Page updated: 21 July 2026
Lightroom vs Photoshop: Why Photoshop Files Get So Big
Every photographer eventually notices it: Lightroom edits barely add anything to your storage, while Photoshop files can explode in size. I’ve seen PSDs reach hundreds of megabytes from what look like simple edits. So I decided to run a clear, real‑world test using three images with identical visual results — one edited in Lightroom, one in Photoshop.
The goal was simple: find out exactly why Photoshop files grow so much, and how Lightroom keeps things so small.. Here's the article, comparing Lightroom and Photoshop filesizes after editing 3 different images, with similar looking results.
Lightroom vs Photoshop Editing File Size
The Three Test Images
I used three images that represent everyday editing:
- Image 1: basic global adjustments
- Image 2: medium‑complexity masking
- Image 3: heavier local edits with multiple masks
All three were edited to look visually identical in Lightroom and Photoshop. The only difference was the software used — not the result.
The Results: Lightroom vs Photoshop File Size
The difference was dramatic.
Lightroom: added around 0.5–1 MB of data per image, even with multiple masks.
Photoshop: added tens or hundreds of megabytes. The largest PSD reached 834 MB — twenty‑three times the size of the original RAW.
This wasn’t a one‑off. Every Photoshop version grew significantly, while Lightroom barely changed the file size at all.
Why Lightroom Files Stay Small
Lightroom uses a non‑destructive, instruction‑based editing model. It doesn’t change the pixels in your RAW file. Instead, it saves tiny text instructions that tell Lightroom how to render the image.
Even complex masks add very little. Lightroom stores AI segmentation data in lightweight sidecar files, usually totalling less than 1 MB.
In short: Lightroom stores instructions, not pixels.
Why Photoshop Files Grow So Quickly
Photoshop works completely differently. Every adjustment layer, mask, Smart Object, and pixel edit becomes part of the PSD. Masks are full‑resolution grayscale images. Layers store pixel data. Smart Objects store entire embedded files.
It’s powerful — but it comes at a cost.
Photoshop stores pixels, not instructions.
That’s why even simple edits can produce a 100–300 MB PSD, and why more complex edits can balloon into hundreds of megabytes.
What This Means for Your Workflow
If you work on a lot of images, Photoshop’s file sizes add up quickly. Large PSDs take longer to save, longer to open, and require far more storage and backup space.
Lightroom, on the other hand, keeps everything lightweight. You can edit hundreds of images without worrying about storage or performance.
Lightroom’s Workflow Advantage
Lightroom also makes exporting easier. I use Export Presets for different sizes, formats, sharpening levels, and destinations. One click and the job is done.
Photoshop can do the same, but it requires more steps — and beginners often find Actions difficult to set up.
The Bottom Line
This comparison made one thing very clear: Lightroom is far more space‑efficient than Photoshop.
Both programs have their strengths, but if you want to keep your storage footprint low while retaining full editing flexibility, Lightroom’s instruction‑based workflow is the better choice for everyday editing.
I’ve written a full technical breakdown explaining exactly how Lightroom and Photoshop store edits — including XMP, ACR, layers, masks, and segmentation maps. You can read it here:
