A line like, “Grandma laughing when the candles went out,” is better than saying, “In this photo, Grandma is laughing at the candles out after the birthday party.” The photo book caption need not tell us everything the image already tells. Its role is to offer the reader the sliver of information the photograph itself does not provide, then get out of the way so that the picture stays front and center.
One way to try this out is to work it in to your early editing: pick one spread, write a one sentence caption for the photos, and then cut those one sentence captions down to their useful essentials: name, location, time period, or a bit of detail that adds some information that is otherwise lacking in the photo (or, at least, that changes your interpretation of the image). Words describing what we can see in the photo (standing, smiling, beautiful, laughing, playing, enjoying, having fun, etc.) don’t have to be stated in the caption unless that information is specific to the book or moment in question (for example, in a family photo book, it would be useful to state where the smile is coming from, and why it’s happening, even if it’s something so small that the viewer could just tell, “They look happy.”). This process quickly teaches you how to separate captions that enhance a page and caption that are competing with the photos.
In fact, crowded captions often are a red flag that the photos don’t belong in the book, that there needs to be a rethink on how to sequence the photos, or that some of the photos need to be paired better on the spread. Any single photo that requires three sentences of explanation just to make sense needs to go. It should not be the work of captions to explain what doesn’t belong on the page. A good caption is not there to save the reader, but to make something already obvious more specific.
The way a caption is presented on the page also needs to be just as considered as its words: if a caption is tucked against a photo it could look like an accident, but it it is close to the outside edge it could not be read properly in print. Give it space to breathe within your grid so that it looks like it has a place. Be careful where your captions are placed before ordering (check margins, safe zone, and gutter if you’re printing a book) in particular when placing captions on photos with a photo book, where small text can look very fine on screen but feel small in the printed product.
A travel guide will have different requirements than a photo memory book for what information its captions contain: A travel book might need place names (the name of a neighborhood or street, or perhaps a brief reference of moving through places A to B to C in the area or country), but a family book could use names or family relationships (or some brief phrases the family knows and will recognize in the future) to identify what’s happening. An event book could use some sort of sequential order (the preparation, the arrival, the ceremony, the dinner, the good-bye), but in a family book it wouldn’t be useful. These details, small as they are, help readers find a way to the page that helps them understand how it moves through a story and not just feels like a single moment from a diary.
One way to determine if this is true is to ask the question, “What does the caption add that the photo does not already tell?” If that question produces no answer, the caption doesn’t work, and should be shortened or cut altogether. If you have some kind of useful information in there (such as a name or location or date or some quiet little memory), then you know you’re writing to help the reader rather than help yourself as a photographer or designer, and you just give it enough room so that the text looks good on the page in its intended size. You know you’ve gotten the captions right, not by having a sentence under each photo, but by being able to flip through a two-page spread and understand how it reads as a visual story and still see what matters most: the photograph.