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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.

Merging images of different exposures to create an HDR image

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 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 24bit 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 8bpc images.

· 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.

· 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 fstops 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.

Levels, Exposure, Hue/Saturation, Channel Mixer, Photo Filter.

Note:

Although the Exposure command can be used with 8 and 16bpc images, it is designed for making exposure adjustments to 32bpc HDR images.

Normal, Dissolve, Darken, Multiply, Lighten, Darker Color, Linear Dodge (Add), Lighter Color, Difference, Subtract, Divide, Hue, Saturation, Color, and Luminosity.

In the New dialog box, 32 bit is an option in the bit depth popup menu to the right of the Color Mode popup menu.

All commands including Fill, Stroke, Free Transform, and Transform.

Photoshop (PSD, PSB), Radiance (HDR), Portable Bit Map (PBM), OpenEXR, and TIFF.

Note:

Although Photoshop cannot save an HDR image in the LogLuv TIFF file format, it can open and read a LogLuv TIFF file.

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 Size, Canvas Size, Image Rotation, Crop, Trim, Duplicate, Apply Image, Calculations, and Variables.

Pixel Aspect Ratio (Custom Pixel Aspect Ratio, Delete Pixel Aspect Ratio, Reset Pixel Aspect Ratio, etc.)

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.

RGB Color, Grayscale, conversion to 8 Bits/Channel or 16 Bits/Channel.

Support for square and non-square documents.

Invert, Modify Border, Transform Selection, Save Selection and Load Selection.

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.

. (Bridge) Select the images you want to use and choose Tools > Photoshop > Merge To HDR Pro. Skip to step 5.

· In the Merge To HDR Pro dialog box, click Browse to select specific images, click Add Open Files, or choose Use > Folder. (To remove a particular item, select it in files list, and click Remove.)

· (Optional) Select Attempt To Automatically Align Source Images if you held the camera in your hands when you photographed the images.

· Click OK.

Note:

If images lack exposure metadata, enter values in the Manually Set EV dialog box.

A second Merge To HDR Pro dialog box displays thumbnails of the source images, and a preview of the merged result.

· To the upper right of the preview, choose a bit depth for the merged image.

Note:

Choose 32 Bit if you want the merged image to store the entire dynamic range of the HDR image. 8bit and (non-floating point) 16bit image files cannot store the entire range of luminance values in an HDR image.

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 > 32Bit 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

Choose one of the following tone-mapping methods:

Adjusts HDR tonality by adjusting local brightness regions throughout the image.

Radius specifies the size of the local brightness regions. Strength specifies how far apart two pixels’ tonal values must be before they’re no longer part of the same brightness region.

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.

Vibrance adjusts the intensity of subtle colors, while minimizing clipping of highly saturated colors. Saturation adjusts the intensity of all colors from –100 (monochrome) to +100 (double saturation).

Displays an adjustable curve over a histogram showing luminance values in the original, 32-bit HDR image. The red tick marks along the horizontal axis are in one EV (approximately one fstop) increments.

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.

Toning Curve and Histogram adjustment using the Corner option

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. 

Compresses the dynamic range of the HDR image while trying to preserve some contrast. No further adjustments are necessary; this method is automatic.

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.

Compresses the highlight values in the HDR image so they fall within the luminance values range of the 8 or 16bpc image file. No further adjustments are necessary; this method is automatic.

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: