How to Stack: Stacking is a method of organization which helps you to bundle "like" images together. That being images which are extremely similar in content, part of a multiple shot series (example: HDR series, time lapse series or rapid fire series). The idea being if you have dozens of images that are nearly the same or need to be together to make sense, then why fill up your entire screen with them all. A single representative image will tell you all you need to know about the remaining "x" number of images.
To stack images you simply select all the images in a series or group which you wish to add. You do this by clicking on an image (hold ctrl pc /alt mac) to continue selecting multiple images. You can also select a large group of images in order by clicking the first images (hold shift) and then bookend the entire series by clicking again on the last image.
Once your images are highlighted, you can right click > stacking > group into stack. You'll now see all your images compress into a single image with an "x of y" box in the corner showing you the total number of images in the stack.
Stacking Automatically: So what if you've shot hundreds of photographs and every photograph is part of a series?
For example, maybe you were at drag race and as each car left the start line you would rapid fire 10+ images each time. Going in and manually stacking each car series one at a time is going to be a bit of a pain. So here's what you do.
Open your folder in "grid" view. Right click on any image > stacking > auto-stack by capture time. Here you'll see a slider which allows you to specify a period of time. Any images which are taken within that period of time will be stacked. In the above example you can assuming that any image within, let's say, 10 seconds is part of the same series of rapid fire shots of the same car. So we could set our time to ten seconds. Lightroom will automatically stack all images shot within ten seconds of one another into individual stacks. Easy peasy.
Ordering Your Stack: You may notice that when you group ("stack") images in Lightroom, it seems that the one photo which represents the stack most effectively, is never the first image in line. So what happens? Well, once you collapse your stack, you end up with an a "less than favorite" image being displayed as the stack thumbnail. Or maybe you wish to have all the images within the stack in specific order.
Option #1: Notice that when expanded, your stack images each have a number in the upper left corner representing their order within the stack (example: "2 of 7"). Simply click on the number box of the image you want to be in position #1. It will automatically move to position one allowing you to collapse the stack with your favorite image as the representative thumbnail. I'm not certain if this option occurs in LR 3 since I only noticed today while in LR 4.
Option #2: Additionally you can grab any image within an expanded stack and rearrange their order by clicking (to highlight) and dragging to a new locations within the stack. As such you can simply move any image via dragging to the #1 position. You will notice a black line between images as you move which designates where your drop location is.
Note: you can use this same technique to reorder images within any folder as well. Not just within stacks.
Option #3: If you rt-click on any images within your stack: Go to "stacking>move to top of stack".
Trackback from your site.