How to combine images at different shutter speeds

You’ve probably heard about exposure blending, in which light and dark exposures of a scene are blended together, usually to balance land and sky. But how about shutter blending?

For this, rather than blending brightness, we’ll instead blend different-length exposures – one fast, one slow – to create a single image displaying both a split-second moment and a longer stretch of time.

In our first shot, the motion of the cyclist has been captured with a single off-camera flash. This required a fast shutter speed, so we used the camera’s maximum sync speed of 1/250 second – fast enough to capture the motion of the cyclist, but too quick to record much detail in the background.

For our second shot, we used a longer exposure of 15 seconds to capture more background detail and blur the motion of a passing gritter truck. (The interesting dashes of light are caused by the truck’s flashing beacons.) A tripod is essential when using shutter blending– both for the long exposure, and to make sure the two frames are in alignment.

Enter Photoshop

All we need to do now is combine the two frames together in Photoshop. We’ll start by making a few tweaks to the images in Camera Raw so that the tones and colours match, then bring them into Photoshop to do the shutter blending. This process involves a simple combination of layer masking and selection techniques.

This is all straightforward to master, and the technique involves skills that come in handy not just for shutter blending, but also for any kind of montage or composite image.

01 Improve the tones

Download our start files and follow along! Drag the two road_before.dng files into Photoshop. As they’re raw files, they’ll automatically open in Camera Raw. First, highlight the cyclist image in the filmstrip then go to the Basic panel on the right and set Exposure to +0.50, Contrast to +19, Highlights to -23, Shadows to +72 and Clarity to +31.

02 Open both images

Highlight the second image, then grab the White Balance tool from the Toolbar. Click on the road to correct the colours. Next, set Clarity to +38. Click the Select All button in the top-left, then hold Shift and click the bottom right Open Object button to open the images in Photoshop as Smart Objects.

03 Copy the layer

Go to the traffic trails image, then head to the Layers panel. Right-click the background layer and choose Duplicate Layer. In the Destination settings, choose Document: ‘road_before01 as Smart Object’ and click OK. Now we’ve copied the layer over, we don’t need this image any more, so we can close it down.

04 Align the layers

Our images aren’t properly aligned so we’ll need to fine-tune the position manually before we start shutter blending. Lower the layer opacity to 50%. Press Ctrl/Cmd+T for Free Transform, then drag and resize the box to match the two frames (or input X:4155.90px, Y: 2521.19px, W: 107.98%, H: 107.98%, Angle: 0.72°). 

05 Add a full mask

Press Enter to apply the transformation, then
bring the Opacity of the top layer back up to 100%. Drag the lower layer above the top one. Next, you need to hold Alt and click the Add Layer Mask icon in the Layers panel to add a full black mask that completely hides the top layer. 

06 Reveal the cyclist

Grab the Brush tool from the Tools panel and choose a soft-edged circular brush tip. Press D to set the colour to white, then paint over the area of the cyclist to reveal him. Don’t worry about being too precise at this point: just get a rough idea of which parts of the layer you want to be visible.

07 Check the mask

You need to continue painting with white over the foreground to reveal parts of the top layer. We’ve painted with white up to about the middle of the road. Hold Alt and click the Layer Mask thumbnail in the Layers panel to toggle a view of the mask to check where you’ve painted.

08 Blend the shadow

If you mistakenly paint over any areas you want to remain hidden, press X to switch the colour to black, then paint over parts of the layer to hide them behind the mask. The shadow of the bike is a little distracting, so press 3 for 30% brush opacity, then paint over the area with black to gradually hide it.

09 Select the figure

Highlight the image thumbnail on the top layer (rather than the mask), then grab the Quick Selection tool from the Tools panel. Paint over the head and body to make a selection. The tool will snap on to the edges of the figure as you paint. Use ] and [ to resize the brush tip.

10 Refine the selection

Continue painting to select the handlebars and the top part of the bike. Hold Alt and paint to subtract areas from the selection if the tool goes wrong. Next, click the Refine Edge button in the tool options. Set Radius to 1.9, Smooth to 7, and Shift Edge to -25. Change Output To to Selection and click OK.

11 Tidy the edges

Go to Select>Inverse to invert the selection. Now any painting will be restricted to the area outside the cyclist. Highlight the Mask Thumbnail on the top layer. Grab the Brush tool and set colour to black, then paint to hide the layer and tidy the edges around the cyclist.

12 Tidy the mask

Press Ctrl/Cmd+D to deselect, then zoom in close to the handlebars. Paint precisely with white and black to reveal the bike frame, handles and wires and paint black to hide the gaps where the background is visible. Press X to quickly switch between black and white.

13 Add a grad

The bottom-right corner looks a little too bright, so we’ll re-edit the layer in Camera Raw. Double-click the cyclist layer thumbnail to send the image back into Camera Raw. Grab the Graduated Filter tool from the Tools panel and drag inwards from the right corner. Set Exposure to -1.65, then click OK.

14 Desaturate the road

The road from the traffic trails layer looks too yellow compared to the cyclist layer, so double-click the thumbnail on road_before02 to send the image back to Camera Raw. Grab the Adjustment Brush and paint over the road, then set Saturation to -44, Exposure to -0.20 and Clarity to +15. Click OK.

15 Make a new layer

Hold Alt and click the Create New Layer icon in the Layers panel to access the New Layer options. Name the layer ‘Dodge Burn’ then set the blending mode to Overlay and tick ‘Fill with Overlay-neutral colour’. Click OK, then grab the Brush tool. Set the colour to black and press 1 for 10% brush opacity.

16 Dodge and burn

Paint with black on the Dodge Burn layer to darken parts of the image, such as the corners, the face, clothes and any uneven parts of the road. Press X to switch to white and paint to lighten areas, like the background on the right and the highlights on the face.

17 Adjust the colours

Click the Create Adjustment Layer icon and choose Levels. Set Channel to Blue, then drag the two output sliders at the bottom inwards so that they read 7 and 240. Next, select the Red Channel, then drag the midpoint slider to 0.85 and the white point slider to 240.

18 Sharpen and Crop

Press Ctrl/Cmd+Shift+Alt+E to merge a new layer, then right-click it and choose Convert to Smart Object. Next, go to Filter>Other>High Pass. Set Radius to 2px and click OK. Go to the blending mode drop-down at the top of the Layers panel and choose Overlay. Grab the Crop tool and crop in slightly tighter.