Stacking Images to Make Long Exposure
I am not a fan of pictures with water in them where the water isn’t smooth. I prefer the look of a smooth river, ocean, lake or any body of water. However, this isn’t always easy to do. It requires the right conditions and setup. In cases like that there is a way you can essentially fake the long exposure to get the water smooth. This can be done by taking multiple images and stacking them in Photoshop. Using layers and smart objects you will take all of your stacked images; Photoshop will then compare each image to the previous image adding pixels where they did not exist. With the water moving per image Photoshop is adding those missing pixels to each image giving the look of a long exposure.
This is done basically in 3 Parts
Shooting
Editing the photos
Stacking in Photoshop
I’ll go through each one here quickly
Shooting: This is key, you need to plan your shot. This technique works best for large bodies of water and / or clouds. Your foreground / background play a huge factor in this. It can not be busy with trees, grass, people… or anything else that moves. If those other things are moving Photoshop will try to add it to each shot but they will be a blur and look bad. The images I have posted below are perfect for this technique. The only thing here moving is the water (and if there were clouds). You must shoot all shots at the same shutter speed/exposure/ISO and from a Tripod or solid surface without moving the camera. The amount of photos you take is entirely up to you and how much of the effect you want. The more you take, the more of a long exposure look you get. Keep in mind though, that you also have to edit all of these. A good rule of thumb is take as many as you want to simulate the long exposure. For example if you want a 1 sec long exposure look and shooting at 1/50th of a second, 50 shots would give you that 1 sec. (This is not an exact science, more of a ‘close enough’)
Editing the photos: You can edit all of these photos in Lightroom and be sure to synchronize them. I won’t go through those steps here, but you can find out how in my full Lightroom Training course. This blog is more about how to do the technique of simulating the long exposure.
Stacking in Photoshop: With all of the photos selected in Lightroom. Right Click > Edit In > Open as Layers in Photoshop. This could take a while depending on your computer and how many photos you have taken. If you shot correctly and from a tripod they should mostly be lined up. However, I still prefer to do the extra step to align them. Be sure to select all layers in layers panel then go to Edit > Auto Align Layers. I will choose the default here of Auto. Now that all of the layers are lined up, you need to convert them to a Smart Object. This is easy to do, with all of the layers still selected right click in layers > Convert to Smart Object. This will then merge all of your layers in to one Smart layer. Now the magic, with that smart object selected go to Layers > Smart Objects > Stack Mode > Mean. Then wait. It might take a while for Photoshop to go through each image. Once done you can then continue with your edits on your newly created “long exposure” photos.
Here is the before and after shot of one I have done. I took only 25 images at 1/160th and you can see how great the effect is. Imagine now taking 100+ shots and getting a really smoothed out water
