Set up Lightroom Classic for culling speed

Most Lightroom slowness during a first pass is not the processor. It is Lightroom being asked to draw a picture it has not drawn yet. This is the one time setup pass that fixes that: preview type at import, three numbers in Catalog Settings, the Performance tab, and where the catalog sits. Every path checked against Adobe's own documentation.

The setting matters more than the machine

First, which app. This is about Lightroom Classic, the desktop catalog program with the Library and Develop modules. It is not about Lightroom, the cloud based app that shares the name. Adobe ships both, they are genuinely different programs, and Lightroom does not give you preview build choices at import because it manages its own storage. If your left panel says Catalog, Folders and Collections, you are in Classic and this all applies.

Here is the part that takes people too long to accept. When Lightroom Classic drags during a first pass, the processor is usually not the bottleneck. You are pressing the right arrow onto a frame with no preview built at the size you are viewing, so the program stops and renders one. Half a second of that, across 2,000 to 4,000 wedding frames, is most of an evening spent watching a spinner.

So the fix is not a faster computer. It is deciding once, in advance, what Lightroom Classic should draw and when. That is about fifteen minutes of settings across two dialogs, and it holds for every job afterward. If you want the symptom by symptom version, read why Lightroom feels slow when you are culling. This is the setup you do before the next card goes into the reader.

Get the import dialog right and half of it is gone

The single highest payoff setting lives in the Import window, in the File Handling panel on the right, under Build Previews. Adobe documents four choices in its import options guide, and the one you pick decides whether the waiting happens while you are making coffee or while you are trying to work.

The practical routine that suits most working photographers: import with Embedded & Sidecar, do the fast pass on flags, then build 1:1 previews only for the shortlist that survived. You are not paying to render 3,000 full resolution previews when 800 of them are what you will actually look at closely.

One honest caveat. With Embedded & Sidecar you are looking at the camera's rendering, not Lightroom's, so the image can shift slightly when Lightroom later builds its own preview. For deciding whether someone blinked, that does not matter. For a final color judgment, it does.

Three numbers in Catalog Settings

Open Edit > Catalog Settings on Windows, or Lightroom Classic > Catalog Settings on macOS. The preview options are on the Previews tab in current releases, and on the File Handling tab in older ones. Three values matter.

Standard Preview Size. Adobe's advice is to choose a size equal to or larger than your screen resolution, and it gives the worked example of a 1920 by 1200 pixel screen, where you would choose 2048 pixels. Set it smaller than your screen and Lightroom has to render again the moment you go full screen. Set it far larger and you are building pixels you never see.

Preview Quality. Adobe's own performance guide recommends Low or Medium, because it keeps the preview files small. The scale works like JPEG quality. On a first pass, where the question is eyes open or eyes shut, Medium is plenty.

Automatically Discard 1:1 Previews. Adobe recommends Never or After 30 Days, so the expensive previews stick around. The catch is disk space, and it is not small. Those previews live in a file called [Catalogname] Previews.lrdata next to your catalog, and across a busy season it grows into tens of gigabytes. Thirty days is the sensible middle: long enough to cover a delivery cycle, short enough that last spring is not still parked on your drive.

The Performance tab: GPU and cache

Open Edit > Preferences on Windows or Lightroom Classic > Preferences on macOS, then the Performance tab.

Use Graphics Processor

Adobe's GPU documentation lists three options. Auto lets Lightroom decide the right level of support for your hardware, and it is the default. Custom lets you switch on Use GPU for Display, Use GPU for Image Processing and Use GPU for Export individually. Off turns acceleration off entirely.

Leave it on Auto unless you have a reason. The reason worth knowing: the GPU does far more for Develop than for scrolling a grid of thumbnails, and on some hardware and driver combinations it causes redraw glitches. If your Library module stutters or tears while everything else is fine, set it to Off for one session as a test. Adobe also asks you to keep the graphics driver up to date, which is the least glamorous and most frequently correct advice in the whole document.

Camera Raw Cache

This is where Lightroom keeps partly processed image data so it does not redo the same work. Adobe states the default is 5 GB, and notes some users find increasing it to 20 GB or more can dramatically speed up performance. Point it at your fastest drive. If you have the space, this is free and takes ten seconds.

The same tab has Generate previews in parallel, which builds several previews at once rather than one after another. On a modern multi core machine, switch it on before a big import and go and eat something.

The catalog, the previews, and the drive underneath them

This is the part people get wrong when they buy a big external drive and put everything on it.

Adobe is unambiguous: catalog files cannot be stored on network drives, although your photos can be. And storing the catalog, the image files and the previews on a solid state drive improves performance. The practical arrangement for most photographers is the catalog and its previews file on the internal SSD, always, and the RAW files wherever there is room.

Be deliberate about that split. The catalog and previews are what Lightroom touches thousands of times an hour during a pass, while the originals only get read when you zoom in or export. Fast disk for the thing that gets hammered, capacity for the thing that gets read occasionally. If your files are scattered in a way that makes this hard to sort out, fix that first with a folder structure you can live with.

Adobe recommends running Lightroom Classic on machines with 12 GB of RAM or more. And when things slow down over a season, run File > Optimize Catalog, which tidies the catalog's internal structure. It takes a few minutes and it is the closest thing Lightroom has to a tune up.

Two things worth switching off while you pick

Pause syncing. Adobe's performance guide suggests you temporarily pause Sync With Lightroom while you import and edit on the desktop. Uploading in the background while you are trying to move through 3,000 frames is a fight over the same disk and the same network, and you will lose it.

Automatically Write Changes Into XMP. In Catalog Settings, on the Metadata tab, Adobe's guide recommends deselecting this for performance. Every flag and rating you set otherwise triggers a sidecar file write, and during a fast pass you are setting hundreds of them a minute.

Be honest with yourself about the trade off before you switch it off, though. XMP sidecars are how your flags and ratings travel to other software. If you hand files to a retoucher, or move selections between applications, that data needs to exist on disk and not only inside the catalog. The workable compromise is to leave it off during the pass, then select everything and use Metadata > Save Metadata to File once you are finished. We go through what survives that journey and what quietly does not in moving selections between tools.

Smart previews, and one warning

Smart previews are the fourth lever, and the one with a catch. They are small proxy files, based on the lossy DNG format, that let you work when the drive holding your originals is not connected. Adobe's own example is stark: 500 raw files taking 14 GB on disk produced smart previews totaling 400 MB.

For a first pass on a laptop with the originals sitting on a drive at home, that is genuinely transformative. But there is a trade off you have to hold onto, and it is the reason this deserves its own article. A smart preview is a smaller file. Judging critical focus from one can mislead you, because you are not looking at all the pixels the camera recorded. Adobe now shows a warning dialog at startup if the Preferences option called Use Smart Previews instead of Originals for image editing is switched on, which tells you how seriously they take it.

Use them for the pass where you are judging expression, eyes and duplicates. Reconnect the drive before you make final calls about sharpness. The full version of this, including how to build and discard them and exactly which judgments are safe, is in smart previews for culling.

What none of this actually fixes

Set all of this up and Lightroom Classic stops making you wait. That is worth the fifteen minutes. But be clear about what you just bought: you made the road faster, not shorter.

You still look at every frame and make every keep or pass call yourself. Lightroom has no built in way to spot a blurred frame or a closed eye, so every technical check is your eyes doing it, one photo at a time, including on the eleven near identical frames from one burst. A UK survey of more than 300 wedding photographers, reported by PetaPixel, put culling at 11 percent of working time against 4 percent spent actually shooting. Faster previews do not move that ratio much, because the time is going into judgment, not rendering. Pairing this setup with the keyboard shortcuts worth learning gets you closer, since it takes your hands out of the equation too.

Where we sit, stated plainly: Kepla is building an app that does the technical first pass for you and hands you a shortlist, so you open Lightroom with roughly 800 candidates from a 2,000 frame wedding rather than the whole card. It marks its picks and nothing else. No file is ever deleted, moved or renamed, and every frame it did not pick is one tap away. That app is still being built for iPhone, iPad and Mac. The part of Kepla that works today is the booking page, which is live and free while we build, and it is the only piece we will claim is finished.

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