When you save a JPEG it’s easy to just accept your default image options, click File > Save and get on with your next task. But that probably means you’ll always be using the same JPEG compression level, and unless you’ve tuned this to an optimum figure, your final images could be anything up to ten times larger than they need to be.

Could this be a problem for you? The open source Caesium provides an easy way to find out. Point the program at a selection of images (PNG, BMP and WMF are supported, as well as JPG) or an entire folder, and it can quickly recompress them all with a lower quality setting, before reporting on any savings it’s achieved.

This is generally fairly easy to set up. Images can be imported with a click or two; a slider allows you to set a new compression level, and you can opt to save the recompressed images into the same folder or a new one.

A Preview window helps ensure that your recompressed images still look great

Caesium also includes an optional image resize tool to cut the file size even further, handy when you want to share your latest photos with others, but you know they don’t need the original high resolution versions.

How does it perform? JPEG results were generally very good, with typical savings ranging from 30 to 90% (and without any significant reduction in visual quality), although around 10% of our images remained virtually the same size, or got larger.

PNG compression was relatively poor, though, with most of our test images increasing in size. (While this is disappointing, it doesn’t actually cause any problems, as you can tell the program not to save recompressed images if they’re larger than the original.)

There’s no way to say precisely what sort of results you’ll get from Caesium, then – it all depends on your source images. If you just want to shrink some large JPEG photos, though, there’s a good chance that you’ll see a significant reduction in file sizes. And as it’ll take at most ten minutes to find out, we’d recommend you download a copy, see what the program can do for you.