The dynamic range (ratio between dark and bright regions) in the visible world far exceeds the range of human vision and of images that are displayed on a monitor or printed. But whereas human eyes can adapt to very different brightness levels, most cameras and computer monitors can reproduce only a fixed dynamic range. Photographers, motion picture artists, and others working with digital images must be selective about what’s important in a scene because they are working with a limited dynamic range.
High dynamic range (HDR) images open up a world of possibilities because they can represent the entire dynamic range of the visible world. Because all the luminance values in a real-world scene are represented proportionately and stored in an HDR image, adjusting the exposure of an HDR image is like adjusting the exposure when photographing a scene in the real world.
A. Image with shadow detail but highlights clipped B. Image with highlight detail but shadows clipped C. HDR image containing the dynamic range of the scene
In Photoshop, the luminance values of an HDR image are stored using a floating-point numeric representation that’s 32 bits long (32‑bits-per-channel). The luminance values in an HDR image are directly related to the amount of light in a scene. By contrast, non-floating point 16‑ and 8‑bpc image files store luminance values only from black to paper white, reflecting an extremely small segment of dynamic range in the real world.
In Photoshop, the Merge To HDR Pro command lets you create HDR images by combining multiple photographs captured at different exposures. Because an HDR image contains brightness levels that far exceed the display capabilities of a standard 24‑bit monitor, Photoshop lets you adjust the HDR preview. If you need to print or use tools and filters that don’t work with HDR images, you can convert them to 16- or 8‑bpc images.
HDR photos are used to capture scenes having a large dynamic range. However, using more number of photos can lead to unwanted artifacts from poor alignment or ghosting. For optimal HDR merge, the aim is to capture photos in a manner that each part of the scene is well-exposed, that is neither blown-out nor under-exposed in at least one of the photos.
- If your HDR bracketing is less than 3.0 stops in total separation (-1.5, 0, +1.5), use only the darkest and brightest exposures to generate an HDR. Capturing the middle exposure, or zero exposure, is not necessary for generating a quality exposure blend in such cases. If you exceed the 3-stop separation between the darkest and the brightest exposures, an additional exposure offset becomes necessary to process a good quality HDR photo.
- If you are a photographer using the ± 1.5 exposure bracket, you can ignore the zero or middle exposure. This helps in faster render and improves alignment odds in the resultant HDR by reducing the chances of potential camera movement between the exposures. However, the zero exposure can be useful in scenarios where the capture scene is within the acceptable range of a single exposure and can be developed independently.
- If you are a standard HDR shooter using a ± 2.0 bracket, you ideally require only three photos to merge into an HDR.
- If you are a 5 shot ± 4.0 stop shooter, you can now drop from 5 shots to 4 shots for merging and processing HDR. However, if you are a 7 shot ± 6.0 stop shooter, you can now get the optimal HDR blend with only 5 shots (-6.0, –3.0, 0, 3.0, 6.0) provided your camera has three-stop stepping in the exposure bracketing function.
Secure the camera to a tripod.
Take enough photos to cover the full dynamic range of the scene. You can try taking at least five to seven photos, but you might need to take more exposures depending on the dynamic range of the scene. The minimum number of photos should be three.
Vary the shutter speed to create different exposures. Changing the aperture changes the depth of field in each exposure and can produce lower-quality results. Changing the ISO or aperture may also cause noise or vignetting in the image.
In general, don’t use your camera’s auto-bracket feature, because the exposure changes are usually too small.
The exposure differences between the photos should be one or two EV (exposure value) steps apart (equivalent to about one or two f‑stops apart).
Don’t vary the lighting; for instance, don’t use a flash in one exposure but not the next.
Make sure that nothing is moving in the scene. Exposure Merge works only with differently exposed images of the identical scene.
You can use the following tools, adjustments, and filters with 32‑bpc HDR images. (To work with more Photoshop features, convert a 32‑bpc image to a 16‑bpc or an 8‑bpc image. To preserve the original image, create a copy with the Save As command.)
Note:
Although the Exposure command can be used with 8‑ and 16‑bpc images, it is designed for making exposure adjustments to 32‑bpc HDR images.
Blend Modes
Normal, Dissolve, Darken, Multiply, Lighten, Darker Color, Linear Dodge (Add), Lighter Color, Difference, Subtract, Divide, Hue, Saturation, Color, and Luminosity.
Create new 32‑bpc documents
In the New dialog box, 32 bit is an option in the bit depth pop‑up menu to the right of the Color Mode pop‑up menu.
Note:
Although Photoshop cannot save an HDR image in the LogLuv TIFF file format, it can open and read a LogLuv TIFF file.
Filters
Average, Box Blur, Gaussian Blur, Motion Blur, Radial Blur, Shape Blur, Surface Blur, Add Noise, Clouds, Difference Clouds, Lens Flare, Smart Sharpen, Unsharp Mask, Emboss, De-Interlace, NTSC Colors, High Pass, Maximum, Minimum, and Offset.
Image commands
Image Size, Canvas Size, Image Rotation, Crop, Trim, Duplicate, Apply Image, Calculations, and Variables.
View
Pixel Aspect Ratio (Custom Pixel Aspect Ratio, Delete Pixel Aspect Ratio, Reset Pixel Aspect Ratio, etc.)
Layers
New layers, duplicate layers, adjustment layers (Levels, Vibrance, Hue/Saturation, Channel Mixer, Photo Filter, and Exposure), fill layers, layer masks, layer styles, supported blending modes, and Smart Objects.
Tools
All tools in the toolbox except: Magnetic Lasso, Magic Wand, Spot Healing Brush, Healing Brush, Red Eye, Color Replacement, Art History Brush, Magic Eraser, Background Eraser, Paint Bucket, Dodge, Burn, and Sponge. Some tools work with supported blend modes only.
The Merge To HDR Pro command combines multiple images with different exposures of the same scene, capturing the full dynamic range in a single HDR image. You can output the merged image as a 32‑, 16-, or 8-bpc file. However, only a 32-bpc file can store all the HDR image data.
HDR merging works best when photos are optimized for the process. For recommendations, see Take photos for HDR images.
Move the slider below the histogram to adjust the white point preview of the merged image. Moving the slider adjusts the image preview only; all HDR image data remains in the merged file.
The preview adjustment is stored in the HDR file and applied whenever you open the file in Photoshop. To re-adjust the white point preview at any time, choose View > 32‑Bit Preview Options.
Note:
The Camera Raw Filter does not work with 32-bit files in the following:
- Adobe Camera Raw 9.10
- Photoshop CC 2017
If you are using one of the above, see The Camera Raw Filter no longer works with 32-bit files to view workarounds for this issue.
HDR images contain luminance levels that far exceed the dynamic range that 16‑ or 8‑bpc images can store. To produce an image with the dynamic range you want, adjust exposure and contrast when converting from 32‑bpc to lower bit depths.
Choose one of the following tone-mapping methods:
Tone and Detail
Dynamic range is maximized at a Gamma setting of 1.0; lower settings emphasize midtones, while higher settings emphasize highlights and shadows. Exposure values reflect f-stops. Drag the Detail slider to adjust sharpness and the Shadow and Highlight sliders to brighten or darken these regions.
Note:
By default, the Toning Curve and Histogram limit and equalize your changes from point to point. To remove the limit and apply more extreme adjustments, select the Corner option after inserting a point on the curve. When you insert and move a second point, the curve becomes angular.
A. Inserting a point and selecting the Corner option. B. Adjusting new point makes the curve angular at the point where the Corner option is used.
Equalize Histogram
Compresses the dynamic range of the HDR image while trying to preserve some contrast. No further adjustments are necessary; this method is automatic.
Exposure and Gamma
Lets you manually adjust the brightness and contrast of the HDR image. Move the Exposure slider to adjust gain and the Gamma slider to adjust contrast.
Highlight Compression
Compresses the highlight values in the HDR image so they fall within the luminance values range of the 8‑ or 16‑bpc image file. No further adjustments are necessary; this method is automatic.
If images have different content due to moving objects like cars, people, or foliage, select Remove Ghosts in the Merge To HDR Pro dialog box.
Photoshop displays a green outline around the thumbnail with the best tonal balance, identifying the base image. Moving objects found in other images are removed. (If movement occurs in very light or dark areas, click a different thumbnail where moving objects are better exposed to improve results.)
Note:
For a tutorial on the Remove Ghosts option, see this video. (Discussion of Remove Ghosts begins at 3:00.)
Response curves indicate how camera sensors interpret different levels of incoming light. By default, the Merge To HDR Pro dialog box automatically calculates a camera response curve based on the tonal range of images you are merging. You can save the current response curve and later apply it to another group of merged images.
- In the upper-right corner of the Merge to HDR Pro dialog box, click the response curve menu
, and then choose Save Response Curve. (To later reapply the curve, choose Load Response Curve.)
If you originally created a 32-bit image during the Merge to HDR Pro process, you can later convert it to a 16- or 8-bit image.
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Adjust exposure and contrast to produce an image with the dynamic range you want. (See Options for 16- or 8-bit images.)
The dynamic range of HDR images exceeds the display capabilities of standard computer monitors. When you open an HDR image in Photoshop, it can look very dark or washed out. Photoshop lets you adjust the preview so that the monitor displays an HDR image whose highlights and shadows aren’t washed out or too dark. The preview settings are stored in the HDR image file (PSD, PSB, and TIFF only) and are applied whenever the file is opened in Photoshop. Preview adjustments don’t edit the HDR image file; all the HDR image information remains intact. Use the Exposure adjustment (Image > Adjustments > Exposure) to make exposure edits to the 32‑bpc HDR image.
Note:
To view 32‑bit readouts in the Info panel, click the Eyedropper icon in the Info panel and choose 32‑Bit from the pop‑up menu.
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Note:
You can also adjust the preview of an HDR image open in Photoshop by clicking the triangle in the status bar of the document window and choosing 32‑Bit Exposure from the pop‑up menu. Move the slider to set the white point for viewing the HDR image. Double-click the slider to return to the default exposure setting. Since the adjustment is made per view, you can have the same HDR image open in multiple windows, each with a different preview adjustment. Preview adjustments made with this method are not stored in the HDR image file.
The HDR Color Picker allows you to accurately view and select colors for use in 32‑bit HDR images. As in the regular Adobe Color Picker, you select a color by clicking a color field and adjusting the color slider. The Intensity slider allows you to adjust the brightness of a color to match the intensity of the colors in the HDR image you’re working with. A Preview area lets you view swatches of a selected color to see how it will display at different exposures and intensities.
A. Preview area B. Adjusted color C. Original color D. 32‑bit floating point values E. Intensity slider F. Picked color G. Color slider H. Color values
With a 32‑bpc image open, do one of the following:
In the toolbox, click the foreground or background color selection box.
In the Color panel, click the Set Foreground Coloror Set Background Color selection box.
The Color Picker is also available when features let you choose a color. For example, by clicking the color swatch in the options bar for some tools, or the eyedroppers in some color adjustment dialog boxes.
The lower part of the HDR Color Picker functions like the regular Color Picker does with 8‑ or 16‑bit images. Click in the color field to select a color and move the color slider to change hues, or use the HSB or RGB fields to enter numeric values for a particular color. In the color field, brightness increases as you move from bottom to top, and saturation increases as you move from left to right.
Use the Intensity slider to adjust the brightness of the color. The color value plus the intensity value are converted to 32‑bit floating point number values in your HDR document.
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Adjust the Intensity slider to boost or reduce the color’s brightness. The new color swatch in the Preview scale at the top of the Color Picker shows the effect of increasing or decreasing stops for the selected color.
The Intensity Stops correspond inversely to exposure setting stops. If you boost the Exposure setting of the HDR image two stops, reducing the Intensity stops by two will maintain the same color appearance as if the HDR image exposure and the color intensity were both set to 0.
If you know the exact 32‑bit RGB values for the color you want, you can enter them directly in the 32‑bit value RGB fields.
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Preview Stop Size
Sets the stop increments for each preview swatch. For example, a setting of 3 results in swatches of ‑9, ‑6, ‑3, +3, +6, +9. These swatches let you preview the appearance of your selected color at different exposure settings.
Relative to Document
Select to adjust the preview swatches to reflect the current exposure setting for the image. For example, if the document exposure is set higher, the new preview swatch will be lighter than the color selected in the Color Picker’s color field, to show the effect of the higher exposure on the selected color. If the current exposure is set to 0 (the default), checking or unchecking this option will not change the new swatch.
You can edit and add effects to HDR/32‑bpc images using any of the following Photoshop tools: Brush, Pencil, Pen, Shape, Clone Stamp, Pattern Stamp, Eraser, Gradient, Blur, Sharpen, Smudge, and History Brush. You can also use the Text tool to add 32‑bpc text layers to an HDR image.
When editing or painting on HDR images, you can preview your work at different exposure settings using either the 32‑Bit Exposure slider in the document info area or the 32‑Bit Preview Options dialog box (View > 32‑Bit Preview Options). The HDR Color Picker also lets you preview your selected foreground color at different intensity settings, to match different exposure settings in an HDR image.
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(Optional) Set the exposure for the image. See Adjust displayed dynamic range for 32-bit HDR images.
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For the Brush or Pencil tools, click the foreground color to open the HDR Color Picker and select a color. For the Text tool, click the color chip in the Text tool options bar to set the text color.
The Preview area of the HDR Color Picker helps you select and adjust a foreground color in relation to different exposure settings in the HDR image. See About the HDR Color Picker.
Note:
By default, the Toning Curve and Histogram limit and equalize your changes from point to point. To remove the limit and apply more extreme adjustments, select the Corner option after inserting a point on the curve. When you insert and move a second point, the curve becomes angular.
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