One of the advantages of digital photography is that you can shoot as many photos of the same subject as you like without worrying too much about composition or, in the case of action photography, of whether your subject was in focus all the time. This advantage is also a disadvantage: you risk stuffing your disk with useless images you’ll probably never going to use. How do you get rid of those duplicates and near-duplicates? Doing it manually is one possible cure, but it’s a lot better for your nerves if you do it with the help of an app. PhotoSweeper assists you when cleaning out your image database.
Working with PhotoSweeper can be incredibly simple: using the app, open your Aperture or Lightroom library and have it search for duplicates, or near-duplicates based on time interval or by comparing histograms or visual correspondence (pixels are alike). If you don’t use Lightroom or Aperture, you can just open folders or drag and drop images to PhotoSweeper. That is how I tested. I use the Photo Mechanic image browser (reviewed here), which keeps your images in the folders you define. When I offload a memory card, I ingest the RAW and JPEG image pairs to a folder and add pre-defined metadata using Photo Mechanic.
While testing PhotoSweeper with this setup, I was particularly interested in how it would treat these RAW/JPEG pairs. That proved to be as easy as advertised: there’s a Preference setting that allows you to compare only within the same image format. This means PhotoSweeper would compare JPEGs to JPEGs and RAW images to RAW. I had a collection of over 6,500 images to compare, and to see how PhotoSweeper behaved when it has to go through that many possible lookalikes, I processed them all at once. PhotoSweeper didn’t seem to mind. The program first creates a catalogue of all your images, internally creating small size bitmaps for later processing (you don’t get to see those; they serve only as representations of your images for easy comparison).
You can save that catalogue and come back to it later if you wish, which is great because the app will intelligently compare your images, but in the end you’ll need to decide whether you want to trash images or not — you have the last word. The cataloguing process went smoothly and didn’t take too much time. After cataloguing, you can first decide which algorithm you want to use. Duplicates only will find exact duplicates on a byte-per-byte basis. Other methods introduce some form of “fuzziness” as these resemble more or less the way you would yourself compare photos.
I decided to go with the default setting, which is Time + Bitmap — the interval between photos would be taken into account in addition to a visual likeness. I left all control sliders to their default settings as well. If you want to, you can change the bitmap size (at the cost of memory consumption), the interval, RGB sensitivity and other parameters to fine-tune the process. As it turned out, at least with my image collection, the default settings gave me excellent results. Once you’re happy with the way everything is et up, you press the Compare button.
My 6,500+ photos got compared in under 10 minutes (iMac mid-2011 i5/16GB). I found that quite impressive, certainly in view of the results. After comparing the photos, the app marks the images it thinks are duplicates or near-duplicates. You can then check images in the large thumbnail view (they’re grouped together in what PhotoSweeper thinks are series of lookalikes) and check them if necessary — or check the ones you think the app wrongly wants to keep.
PhotoSweeper managed to “understand” what “lookalike” means correctly about 95% of the time. The most consistent error the app made was that it wanted to keep JPEGs that weren’t paired with the proper RAW image. That error accounted for about 90% of the total mistakes it made. In my opinion, the app gave me an impressive, almost human result — I couldn’t have done a better job.
You can view images that are very much alike side-by-side in this part of the workflow, but in my case I was quite happy with the suggestions PhotoSweeper made. When you’ve gone through all the marked an unmarked images and have changed the ones that you weren’t happy with, all you need to do is click the Trash button to see all checked photos be thrown out the window.
In my case — with a lot of time lapse photos that I didn’t need anymore — there were some 2,000 images that I allowed PhotoSweeper to trash. That saved quite a bit of disk space, but above all it got rid of clutter. You can further fine-tune PhotoSweeper’s settings so you really get the most out of it, but even out-of-the-box I found it performing brilliantly. It’s ridiculously cheap at roughly €7.50 too.