How to Create a Photo Mosaic in Lightroom & Photoshop

How to Create a Photo Mosaic in Lightroom & Photoshop: Complete Guide

A photo mosaic — a large image built out of hundreds of smaller tiled photos — is a striking way to bring together a big collection of images, whether that’s yearbook photos, employee headshots, or years of family photos. This guide covers both halves of the process: building the mosaic itself from a folder of source photos using Lightroom and Photoshop’s Contact Sheet automation, then taking it further by turning that mosaic into a repeatable pattern and overlaying it on a photo so the final image looks like it’s made entirely out of hundreds of smaller pictures.

Every photo used in this walkthrough, including the full 300-photo mosaic source set, is available as a free Download, so the exact same files used here can be followed along with step by step.

Planning a Good Mosaic Source Set

Before importing anything, it’s worth thinking about what the source photo collection actually represents, since a mosaic is only as compelling as the photos that make it up. A folder of genuinely varied images, different subjects, different colors, different compositions, produces a much richer, more visually interesting mosaic than a folder full of near-duplicate shots, since variety is what gives individual tiles enough contrast against their neighbors to read clearly once the grid comes together. The 300-photo set used in this example was specifically chosen to represent a wide range of people and scenes, which pays off directly once the mosaic is assembled and later blended into a portrait.

Importing Source Photos into Lightroom

Start in Lightroom with a folder of source images meant to become mosaic tiles (this example uses 300 different photos). Simply click and drag the entire folder into Lightroom, which brings up the import dialog — clicking Add and then Import brings every photo into the catalog in just a couple of seconds.

Cropping Every Photo to a Square

Since mosaic tiles need to be uniform, every source photo needs a square crop. Select one image and press R to open the Crop tool, choose a 1:1 aspect ratio, and position the crop as desired before pressing Enter.

Syncing the Crop Across All Photos at Once

Rather than repeating that crop manually on every photo, go back to the grid view, select all photos with Ctrl/Cmd+A, and use Sync Settings. Click “Check None” first to clear every option, then check only Crop before clicking Synchronize. This applies the exact same square crop to every photo in the batch in one step.

Fixing Individual Crop Placement

Because the synced crop applies the same relative position to every photo, some images will end up cropped in an awkward spot — cutting off a face instead of centering it, for example. Pressing R on any individual photo reopens its crop for a quick manual fix, including repositioning or rescaling it, then pressing Enter to confirm. Working through the filmstrip and re-pressing R on any photo that needs adjustment makes it easy to catch and fix every awkward crop before moving on.

This is worth doing methodically rather than spot-checking a few images at random, since even a handful of badly cropped tiles will stand out once they’re part of a finished mosaic. Working through the filmstrip in order and re-cropping anything that looks off, one photo at a time, is a simple but effective way to make sure every single tile in the final mosaic is well composed before moving on to export.

Exporting All Photos at a Small Size

With every photo cropped to a square, select all of them again and go to File > Export. Under Image Sizing, resize the long edge down to 150 pixels — since these will become tiny individual tiles in a mosaic, they don’t need to be large. Set the file format to JPEG, sRGB, with a quality of around 80, and set Export To to Choose folder later. Click Export, then in the file window create a new folder named 150px, click Create and then Open, and Lightroom exports all 300 photos into it.

Why a Uniform Tile Size Matters

Exporting every photo at exactly 150 pixels on the long edge, after they’ve all already been cropped to the same square aspect ratio, is what makes the next automated step possible. If tile sizes varied even slightly, Photoshop’s Contact Sheet automation would have no consistent grid to build against, and the resulting mosaic would have gaps, overlaps, or uneven spacing between tiles. Getting the sizing and cropping consistent up front in Lightroom, across all 300 photos at once, is what turns the next step from a manual nightmare into a single automated action.

Building the Mosaic with Contact Sheet II

From here, the rest of the process is automated inside Photoshop. Go to File > Automate > Contact Sheet II. Choose the exported 150px folder as the source images, then set the document size based on the math of the tile grid: since each tile is 150 pixels square, 20 columns wide comes out to 3000 pixels, and 15 rows tall comes out to 2250 pixels. Set the thumbnail placement to 20 columns and 15 rows, and uncheck “Use Filename as Caption” since captions aren’t needed on the finished mosaic.

Letting Contact Sheet II Assemble the Grid Automatically

Clicking OK lets Photoshop calculate the layout and place every one of the 300 photos into a perfectly even mosaic grid automatically, with no manual placement required. At this point, anyone who only wants a standalone photo mosaic already has a finished result — the remaining steps take it further by turning that mosaic into a texture that can be applied to any other photo.

It’s worth pausing here to zoom into the finished grid and confirm every tile landed where it should, since Contact Sheet II’s automatic placement is reliable but still worth a quick visual check before moving on to the next stage, especially on a large 300-image grid where a single misplaced or corrupted file could otherwise go unnoticed.

Turning the Mosaic into a Reusable Pattern

To use the mosaic as an overlay, define it as a Photoshop pattern: go to Edit > Define Pattern, give it a name like “Photo Mosaic,” and confirm. This stores the entire mosaic inside Photoshop’s pattern library, ready to be applied to any image going forward.

Applying the Mosaic as a Pattern Fill Layer

Open a different sample photo — a portrait in this example — that the mosaic pattern will be applied to. Add the pattern as a new fill layer through Layer > New Fill Layer > Pattern. The saved mosaic pattern loads in automatically and tiles infinitely across the layer, with a Scale control that determines how many repetitions of the mosaic show up across the image.

Blending the Pattern with Soft Light

Change the pattern fill layer’s blend mode from Normal to Soft Light, which lets the underlying photo’s tones and shapes show through the mosaic tiles rather than sitting flatly on top of the image. Once applied, the mosaic immediately starts to look like it’s forming the actual photo, since the pattern layer picks up the brightness and contours of the portrait underneath it.

Fine-Tuning Pattern Scale and Contrast

Double-clicking the pattern fill layer reopens its settings, where the Scale slider controls how large or small each individual tile appears: a lower scale packs in more, smaller tiles, while a higher scale shows fewer, larger tiles. Since every photo has a different amount of fine detail, there’s no single correct scale — around 40 percent worked well for this particular portrait, but each new image benefits from testing a few different scale values to find what reads best.

Reducing Contrast with a Clipped Levels Layer

If the pattern layer’s contrast feels too strong, add a Levels adjustment layer clipped specifically to the pattern fill layer. Bringing the black and white Output Levels sliders in a little softens the overall contrast of the pattern, making the underlying photo easier to see through the mosaic tiles, and since it’s a separate adjustment layer, it can be toggled on or off at any time.

Clipping the Levels layer specifically to the pattern fill layer, rather than letting it affect the whole image, matters here: an unclipped adjustment would also change the contrast of the underlying portrait itself, undoing some of the careful exposure and color work that photo already had. By restricting the adjustment to just the pattern, the mosaic tiles can be softened independently while the base photo underneath stays exactly as it was, which keeps the overall effect controllable and reversible at every stage of the process.

Working with Your Own Photo Collection

While this example uses a curated 300-photo stock set, the entire workflow applies just as well to a personal photo collection — a year’s worth of phone photos, every picture from a company retreat, or a family archive going back years. The main variable to adjust for a personal collection is simply the total photo count: fewer source photos means a smaller contact sheet grid (fewer columns and rows in the Contact Sheet II dialog), while a much larger collection can be arranged into a bigger, more detailed grid. The underlying steps, cropping to a square, exporting small, and letting Contact Sheet II handle placement, stay exactly the same regardless of how many photos are involved.

Ideas for Using a Finished Photo Mosaic

A finished photo mosaic effect has plenty of practical uses beyond a standalone image: wedding or event photographers can build a mosaic from every photo taken at an event and layer it over the couple’s main portrait as a client keepsake, giving them something far more memorable than a typical printed gallery. The same effect works well as a website background, a social media banner, or a “best of the year” roundup image built from a collection of favorite shots pulled from an entire year of photography. Because the underlying pattern is fully reusable, a single mosaic built once from a meaningful set of photos can be applied across several different final images, letting the same story be told in more than one format without redoing any of the setup work.

Why This Technique Works

Splitting this workflow between Lightroom and Photoshop plays to each app’s strengths: Lightroom’s batch Sync Settings makes cropping and exporting hundreds of photos to a uniform size fast, rather than repeating those steps by hand on every image, while Photoshop’s Contact Sheet II automation handles the tedious math and placement of arranging every tile into a perfectly even grid — math that would be genuinely painful to work out and place manually across 300 individual images. Turning that finished grid into a Photoshop pattern, rather than treating it as a one-off flattened image, is what makes it reusable across any future photo, since a pattern lives inside Photoshop’s library and tiles infinitely at any scale, rather than being tied to the exact dimensions of the document it was created in. And Soft Light blend mode is the specific ingredient that makes the overlay believable: it lets the underlying photo’s actual brightness and shape show through the pattern, so the mosaic reads as if it’s forming the image rather than sitting as a flat, unrelated grid on top of it, the way Normal blend mode would if applied directly instead.

Final Thoughts

Once the source photos are cropped and exported and the mosaic pattern is saved inside Photoshop, that same pattern can be reused on any number of future photos, adjusting only the scale and Levels contrast to fit each new image. The two-stage process, batch preparation in Lightroom followed by pattern-based automation in Photoshop, turns what could be an enormous manual task into something that comes together in only a few clicks per photo.

Quick Reference: Keys, Menus and Settings

• Square cropR, Aspect 1 x 1, Enter
• Sync the cropCmd/Ctrl + A, Sync Settings, Check None, Crop, Synchronize
• Export the tilesFile > Export: Long Edge 150 pixels, JPEG, sRGB, quality about 80, Choose folder later
• Build the gridFile > Automate > Contact Sheet II: 3000 x 2250 pixels, 20 columns, 15 rows, captions off
• Make a patternEdit > Define Pattern
• Overlay itLayer > New Fill Layer > Pattern, blend mode Soft Light, Scale about 40%
• Less contrastLevels clipped to the pattern fill, Output Levels brought in a little