How did we ever manage without stacks? For those who don’t know, cataloguing programs like Aperture, Lightroom and others can group related images together and display them as a single thumbnail image or expand the stack so that all the images in the stack are visible. This has many different uses. You can keep bracketed exposures together, for example, group similar images from a photo shoot or, in the example I’m going to demonstrate, use the Aperture auto stack feature to group together images taken in a continuous burst mode.

My pictures come from an afternoon spent shooting at a local motor racing circuit. I was testing a new camera at the time (the Canon EOS 40D) and in particular its 6fps continuous shooting mode. In all, I ended up with some 338 individual images – but since many of the cars looked similar, and in some instances I was waiting for the same cars to come round again, there was no quick and easy way of separating them and grouping them into individual sequences.

It’s easy enough to create stacks manually in Aperture, but this job still looked pretty tedious. Which is why I turned to Aperture’s auto stack option instead.

This is rather clever. It uses the exact time the photograph was taken, which is embedded in all digital camera images, to work out the interval between shots. If the interval is shorter than a certain time, it stacks them together.

01 The Auto-Stack command

Aperture auto stack

First, you’ll need to select all the images you want to auto-stack. I’ve created a new album for my motor racing shots, then used the command-A shortcut to select them all. The Auto-Stack command is on the Stacks menu…

02 Stacking intervals

Aperture auto stack

The Auto-Stack panel has just one slider (1), which controls the interval between shots. The idea is that you pick an interval that matches the gap between your shots (you might think) or maybe the duration of the sequence (which seems more like how it works). In any event, if I set an interval of 1, Aperture automatically stacks all the shots in each sequence (2)… nearly. In fact, there are some leftover shots like this one (3) at the end of some sequences.

03 Changing the interval

Aperture auto stack

To fix this, I’m increasing the interval to 2, and that seems to fix the stacking perfectly. This is what you need to do with this tool – find the perfect interval to stack the right shots without including any spurious ones. It’s a lot simpler than it sounds, because you usually leave a much longer gap between sequences and keeping them separate is not usually an issue.