UPDATE: The good news is that Lightroom CC has addressed this issue. When I do a JPEG export now, it uses up nearly all CPU resources, so much so that my laptop gets a bit unresponsive (which is expected).
It all started with one of my customary tweet rants:
I was pointed to a great article written a couple of years ago that involved some great testing and tips for optimizing the JPEG output from Lightroom 2.x (thanks to @MarkusTyphoon for the tip). The main discovery is that Lightroom simply does not fully take advantage of multi-core and multi-threaded CPUs for JPEG exporting. This wasn’t news to me, but the detailed level of testing was impressive, as was the solution for a work-around: use simultaneous export processes.
I decided to replicate the tests on my own laptop; these files are ~25 MB Nikon D750 raw files being chewed on by an aging Core i7-2667 at 2.4 Ghz on battery power. Here’s what I discovered:
- Exporting 38 images as a single export batch took 529 seconds
- Exporting 38 images in three simultaneous batches (14 + 14 + 10 images) took 402 seconds
- I saw Lightroom CPU usage shoot up from the norm of bouncing between 45% and 85% to lock in around 90% to 98% and stay that high:
The net result? Exporting the images using multiple processes shaved 32% off the rendering time. That’s huge!
How to do this? Select your first image, then hold the shift key and click on an image 1/3rd of the way through your set. Press CONTROL+SHIFT+E to bring up the export window and start the first JPEG export. Repeat this process three more times with the remaining images, and you should see Lightroom processing three export jobs:
32% faster exports is a significant time saving, especially if you’re exporting a set with several hundred images (which pros do regularly). I’ll likely repeat these tests when I move to a 6-core system later this year (Haswell-E? Broadwell? Skylake? Too many choices!). With more physical cores, there may be an opportunity for more time savings if there are more than three export processes going on simultaneously.
Now if only Lightroom 6 would do something useful like take advantage of GPU acceleration and not feel so damn sluggish all the time…