The Milford Track walk (more information) is 4 nights/ 5 days and about 54 kilometres. There are waterfalls everywhere you look – the region gets about 12 meters of rain a year! I didn’t want to carry a tripod as well as the rest of the gear required. So how to photograph water falls without a tripod and still get that smooth water look? And I couldn’t use an ND filter to get a slow shutter speed, obviously that would require a tripod.The statistics function in Photoshop was the answer. The basic steps are:
- take a burst of images at a ‘normal’ exposure – i.e. expose and freeze the water. I’ve used as few as 5 but this image used 24;
- Hand-hold carefully during the burst keeping the focus point steady on a section of the image. The X-t1 does 8 frames a second;
- Stack the images in Photoshop using the statistics (mean) function so that anything moving between each image will blur in the final stacked image. Anything static will be sharp.
Problems. What problems?
Each image is about 33MB. So that’s 24 of them open in Photoshop at once (the actual steps are below) – about 800MB. The final stacked image is about 1.32GB. I expected to have to composite at least one of the 1/800s images and mask in leaves and branches and such that might have moved between shots and would blur when I don’t want them too.
Here’s one of the images that comprised the stack:
I use Lightroom (LR) as my RAW processor. You don’t need precisely 24 images that’s just how many I had. Using fewer will still give a good result and probably be less processor intensive.
- With the images catalogued in LR I first make some global adjustments such as white balance, set the white point and black point and anything else, but don’t crop. Sync theses adjustments across all 24 images. It isn’t necessary to do this first step but I like too.
- With all 24 images selected in LR, right mouse click and edit in Photoshop. Each image will open in its own window in Photoshop.
- From the menu in Photoshop, one the images have all opened, select File->Scripts->Statistics.
- In the dialogue box select “add open files”. Make sure “attempt to automatically align source images” is checked and the “stack mode” is “mean”.
- Click OK…wait awhile.
- Once it finishes you’ll be presented with a stacked image that has the water (or anything that moved) blurred much as a slow shutter speed would render it.
- You can close the 24 images now and save the stacked image. Save the stacked image as a tif file rather than a PSD file otherwise if it’s greater than 2GB you’ll need to save it as a PSB file (Photoshop’s large image file format) and LR won’t display a thumbnail for that file type. You will still get a message about some tif viewers not being able to render large files but just click OK as LR is able to cope with large tif files.
- Open one of the 24 images and move it so it’s a layer over the stacked image. I select the whole image (Ctrl+A), hold down the shift key and use the move tool to move the image to the stacked image. Mask out any blurred parts of the stacked image that you want to be sharp.
- Save the image and make any adjustment in LR (or photoshop before closing if that’s your preference)
Before closing it experiment with the other stack modes to see what they do. From the Layer menu; Layer->Smart Objects->Stack Mode and select another one.
Adobe offers the following about image stacks and the statistics options: Adobe help