I just stretched the limits of Lightroom’s Smart Previews this morning.
After editing the following image I decided to see what it looked like as a smart preview. I pushed the image quite a bit, exposing the colour in the sky as the sun set behind me in Lanzarote a few days ago.
The original image is dull and lacks contrast but with a little work I was able to expose the lovely shades of magenta and orange present. Here’s what it looked like when Lightroom was editing a DNG file:
But when I removed the file and Lightroom had to use the smart preview this is what that lovely colour gradient looked like:
There’s visible compression artefacts visible that aren’t in the original and it looks more pronounced in Lightroom. I didn’t push the image too much, but these sort of artefacts can be seen in Jpeg images of smooth colour gradients like a blue sky has. They’re really visible if you push the contrast at all, or modify the colours in the gradient like I did with this image.
Smart previews create images that are 2500px wide or tall which is a good compromise between full size RAW and not being able to edit the image at all, but on a high resolution screen like a Macbook Retina screen you won’t be able to zoom much.
I will continue to use smart previews. My 1TB+ photo archive can be crunched down to less than 200GB which is within the reach of a laptop, and still leave free space. Once I plug my external drive back in and fire up Lightroom I can then export the images and be sure that the final image is what I want.