram showing camera histogram

It’s the same subject as the previous one, but I’ve increased the exposure by a stop, which pushed the histogram to the right. Twice as much light has hit the sensor during the exposure resulting in, according to the expose to the right theory, a processed image with less noise.

Does exposing to the right work?

How well does exposing to the right work? Now it’s time to look at the photos to find out. But before we look at the results, there are a couple of points to bear in mind.

First, is that noise levels vary between cameras. Generally speaking, newer cameras are less noisy than older ones, and full frame cameras are less noisy than cameras with smaller sensors. If you have a Nikon D850, for example, you’re probably not too worried about noise, especially if you only shoot at the lower ISO settings.

You can also treat noise other ways in post-processing. Lightroom Classic’s Denoise tool gives amazing results. That means exposing to the right is not the only way of dealing with high noise levels.

Sample images

This is a comparison of the two images that belong to the histograms above.

Comparison of two photos showing how exposing to the right reduces noise

You’re looking at a 100% magnification, and we can clearly see a big improvement in image quality in the photo that I exposed to the right. I developed both images in Lightroom Classic at the default noise reduction settings, using the Exposure slider to darken the exposed to the right photo until it matched the brightness of the other.

Sharp-eyed readers will already have spotted that I took these photos at ISO 25,600. I used this ISO setting as I knew the difference would be quite marked. But exposing to the right makes a visible difference to image quality at all ISOs. It’s most notable when using the Shadows slider in Lightroom Classic to lighten the darkest areas. The more you expose to the right, the less noise there is in the shadows when you brighten them.

Another factor to consider is that in order to expose to the right, you have to increase the exposure, usually by at least a stop. Assuming you keep the ISO the same, this means that you have to open the aperture or use a slower shutter speed, and this may not always be practical, especially if you are shooting in low light.

But, in my experience, you can raise the ISO without increasing noise. You’ll see less noise by using, say, ISO 6400 and exposing to the right than you will by using ISO 3200 and giving the image a stop less exposure.

Test your camera

I recommend that you take some time to test your camera and see if exposing to the right makes a difference to the type of images you take at high ISO settings on your camera. This is the best way to see if the technique will benefit you.

Bear in mind that exposing to the right works when the brightness range of the subject is smaller than your camera’s sensor is capable of capturing. This is most likely to happen when you’re shooting in soft light (like shade) or at the end of the day after the sun has set.

It’s not a technique you can use when the brightness range of the scene is greater than your camera’s sensor can record.

Mastering Exposure ebookMastering Exposure

My ebook Mastering Exposure gives you the knowledge you need to get the correct exposure every time you take a photo. Reading this ebook helps you master your camera’s exposure modes and metering tools, and help you master tools like manual mode. You’ll learn why your camera gets exposure wrong, and how to put it right when it does.

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About Andrew S. Gibson

Andrew S. Gibson is a writer with a camera. He started writing about photography while traveling in Bolivia, and has been published in many prestigious photography magazines including EOS magazine, where he worked as a Writer and Technical Editor for two years. He lives in south Devon in the UK and is inspired by meeting new people, seeing new places and having new experiences. Check out his photography ebooks here.

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