Creating an HDR effect from a single RAW image
In collaboration with Gilles Theophile
In this tutorial, we will see how to retrieve and use the information in both the bright and dark areas of a single RAW file to create a balanced and realistic image.
To follow this tutorial, you will need:
- DxO Optics Pro 9
- RAW-format images
- You can download our demo images HERE
1- What is HDR?
HDR is the abbreviation for High Dynamic Range, which can also mean “extended dynamic range.” The HDR technique allows you to retrieve and use the information in all areas of the image, regardless of their exposure, so that you can create images with lots of details in the darkest and lightest parts of the image.
HDR images are generally produced by fusing or stitching together images of the same scene shot at different exposures. However, DxO Optics Pro 9’s powerful correction algorithms, combined with the enormous advances in sensor technology and dynamic range of newer cameras, make it possible to recover all the useful information in the different areas of one single RAW file so as to balance an image with drastic contrasts.
While HDR photography carries a strong artistic connotation, this method of restoring the details in the darkest and brightest areas also lets you create perfectly natural-looking images. For example, when photographing a building in the foreground when the sky in the background is very bright, it is almost impossible to expose both the building and the sky correctly.
DxO Optics Pro 9 offers a number of particularly efficient tools in this regard: in addition to Exposure Compensation and Smart Lighting, the Selective tone sub-palette lets you selectively correct the shadows, the highlights, and the midtones without having to merge several images. This means you can achieve an HDR rendering from a single RAW file.
The Selective tone sub-palette
The Selective tone sub-palette, located in the Light and Color – Advanced palette while you are in the DxO Advanced User workspace, contains four sliders that act on different areas of the image:
- Highlights: affects the brightest parts of the image, such as the sky, whites, reflective metallic or water surfaces, etc.
- Midtones: affects the middle or medium areas of the image — that is, the parts that are not overly bright or overly dark.
- Shadows: affects the darkest areas of the image, such as deep shadows, back-lit elements, dark colors, etc.
- Blacks: affects the intensity and depth of blacks in the image.
The Contrast sub-palette
In this exercise, we will also use the Contrast and Micro-contrast sliders in the Contrast sub-palette, accessible in the Light and Color palette. These sliders will let you give more dynamism to the limage, given that manipulating the light can flatten the contrast and render the image dull and lifeless
- The Contrast slider affects the whole image. Moving the slider to the right accentuates the gap between the shadows and the lightest parts, which will result in further darkening of the shadows and brightening of the light parts; moving the slider to the left diminishes the gap. If you significantly increase the contrast, the saturation of the image will also be affected and the colors will also be boosted. Conversely, if you decrease the contrast, the color saturation will be less pronounced.
- Moving the Micro-contrast slider to the right will reveal and strengthen all the textures and micro-details in the image.
2- Example of a dark image
Image content analysis
This photo was taken very early in the morning, with the exposure favoring the highlights, notably the reflection of the sun on the tail of the aircraft. The sky corresponds to the actual scene, but the entire bottom of the image is very dark, to the point where it is difficult to distinguish the ground personnel on the right side of the image.
The goal here is to lighten the bottom without altering the rest of the image, thus preserving the mood of the scene.
Here’s how we will proceed to correct and bring out what is happening in the dark parts of the image.
2.1 – Apply the basic corrections
First of all, we will apply the DxO Standard default preset, which will provide more balance to the image without excessive corrections or other effects. The DxO Standard preset is applied to photos as soon as they are opened unless you change this option in the Preferences.
The original image contains a number of spots and dust specks sitting on the sensor, which the various tone corrections have treated as “details” in the image. You can get rid of them either before you start processing or afterwards.
2.2 – Lighten the dark zones
We will now lighten the zones that are too dark. (We will deal with the brightest zones, such as the tail of the aircraft, on our next pass through.)
Move the Shadows slider to about +30, which will have the effect of lightening the bottom considerably.
2.3 – Adjust the midtones and the highlights
As the aircraft tail was more beautiful in the original image, we can restore it by setting both the Highlights and Midtones sliders to –35, which will allow the recovery of the texture and details in this portion of the photo.
2.4 – Boost the overall and local contrast
These kinds of adjustments sometimes lead to a leveling of the contrast, so don’t hesitate to increase the general contrast of the image as well as that of the details by using the Contrast and Microcontrast sliders in the Contrast sub-palette. In this example, we will set them +15 and +30, respectively.
Even though each slider acts selectively on the different levels of brightness and contrast in the image, all corrections will inevitably have a more or less marked effect on adjacent or transition levels, which is why you will need to readjust the same sliders a second time in certain cases in order to achieve the effect that you want.
Here is the final image that we can produce by using the powerful corrections of DxO Optics Pro (including dust removal and straightening the horizon):
3- Example of a too-bright image
Image content analysis
This is an image of the same scene as in the previous example, but the camera was set to correctly expose the dark zones, which meant overexposing the photo as a whole. We will now attempt to restore the atmosphere of the original, this time taking advantage of the lower part of the image.
Here is how we will proceed to correct this image and restore the ambience of the scene.
3.1 – Apply the basic corrections
As with the preceding example, we will first let DxO Optics Pro apply the DxO default preset. You can see right away that the photo is better balanced in terms of exposure, thanks to the powerful Exposure Compensation and DxO Smart Lightingcorrections.
3.2 – Correct the midtones
This time we will begin by correcting the midtones before processing the brightest zones and then the darkest zones.
Start by setting the Midtones slider to –70, which will make the principal elements in the image — the airplane, the ground, and the people —denser.
3.3 – Tone down the highlights
Set the Highlights slider to –50, which will restore the aspect of the morning sky and enhance the details in the airplane’s tail.
3.4 – Increase the density of the image
To make the photo more dense or darker, move the Shadows slider to –20. There is no point in making the blacks deeper, as this risks making the parts that are already dark too dark.
3.5 – Boost the overall and local contrast
Here again, we can give more depth to the image by using the Contrast and Micro-contrast sliders, which we will set to +15 and +30, respectively.
Don’t be afraid to push the slider settings! The flexibility and reversibility of RAW files give you a lot of room to manoeuvre before having to worry about destroying image data.
Thus we can create a balanced image with only a few clicks.
4- Example of an image that is both too bright and too dark
Image content analysis
This example makes use of a landscape photo taken in bad weather. The goal here is to bring out the sky and the gray clouds, which are overexposed, while lightening the landscape so as to reveal the details — all without losing the special atmosphere of the scene.
One method is to take at least two photos, one at an optimal exposure for the sky, the other for the mountains, and then merge them using special HDR image-processing software. DxO Optics Pro’s processing power lets you achieve an equivalent result more quickly and easily, all without having to rely on an additional software program. This means you stay in a completely reversible RAW workflow.
Here’s how we will proceed to correct the image and enhance the dynamism without going overboard.
4.1 – Apply the basic corrections
As with the previous two examples, the DxO Standard preset will have already done some of the work of recovering the details.
4.2 – Tamp down the highlights
We will begin by setting the Highlights slider to –70, which immediately makes the sky and clouds more present and detailed.
4.3 – Lighten the dark zones
To lighten the landscape without affecting the clouds, we will use the Shadows slider set at +15, as well as the Blacks slider set at +5, so as to limit the clipping to the darkest tones.
4.4 – Enhance the presence and the contrast of the landscape
By setting the Contrast slider at +40, the image will become more dense overall, and that will contribute to reinforcing the atmosphere generated by the bad weather. The Micro-contrast slider set at +45 will bring out the smallest detail while strengthening the impact of the photo.
All in all, correcting this image will have taken less than 2 minutes, including experimenting and making other corrections (e.g., horizon), compared with the method of merging images taken at different exposures, which can easily take at least 20 minutes or more to come up with a satisfactory result.
You can compare the image before and after correction in two different ways, either by displaying them side by side by clicking on this icon in the toolbar, or if you are in single-image mode by simply clicking on the Compare button .
5- Going further: HDR presets
To go further and especially to go faster, you can use one of DxO Optics Pro’s four HDR presets. Just choose one of the following presets from the HDR (Single Shot) sub-menu in section 4 of the Presets menu: HDR Realistic, HDR Artistic, HDR Slight, or HDR – Black & White.
Of course, you can also create presets at any time using your own custom corrections.
Create as many virtual copies of your RAW image file as you want so that you can try different settings and corrections.
Photo credits: Gilles Theophile, Arnaud Pincemin