This technique combines simple shooting and editing techniques to make an image that you couldn’t create with just a camera alone. By shooting and blending two or more photos, taken using the right exposure settings, we can make a picture that mixes both fast and slow shutter speed effects, giving a wonderful sense of energy and movement.
How it’s done
All you need to do is take two or more photos from the same position; one at a fast shutter speed and the other at a slow shutter speed, then combine them in Photoshop. But there are some important things to remember. First, the camera must be in the same position, with the same framing, in both shots. It must also be focused in the same place and use the same aperture settings. Second, you need the right kind of subject; something with predictable movement.
The subjects that work
Trains, trams and fairground rides are perfect subjects to try this technique out on, because they stick to predictable paths, moving through the frame in the same place, over and over. In the example images I found a bridge over a mainline railway, with express trains coming past every few minutes, so it was easy to get the shots required.
Time of day is also important. You need the light to be bright enough to make a fast shutter speed possible, but not so bright that you can’t set a slow shutter speed for the motion blurred image. Therefore early or late in the day work well.
1/ Find the right spot
A spot overlooking busy railway tracks, or tram lines is a good place to try out this technique.
Find a location where you can set up a tripod and will be able to wait for a while between shots, without needing to move the camera. You don’t want to be disturbed as there’s nothing as annoying as getting the first shot you need, then realising you have to move. Therefore a quiet spot away from lots of people is best. Here, I used a footbridge over the railway, leaving plenty of space for anyone to move past me if required.
2/ Set up on a tripod and compose
Using a tripod or similar support is vital, as you need to make sure there's no camera movement between shots.
Next, take time to refine your composition. Again, you don’t want to take the first picture, then find that you don’t like the framing, or you’ll need to start all over again. Work out where the sharp subject will be coming through the frame, and try placing that on one of the thirds, so there’s a nice balance. Once you’re happy, lock the camera’s position, focus where you want expect the subject to be, then switch to manual focus, so you don’t need to set it again.
3/ Take the slow shot
For the first shot, set a slow shutter speed, so that there's lots of motion blur visible in the subject.
Set the camera to aperture-priority mode and dial in an aperture of somewhere between f/8 and f/11. Now set the ISO to a low level. I set ISO 100. Next, check the shutter speed. You need a speed that’s slow enough to blur the movement of the subject, but this will depend on how fast it’s moving. For the trains in the example, 1/2sec was plenty, so I started shooting as they came past. However, if you’re not getting a slow enough speed, try setting a lower ISO, or close the aperture a little.
4/ Take the fast shot
For the fast shot, you need a higher shutter speed, so that the subject is kept sharp. Increasing ISO helps with this.
After you’ve got some motion-blurred pics, you can take the sharp shot. Without moving the camera, or changing the point at which it’s focused, increase the ISO, to a point where the shutter speed is fast enough to keep the subject acceptably sharp. Again, the speed required depends on how fast it’s moving. Here, I settled on a speed of 1/320sec at an ISO of 6400. I would’ve liked faster, but didn’t want to push the ISO much higher, to avoid digital noise. Time this second shot, so the subject is in the part of the frame where you focused.
5/ Keep shooting if required
Shooting more blurred versions helps you fill up the frame when it comes to blending them in Photoshop.
Although the effect is possible with just a single fast and a single slow shot. You may want to repeat steps 3 and 4. Both to make sure you have the subject sharp, and also to give you more blurred trains in the frame. In the example image, I waited until trains had come past on all of the tracks in the view, so I could use the blurred look across the whole frame.
6/ Load the pictures into Layers
The separate images must be loaded into layers, so that they can be blended. You can do this in an automated way, or cut and paste them one on top of the other.
Open the images you want to use into Photoshop, then go to File > Scripts > Load Files into Stack. Click Add Open Files, and tick Attempt to Automatically Align Source Images (this will correct any minor movements between frames, for instance from vibrations from the trains). Hit OK, and the pictures will be loaded into a new, layered document. Go to Window > Layers to see them all stacked up. Now, in the layers palette, click and drag the fast shot with the sharp subject to the top of the stack.
7/ Blend the exposures
By using Layer Masks you can set which parts of the different pictures are visible. Here, white is painted into a black mask so that only a small amount of the sharp image shows over the blurred one below.
Add more masks as you work down the layer stack, bringing in the blurred parts exactly where you want them.
Click on the top-most layer, and go to Layer > Layer Mask > Hide All. In the Layers palette, a black mask will appear next to the layer. Next pick the Brush tool, and in the Options bar, make sure you’re using a soft edge and 100% Opacity. Set it to paint white (press D), then paint over the picture to bring back a little of the sharp subject. Reduce the Opacity to around 20% and paint again to soften the join. Now click on the Layer below add another Hide All mask, and paint in the blurred elements you want. Repeat until you’ve masked all but the lowest layer. Finally, go to Layer > Flatten Image and File > Save.
Take it further
Blending the exposures isn’t the end of the story. Like any image, you should then improve the contrast and colour to show it off at its best. In the final picture, I also used the Crop tool to angle the composition, give it a more dynamic finish.
After blending, keep working on the image, to bring out the best in it.
. digitalrev.com2017-5-17 03:00