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How to Cull and Rate Photos for Capture One

By Ingo D ·

Photographers who use Capture One tend to know why. The colour rendering. The tethering. The session-based workflow that keeps every project self-contained. But there is one thing Capture One has never excelled at — and it is the same thing no RAW developer excels at: the first-pass cull of your photos.

You come back from a shoot with 1,200 frames. You open Capture One, create a new session, import the folder, and begin clicking through the browser at a frame a second. By the time you have picked the keepers, you have imported every single frame into your session — including the 1,100 you will never edit. Your session folder is bloated with previews and settings files you did not need. The cull has taken an hour, and the culling and rating pass is the slowest, least creative part of your Capture One workflow.

There is a faster order of operations: cull the shoot while it is still on your memory card, NAS, or working folder, before you ever create a Capture One session. When you do import, you bring in only the keepers — and those keepers arrive already rated, flagged, and colour-labelled. This article shows you the entire Capture One culling workflow, from first connection to final import.

Why is Capture One slow for the first-pass cull?

Capture One is a RAW processor and tethering tool built for colour-critical editing. Its browser can show thumbnails and lets you assign star ratings and colour tags, but it was never designed for fast, swipe-through triage of hundreds of frames. The browser requires you to click each thumbnail individually to view it at size. Preview generation on import takes time — several minutes for a folder of 1,000 RAW files. And most importantly, you have to import everything to see anything: which means your session folder fills up with proxy files, settings, and database entries for frames you plan to reject.

For a fashion photographer shooting 800 frames of a lookbook, or a portrait photographer with 400 headshot variants, the import-then-cull sequence adds a full hour before the first edit. That hour is pure overhead. It is not creative work. It is not billable time. It is the tax you pay for starting the cull at the wrong end of the workflow.

Can I rate and cull photos before importing into Capture One?

Yes — and it is the single biggest time-saver you can add to a Capture One workflow. You do the rating pass outside Capture One, on the device and in the moment that suits you, and let XMP sidecar files carry the decisions into your session automatically.

The key is XMP: the Extensible Metadata Platform, an open standard that Capture One reads natively, alongside Lightroom and Darktable. When you assign a 3-star rating to a RAW file, the rating is written to a small .xmp sidecar in the same folder. When you later open a Capture One session and point it at that folder, the rating appears without any import step, metadata merge, or manual sync. You go straight from rating to editing, with no duplicate handling in between.

How do XMP sidecars work with Capture One?

XMP sidecars are small text files with the .xmp extension stored alongside your RAW files. Capture One reads them on two occasions: when you import images into a session or catalogue, and when you manually reload metadata. If a sidecar exists for DSC_4521.NEF (i.e., DSC_4521.NEF.xmp), Capture One picks up any star rating, colour label, keyword, and pick/reject flag recorded inside it.

Capture One’s XMP handling differs from Lightroom in one important respect: Capture One prefers to store metadata internally in its own database after import, and it does not automatically re-read sidecars when you make external changes later. This means your pre-import cull must be complete before the session touches the files. The workflow is: cull and rate first, import second, and do not go back and forth. If you do need to re-rate externally after import, use the Metadata menu to reload, which we cover in the troubleshooting section below.

Setting up your Capture One culling workflow

You need a tool that reads your shoot folder directly — from a NAS, an SMB share, an external SSD, or a local folder — and writes XMP sidecars without creating a catalogue, importing files, or duplicating data. CullKit is built for exactly this.

CullKit is an independent product. It is not affiliated with or endorsed by Capture One A/S or Phase One A/S. It connects to NAS devices via standard SMB and writes standard XMP sidecars that any XMP-compliant editor reads.

The setup takes under a minute. If your photos are on a Synology NAS, enter the DiskStation IP (something like smb://192.168.1.50/photo) and connect. For QNAP, TrueNAS, or UGREEN, enter the SMB share path — smb://192.168.1.x/Multimedia on QNAP, smb://truenas.local/photos on TrueNAS, or the equivalent on your UGREEN NAS. For a local folder or external SSD, point at the directory directly. No import. No catalogue. Your files stay where they are, and the session you create later will reference them in place.

Step by step: cull your photos before you open Capture One

1. Connect to your shoot folder. After a job, your RAW files are in a folder on your NAS, external SSD, or local drive. Open CullKit, navigate to the folder. The grid shows your full shoot with responsive thumbnails. Pinch to zoom the grid density: many thumbnails for an overview, or few for closer inspection.

2. Run the first-pass cull. On iPhone and iPad, swipe right to keep a frame, swipe left to reject it. On Mac, use the keyboard: number keys for star ratings (1–5), P to pick, X to reject, arrow keys to navigate between frames. The interface is full-screen and purpose-built for fast binary decisions. With auto-advance enabled, the next frame loads immediately after each swipe or keystroke. A 1,200-frame shoot at 2 seconds per frame takes roughly 40 minutes.

3. Add star ratings and colour labels. After the first pass, take a second pass over the survivors — the 150 to 200 frames that survived the reject sweep. Assign 3-to-5-star ratings to the keepers worth editing. Apply colour labels — the standard palette Capture One shares with Lightroom: red, yellow, green, blue, purple — to group by subject, lighting setup, or delivery batch. A 200-frame second pass at 4 seconds per frame takes about 15 minutes.

4. Verify the XMP sidecars. Every rating, flag, and label you set is written to an .xmp file alongside each RAW on your storage. RAW+JPEG pairs share a single sidecar, following the Lightroom convention, so a dual-format shoot does not produce duplicates. You can confirm the sidecars exist by checking the folder in Finder or File Explorer: IMG_6721.CR3 should have IMG_6721.CR3.xmp alongside it.

5. Open Capture One. Create a new session or open your existing catalogue. Import only the keepers — skip the rejects. When Capture One reads the folder, the XMP sidecars are detected automatically. Your 4-star selects arrive pre-rated and colour-labelled, ready for the editing pass. You have skipped the import-everything bottleneck and gone straight from rating to editing.

Capture One Sessions vs Catalogues: does pre-culling work with both?

Yes, the XMP culling workflow works identically with both Session and Catalogue modes in Capture One. The only difference is in how you set up the import.

A Session is a self-contained project folder: all settings, previews, proxies, and trash files live inside one directory. This matches the pre-cull workflow particularly well, because you can point a session at a folder of pre-rated keepers and keep the session lightweight. Only the frames you intend to edit get session files. The rejects stay on your NAS or SSD, untouched, with no Capture One overhead created for them.

A Catalogue is a database that can span multiple folders and drives, more similar to a Lightroom catalogue. When you import into a catalogue, Capture One reads the XMP sidecars and stores the metadata internally. Again, the key rule is the same: do the cull first, then import. If you re-rate externally after import, use Metadata → Load Metadata (or right-click a folder and select Reload Metadata) to pull the changes back in.

What metadata transfers from CullKit to Capture One?

A complete rating pass in CullKit records four types of metadata, and all four travel into Capture One via XMP sidecars without any additional sync step:

  • Star ratings (1–5): Written to XMP and displayed in Capture One’s browser and viewer as the familiar five-star scale. Sort and filter by rating in the browser toolbar.
  • Colour labels: The red, yellow, green, blue, and purple palette Capture One uses for visual grouping. They appear as colour tags on thumbnails and are fully filterable in the browser Filters tool.
  • Pick and reject flags: Mapped as pick/reject decisions. In the Capture One import dialog, you can filter to show only picks, skipping every rejected frame before a single file is added to your session.
  • Keywords and tags: Dublin Core keywords written into the dc:subject field of the XMP sidecar. Searchable in Capture One’s Filters tool under the Keywords tab.

All of this metadata travels in the same .xmp file next to each RAW. The sidecar is the transport, and Capture One reads it without any intermediate translation.

How to import only your keepers into Capture One

Once your ratings are on disk as XMP sidecars, you can keep your Capture One session lean by importing only the frames worth editing:

  1. In Capture One, go to File → Import Images.
  2. Navigate to your shoot folder on your NAS, SSD, or local drive.
  3. In the import dialog, you will see every frame with its pre-assigned star rating already visible on the thumbnail — Capture One reads the XMP sidecars during the import preview.
  4. Use the Filter by Rating dropdown at the bottom of the import window to show only 3 stars and above, or only frames with a specific colour label.
  5. Select just those keepers and click Import. The rejected frames stay untouched on disk. Your session contains only the images worth editing.

If you have already imported everything before the cull — an existing session where you want to pull in late ratings — you can still benefit from the sidecars. Select the folder in the Library tool, go to Metadata → Load Metadata, and Capture One reads the XMP files alongside each RAW. Use the browser’s star-rating filter to hide the rejects and focus on your selects, even though they were imported earlier.

Troubleshooting: ratings not appearing in Capture One

  • Sidecars are not being read on import. Confirm the .xmp file shares the exact base filename of the RAW and sits in the same folder. For DSC_4521.NEF, the sidecar must be DSC_4521.NEF.xmp — not DSC_4521.xmp or DSC_4521.NEF.xmp.txt (a double extension added by some text editors).
  • Ratings disappeared after re-opening the session. Capture One stores metadata in its own database after the initial import and does not automatically re-read sidecars when files change externally. Use Metadata → Load Metadata on the affected folder to pull in the latest XMP values.
  • RAW and JPEG pairs show as duplicates in the browser. If you shot RAW+JPEG and Capture One shows two thumbnails for the same frame, check your preferences: under Capture One → Preferences → Image, ensure “Treat JPEG files next to RAW files as separate images” is unchecked. This lets Capture One pair them as one frame, matching the single-XMP-sidecar convention CullKit uses.
  • The connection to the NAS drops during the cull. Ensure your device is on the same network as the NAS. For large shoots (1,000+ frames), a wired or 5GHz Wi-Fi connection provides enough throughput for stable preview loading during the culling pass. CullKit auto-reconnects if the connection drops and preserves your session progress.
  • Capture One is slow to generate previews during import. This is normal for large RAW files. The advantage of pre-culling is that only the keepers need previews — you skip preview generation on the 80–90% of frames you rejected during the cull.

How is this different from culling inside Capture One or Photo Mechanic?

Capture One’s browser can assign star ratings and colour labels to photos, but only after import. You cannot cull from the import dialog itself, and every frame you view in the browser has already been added to your session, generating database entries and preview proxies. Photo Mechanic is the long-standing desktop culling tool of choice and writes the same XMP sidecars CullKit does — but it is a Mac and PC application that ties you to one machine.

CullKit’s value in a Capture One workflow is when and where the cull happens. You can cull on your iPad while your memory card copies to the NAS. You can cull on your iPhone on the train home. You can cull on your MacBook with keyboard shortcuts before creating a session. The output — standard XMP sidecars — is identical to what Photo Mechanic produces. The difference is that you are not chained to a single desk for the slowest, most repetitive part of your photography workflow.

Does this work with photos stored on a NAS?

Yes. CullKit connects to Synology Photos directly, or to any NAS over SMB — QNAP, TrueNAS, UGREEN, Asustor, and others — and writes XMP sidecars back to the same network location. Your Capture One session can reference the NAS folder as a source during import, reading the pre-written sidecars. For photographers whose entire library lives on a NAS, this means the culling pass stays local to the network, with no copy-to-laptop step required.

The privacy model is worth noting here because it matters to working photographers with client NDAs and confidential work: nothing is uploaded to a cloud during the cull. Your photos stay on your NAS or your local drive. Ratings are written directly to your own storage. There is no intermediary server, no third-party account, and no metadata stored outside your control. For more detail, see the privacy FAQ.

A note on what CullKit does not do

CullKit is a culling, rating, and organising app. It does not edit or develop photos. There are no exposure sliders, no colour grading, no crop tools, no layers. That work belongs in Capture One — and CullKit is designed to hand off cleanly to it. The job is to get you from a full memory card to a set of rated, colour-labelled selects as fast as possible, so your Capture One session starts at the editing pass, not the cull.

Try the Capture One culling workflow

CullKit is available on iPhone, iPad, and Mac. The free tier lets you browse any connected library — NAS, SMB share, external SSD, or local folder. The Pro tier (7-day free trial, then monthly or yearly) unlocks culling, star ratings, colour labels, tags, XMP sidecar writing, and folder organisation — everything you need for a pre-import rating pass that hands off cleanly to Capture One.

There is also a built-in demo mode with sample data, so you can try the full culling workflow before pointing it at your own photos.

Download CullKit on the App Store

CullKit is an independent product. It is not affiliated with or endorsed by Capture One A/S, Phase One A/S, Adobe (Lightroom), or Camera Bits (Photo Mechanic). Compatibility claims only.

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