Dynamic range can make or break a photo. We explain how to check if you’re capturing all the tones in a scene and ways you can boost your dynamic range.
If you’ve ever taken a shot in sunlight, or any other situation where the brightness range is high, the chances are your camera will have lost some detail in the darkest parts of the picture, the brightest parts or both.
It’s one of the most common photography problems you’ll encounter, but it isn’t to do with exposure. It’s because the difference between the brightest and darkest areas, or ‘dynamic range’, is so great that you can’t find a single exposure that can capture them both.
Digital camera sensors can capture a wide range of brightness values, but there is a limit. If you’re faced with a scene that has a wider dynamic range (or brightness range) than the camera’s, you may well have a problem.
In this tutorial we’ll offer some of our best camera tips and expert advice for recognising, measuring and overcoming this problem. First, we’ll answer some of the most common questions photographers have about using dynamic range in photography.
Page 1 – Common questions about dynamic range in photography
What is dynamic range in photography?
Dynamic range is a way of describing the range of light intensities from the darkest shadows to the brightest highlights. It can be measured in Exposure Value (EV for short) or ‘stops’.
Some scenes have a wide dynamic range, meaning that there is a significant difference in exposure value between the shadows and the highlights – such as shooting a silhouette at sunset – while others have a much narrower range of brightness levels.
When you take a picture, there are actually two dynamic ranges to consider: the dynamic range of the scene you’re photographing and the dynamic range of the camera’s imaging sensor.
Aren’t they the same?
The sensor inside your digital camera can only record a fixed dynamic range in a single exposure. As long as the difference in brightness between the darkest and lightest areas of a scene fall within this dynamic range, you’ll be able to record detail in both areas simultaneously.
For example, if a camera sensor has a dynamic range of 8 EV and the difference between the shadows and highlights is 6 EV, then you’ll be able to capture detail in all areas of the scene.
However, if the dynamic range of the scene or subject exceeds that of the camera sensor, you’ll end up with a picture where the shadows are completely black or where the highlights have ‘blown’ and become totally white – and sometimes both.
Do all camera sensors have the same dynamic range?
No, cameras vary in their ability to handle dynamic range. The greater the dynamic range of the camera, the more info it’ll be able to capture. For instance, the Nikon D610’s dynamic range has been measured at between 13 and 14.4 EV at ISO 100.
How do I know if the camera can handle a scene’s dynamic range?
In the days of film photography, this was a fiddly process. You’d have to take exposure measurements from the darkest and the brightest parts of the scene, calculate the exposure value difference between the two, then check if the film stock you were using was capable of capturing this range of light intensities and how to set the exposure to do just that.
With a digital camera, you can simply review the brightness histogram on the rear screen. This allows you to instantly see whether the dynamic range of the scene (represented by the histogram) fits within the dynamic range of the sensor (represented by the width of the graph).
If the histogram is ‘clipped’ at the edge of the scale, you may lose picture detail – either in the shadows (if it’s clipped on the left) or in the highlights (if it’s clipped on the right). You may need to adjust the exposure to squeeze the scene’s dynamic range into that of the sensor.
SEE MORE: 5 histogram examples of classic photographic subjects
And quite often, you can adjust the exposure, re-shoot and solve the problem. But scenes with a very wide brightness range also produce a very wide histogram – and sometimes the histogram is so wide that it’s clipped at one end or the other, no matter how you adjust the exposure.
The range of tones on an overcast day is quite narrow, producing a narrow histogram. This won’t pose any exposure problems. But the extreme brightness range of a sunny day may produce a histogram so wide that it won’t fit within the camera’s dynamic range no matter what you do.
What’s the answer?
The histogram shows you the range of tones in the whole picture, but not necessarily the ones which you’re most interested in! Sometimes it’s okay to have dense areas of black. It’s fine, for example, in black and white photography.
So by all means use the histogram as a guide, but consider checking key areas of the picture yourself. You can do this using your camera’s spot metering mode to check the brightest and darkest key areas in the picture to see if there’s a single exposure which can capture them both.
Alternatively, you can shoot raw files. These capture up to 1EV of extra shadow and highlight detail that you can extract later in your raw conversion software. You won’t see any sign of this on the camera histogram, though, because your camera will display a processed JPEG preview of your image for display on the LCD, even if you’ve shot in the raw format.
You still have to get the exposure exactly right, even if you shoot raw, but the slight extra leeway might be all you need to capture extremely dark and bright tones in the image.
Sometimes, though, even shooting raw files won’t be enough, and this is where you enter the world of HDR photography.
Can I use exposure compensation to improve a photo’s dynamic range?
No: your camera’s exposure compensation feature only affects the overall brightness of an image. It enables you to shift the histogram left or right along the scale to ensure that either the highlights or the shadows aren’t clipped, but you won’t be able to increase or decrease the dynamic range itself.
If the dynamic range of a scene is too wide to capture in a single exposure – with both the shadows and the highlights being clipped – you’ll need to decide where it’s better to capture detail, and adjust the exposure accordingly.
It’s usually preferable to ‘expose for the highlights’ – in other words to reduce the exposure to ensure the brightest areas aren’t clipped. However, there are some camera settings that can help you improve the dynamic range.
Which camera settings are those?
You’ll get the best dynamic range performance from the sensor if you shoot at the lowest ISO setting using your camera’s raw file format. Raw files hold more information than JPEGs and they offer more exposure latitude, making it easier to pull back detail in pictures that are either too bright or too dark.
Most cameras offer an automatic dynamic range enhancing mode, such as Nikon’s Active D-Lighting or Canon’s Auto Lighting Optimizer. These brighten up shadow areas for a boost in the recorded dynamic range, although they only work with JPEGs.
Finally, as the name suggests, High Dynamic Range (HDR) photography enables you to substantially increase the effective dynamic range. Rather than trying to squeeze the dynamic range of the scene into one exposure, HDR requires several identical images to be recorded at different exposure value levels.
These images are then combined in special HDR software, such as Photomatix, to give a much wider dynamic range than is possible using a single exposure. Some cameras have an HDR mode that can carry out this process automatically for you.
HDR is an easy effect to overdo. If it’s not your cup of tea, you’ll have to use an alternative technique to reduce the dynamic range when faced with a high-contrast scene.
What techniques are those?
Flash and reflectors can brighten up shadows where detail would otherwise be lost. Landscape photographers use neutral-density graduated filters to do the reverse, ensuring detail is not lost in bright areas.
ND grad filters are clear at the bottom and dark at the top; by positioning the dark half over a bright sky, you can bring its exposure value closer to that of the darker foreground.
These days, landscape photographers are just as likely to take two photos of a scene – one that’s exposed to retain detail in the sky and another which has been exposed to retain foreground detail – then combine the two photos in Photoshop or similar software.
Page 2 – Which scenes cause problems for Dynamic Range
Backlighting
If you’re shooting into the sun or any other bright light source, the side of the subject facing the camera will be in shadow – there’ll be a huge brightness difference between your subject and the background.
Bright skies
Overexposed skies spoil landscape shots. On overcast days, the sky can be many stops (EV) brighter than the scene you’re photographing. A graduated filter will bring the sky within the camera’s dynamic range.
Interiors/exteriors
The difference between a window-lit interior and a daylight scene outside will almost certainly be too great for a single exposure. To show any detail through the windows, you’ll need to use HDR techniques.
Light sources in the frame
If you include light sources within the frame, the light source will be too bright to record at an exposure which renders the rest of the scene normally. Just accept that this area will be overexposed.
Fixing problems with dynamic range
Landscapes
Typically you’ll end up with two peaks on the histogram: the darker foreground and the brighter sky. You may be unable to capture detail in both areas using a single exposure. An ND grad filter will reduce the intensity of the sky and bring it within the camera’s dynamic range.
Backlit portraits
When you shoot in front of a bright background, you may find that if you expose the face properly, the background will be too bright. Expose the background properly, and the person will be in silhouette.
To fix this, expose for the background and use a flash or reflector to lighten the face.
Sun and shade
Sunny conditions can lead to high-contrast pictures, where the difference between brightly lit areas and those in shade will be too large for the camera’s sensor to squeeze into a JPEG image. Switch to shooting raw files, so you can rescue detail from ‘clipped’ areas when you process the pictures on your computer.
Dawn and dusk
The sky can be much brighter than the rest of the scene at each end of the day. The previous tricks can help to cope with the contrast, but may not be enough. The solution is to use exposure blending or HDR photography, taking a sequence of different exposures and combining them in software later.
Page 3 – How to measure the dynamic range
To get the right exposure, you need to know the brightness range you’re dealing with. Here’s how to do it.
Switch to manual
In M mode you can note down the exposure readings and choose how you interpet them, rather than relying on the camera’s ideas about correct exposure.
Choose an aperture
If you select a specific aperture, you only need to change one variable – the shutter speed – to work out the best exposure. Let’s go for f/8.
Swap to spot
Now select the spot metering mode. This takes an exposure reading from a small area around the selected focus point only – so switch to single-point AF mode.
Measure the brightest area
Position the AF point over the brightest area (but not the sun) and adjust shutter speed to centre the exposure bar, here it’s 1/500sec.
Measure the darkest area
Now do the same for the darkest area of the picture and, again, make a note of the shutter speed – this time it’s 1/30sec.
Check them on the chart
If the two readings are no more than 4EV apart (check the table opposite), choose a shutter speed right in the middle – 1/125sec.
Page 4 – Best camera settings for capturing wider dynamic range
01 Shoot in raw
Raw files are typically captured at 12 or 14 bits compared with the 8 bits of a JPEG. One of the many benefits of this is increased headroom when editing your pictures, enabling you to reveal lost shadow and highlight detail and expand dynamic range.
02 Use dynamic range expansion
Camera manufacturers include their own bespoke dynamic range expansion feature, such as Canon’s Auto Lighting Optimizer here. These are good at bringing out shadow detail, and you can adjust the strength if it looks unnatural.
03 Check the histogram
When you view the histogram, bear in mind that what you see isn’t what you get when you’re shooting raw files. The histogram and the image preview are a JPEG representation, based on the settings used when the image was captured.
How to use your built-in HDR mode
01 Adjust the dynamic range
The camera will take two or three pictures in quick succession, then blend them into a single JPEG image. You can leave it up to the camera to automatically decide the difference in exposure value between each frame, or you can adjust this yourself. The higher the EV value, the stronger the effect.
02 Adjust the HDR processing
Because it brightens shadows and squashes highlights, HDR mode can leave pictures looking a little flat. However, you may be
able to tweak the way the final image is processed by the camera, boosting colours, contrast and edge definition to give the final image a more painterly or graphic look.
03 Save the originals
The processed HDR image will be saved as a JPEG. However, some cameras give you the option to save the original source files as well, allowing you to blend the images later in software. The Canon 5D Mark III even enables you to save the raw files, for more precise control.
from digitalcameraworld