Modern computers can run most operations in Photoshop very fast.  But there’s one step that’s always slow: saving files.  I did a head to head comparison of the various options that are most relevant for luminosity masking to see what’s best.  Exact times were recorded by Photoshop (if you haven’t seen it, the area at the bottom that normally lists your file size can be changed to “timing” if you click the > sign).  And all test data listed here was measured on the new 2016 MacBook Pro (which ironically is slower than the 2014 MacBook Pro, as I discuss below).

I tested TIF, PSD, and PSB files – as these are the relevant options for saving layered files.  I prefer TIF because you can save 4GB files and see them in Lightroom.  PSD is also a very common choice (but the 2GB size limit is frequently an issue when I’m blending exposures).  I avoid using PSB because it cannot be previewed in Lightroom at this time, but it has the distinct advantage of allowing you to save images with no practical size limit.

• TIF (NONE image compression / RLE layer compression)  =>  1.52GB file in 3.3 – 3.5s.
• TIF (NONE image compression / ZIP layer compression)  =>  641MB file in 50s. 
• TIF (ZIP image compression / RLE layer compression)  => 1.49GB  file in 13.2s.
• TIF (ZIP image compression / RLE layer compression)  =>  612MB file in 59.4s.
• PSD => 641MB file in 50s
• PSB => 641MB file in 50s

 

From this, we can conclude:

• Uncompressed TIF is the fastest option by far (20X faster than a fully compressed TIF), but the files are 2.3X larger.  If you care more about speed than small files, this is definitely your best best.  You could also use this on your working file, and then save over the file with compression when you are done.
• TIF with NONE/ZIP offers similarly files nearly the smallest possible size, but faster.  This is generally my preferred option.  (PSD and PSB are exactly the same this way, but TIFF offers the ability to save the largest files that may be previewed in Lightroom).
• Hard disk speed is not very important if you are saving compressed files.  The compressed files takes nearly 20x longer to save, even though they are more than twice as large (that’s >40x the time to save each MB of data).  The difference is the time required for the CPU to run the compression algorithm.  Granted, a solid-state drive (SSD) will still show a benefit over a slow spinning hard drive, but I wouldn’t worry about how fast that SSD is for this purpose.  And as I note below, a faster hard drive is no guarantee of faster files saves from Photoshop.

If you’re use uncompressed TIFs for speed, you should be aware of an issue that you may eventually run into.  Photoshop’s predicted file size (at the bottom of Photoshop) for this file was 842MB.  This is only an estimate, as it hasn’t yet run compression.  As you can see in the actual file sizes above, dramatically underestimates the true space needed to save an uncompressed TIF.  The is important because you might see an estimate that makes it appear that your file is safely within the 4GB TIF limit, when it is not (and then you’d get a 4TB file size error when you try to save).  If you run into this, just save again with compression enabled.  Or save as a PSB.

 

The 2016 MacBook Pro is slower than the 2014?  Yep, at least for saving files from Photoshop.

I also did some head to head testing of my 2016 MacBook Pro with 2TB SSD vs my 2014 MacBook Pro with 1TB SSD.  The newer drive is dramatically faster, testing at 2-3X faster with the BlackMagic Disk Speed Test.  But given how Photoshop can save the uncompressed 1.5GB file in 3 seconds, disk speed is not the limiting factor.  Compression requires a lot of CPU calculations.  What I can’t quite figure out yet is why the new 2016 2.9GHz i7 is actually significantly slower than the 2014 2.8GHz i7 I tested.  The 2016 Macbook Pro actually takes 8 seconds longer than the 2014 to save the same PSD file.  I suspect that part of this is because the 2014 can temporarily boost its CPU to 4.0GHz, while the 2016 can only boost to 3.8GHz (though there are of course other differences between these different generations of i7 processors). But that’s only a 5% difference, and I’m seeing a 16% difference in save times.  I can’t fully explain the poor performance of the new laptop.  As expected, when saving files with minimal compression (TIF with no/RLE), the new machine is faster (at 3.5 vs 4.4 seconds).

Speed really depends on what you’re doing.  The Surface Blur filter is about 10% faster in my testing on the newer machine.  Exporting a video from Final Cut Pro is dramatically faster on the new machine (36% faster in my testing).  In general, copying files is much faster on the newer machine, as disk speed is the bottleneck there (as opposed to CPU when trying to compress a file while saving it).

 

Other options to speed up Photoshop:

If you want to see more tips to how to speed up Photoshop, please see the article I wrote on optimal settings.

You can move a significant amount of file size to a linked PSB via Lumenzia. This gives you a much faster way to save documents if you have a bunch of base layers you won’t change much (such as a panorama, focus stack, or an exposure blend).