You can bring out detail in both the sky and the horse
01 Start with the sky
Go to File>Open. Browse to horse.dng. Click Open to open it in Camera Raw. Press O to see clipping warnings. Set Exposure -0.65, Highlights -41, Whites -22, Clarity +11, Vibrance +42. With the Graduated Filter, draw from the top of the frame to the horse – set Exposure -70, Highlights -34.
02 Label the layer
Click Open Image. This takes the picture into the Photoshop editor. Go to File>Save As. Name it ‘composite’ and set the Format to Photoshop. Click Save. In the Layers panel, double-click on the locked Background layer’s thumbnail to unlock it. Label the layer ‘Sky layer’. Click OK.
03 Now for the horse!
Go to File>Open Recent. Open horse.dng. Undo the earlier changes: click Default, drag Clarity and Vibrance to 0, click the Graduated Filter icon, click Clear All. In the Basic panel, click the Zoom tool. Drag Exposure to +0.45. Set Shadows +52, Highlights -77, Whites -23, Clarity +24, Vibrance +44.
04 Remove chromatic aberration
Now that you’ve brightened up the horse, you’ll have revealed some colour fringing. Use the Zoom tool to magnify the image to 100% and drag with the Hand tool to see the fringes. Click the Lens Corrections panel, then click the Color tab. Click the Remove Chromatic Aberration box.
05 Add a mask
Click Open Image. Choose Select>All, Edit>Copy. Click the composite.psd tab. Pick Edit>Paste. You have a layer for the horse and one for the sky. Click the horse layer. Pick Layer>Layer Mask>Reveal All. A white mask appears. Click the Gradient tool. Press D. Click Linear gradient. Tick Reverse.
06 Combine the layers
Click in the top-left and draw a diagonal gradient down to the horizon. Thanks to the mask, you can see the horse from the top layer and the sky from the layer below. The angled gradient stops the sky from overlapping the horse. Pick File>Save to save the exposures as a layered PSD file.