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2017 iMac Pro: Zerene Stacker

2017 iMac Pro

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I use Zerene Stacker heavily for focus stacking and it takes minutes to do some stacks, so speed here matters a lot to me. Since I almost always stack with both PMAX and DMAP methods, this test totals the time of the two.

The gain from CPU cores is modest, the 2017 iMac 5K takes only 32% longer. Some code optimization is needed, since Helicon Focus is able to use all 18 cores quite well.

This stack uses 20 16-bit 45-megapixel images from the Nikon D850. See Nikon D850 'Focus Shift shooting' feature for Easy Focus Stacking.

Results below with macOS 10.13.3 including the Apple Supplementary Update. See the results from more systems with macOS 10.12.2 further below.

2017 iMac Pro 18-core vs 2017 iMac 5K: focus stacking in Zerene Stacker

Below—amazingly the 2017 iMac 5K with its four fast CPU cores is essentially the same speed as the 3.46 GHz 12-core 2010 Mac Pro and an 8-core 3.3 GHz 2013 Mac Pro. This is high praise indeed—1/3 or 1/2 the cores respectively—wow that 2017 iMac 5K represents incredible value.

The standout here in absolute terms is the 10-core 3.0 GHz iMac Pro. The 33% reduction in processing time means that a 4.5-minute stack becomes a 3-minute stack. Now that’s something I could grow to like. If only the iMac Pro were not actually slower than the iMac 5K for my other even more frequent workflow task.

There is a big fly in the ointment: not shown here is a far more important consideration, which I tested with the 2017 iMac 5K side-by-side with the 2017 iMac Pro 10-core: the iMac Pro visibly lagged the iMac 5K when retouching. Since I typically retouch at least 10 minutes and sometimes up to two hours, the initial stacking speed is a minor concern compared to interactive use, which is not at all as snappy as I’d like, even on the iMac 5K. But to have it visibly lag on the iMac Pro just screws the pooch.

Probably the 8-core iMac Pro would come in at round 220 seconds, which would be a 20% time reduction versus the 2017 iMac 5K. A 14 or 18 core iMac Pro would be very interesting for this particular application but how much faster things would go is hard to say, because memory bandwidth looks to already be limiting the 10 core iMac Pro.

The 2017 iMac 5K runs its fans heavily during this test at normal room temperature (75°F or so), whereas the fans of the iMac Pro are not even heard. The fans of the 2013 Mac Pro become audible but do not run heavily. My concern is that approaching 95°F, the 2017 iMac 5K will start to crap out, and lacking ECC memory might crash, whereas the iMac is both more robust in its cooling and has ECC memory, which should correct the bit errors I have seen when approaching the operating limits of all Mac (95°F).

The foregoing is not speculation, but based on actual experience running the 2013 Mac Pro and the 2015 MacBook Pro at around 95°F ambient—the Mac Pro showed ECC errors and the MacBook Pro reduced its clock speed to 0.8 GHz: see 2015 iMac 5K Runs at 0.8 GHz When Cold, Even with Warm Air Out Rear Vents and MacOS Bug: Kernel Task Uses Most or All CPU Cores Continuously (Ambient Temperature Too High).

This stack uses 20 16-bit 45-megapixel images from the Nikon D850. See Nikon D850 'Focus Shift shooting' feature for Easy Focus Stacking.

2017 iMac Pro vs others: Zerene Stacker
2017 iMac Pro
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