iMac Pro first impressions

10-core w/ Vega64.  Upgrading from a 2014 Retina iMac.

Relatively briefly, and in no particular order:

  • I don’t see why the very slightly different colour scheme, vs the regular iMacs, is such a big deal to some people.  Yes, it’s fairly obviously a different colour.  No, it doesn’t really look any better (nor worse) than the regular iMac’s colour.
  • It’s disappointing that it comes with such crappy input devices (the mouse & keyboard at least).  They’re the usual ergonomic & general usability disasters that Apple’s infamous for as of recent years.
    Digression:  I also recently got a new MacBook Pro 13″ with Touch Bar for my work machine, which has an even worse keyboard than the iMac Pro, if such a thing is possible.  It’s literally painful to type on.
  • According to Intel’s Power Gadget tool, it basically sits at 3.6 GHz permanently.
    On the upside, it doesn’t seem to ever drop below that, despite nominally having a 3.0 GHz base frequency, even under the heaviest loads I can throw at it (including heavy, concurrent GPU use).
    On the downside, it’s supposed to turbo up to 4.5 GHz, but I’ve never seen the tool report that.  It does get up above 4.0 GHz if you only have one or two threads actually active, but only barely.  Intel’s tool only has 20ms sampling resolution, so it’s quite possible it is bursting to 4.5 GHz in very short stints.  In fairness, the regular iMacs exhibit basically the same behaviour – my 2014 Retina iMac nominally boosted up to 4.4 GHz, but in reality rarely if ever hit that.  Under load, that iMac struggled to reach 4.0 GHz.  Unless the ambient temperature was uncomfortably cold, it’d easily fall down to not much more than 3.0 GHz under any kind of sustained load, and sometimes even further, into the 2.x GHz range.
  • The fan is quite audible under any real load, even though I have some loud Thunderbolt disk bays and other things even closer to me than the iMac Pro.  I have no idea what some reviewers have been talking about w.r.t. the fan being “whisper quiet” or outright “inaudible”, because it definitely is not quiet.  It’s not loud, to be sure, but you can’t miss it.
    Under basically no load, there is indeed very little fan noise, but that’s both an unrealistic use case and certainly no better than the regular iMacs.
  • It does feel dramatically faster than a non-Pro iMac.  I did not expect this.  Certainly I expected significant objective improvements in parallel workloads – mainly batch photo & video editing in my case – but in fact the speed improvement is very noticeable even in single-threaded workloads.  I’m not sure why yet… the internal SSD is faster than the SATA SSD in my prior iMac, but the difference I’m seeing doesn’t seem plausibly explained by that [alone].
    I’m also seemingly seeing it perform significantly better under load, w.r.t. user interaction.  Even with all CPU cores completely busy, and the GPU likewise, interactive use remains basically as fast as when it’s idle.  This is a pretty big difference – and very pleasant improvement – over the non-Pro iMacs.  It’s really nice to not have to just walk away while CPU-intensive tasks are running.
  • The screen doesn’t immediately appear much different – in terms of colours, contrast, brightness, etc – to my old 2014 Retina iMac.  But it’s very clear which is which, because the iMac Pro has no image retention issues, whereas the 2014 iMac has pretty severe ones.
    Though when specifically looking at sRGB vs Display-P3 examples, the difference is quite a bit moreso than I expected, which is of course a pleasant discovery.
  • It’s so much better to have a proper, native VESA mount vs the hacks you had to do with prior iMacs.
  • iStat Menus can’t read any sensors (except CPU frequency, once Intel’s Power Gadget is installed), though I expect this is going to be fixed fairly soon, in a future version.
  • The ports on the back aren’t properly aligned with the case where they protrude, unlike non-Pro iMacs.  Meaning when you plug a cable in, it doesn’t align relatively flatly against the curved case, but rather tilts upwards a bit.  This is a really odd change – though obviously minor and practically insignificant.
  • I don’t yet understand why, but Lightroom Classic CC is noticeably snappier.    Particularly in the Develop module as you make edits and then wait for the results to appear on screen.  In some cases it’s an order of magnitude faster – e.g. less than a second instead of 5-10 seconds.  It’s still not consistently fast by any means, but it’s no longer always infuriatingly slow.
    I’m unconvinced, regardless, that the laws of physics will allow creation of a computer upon which Adobe’s software won’t run agonisingly slowly.
  • Officially it’s quite a bit heavier than the non-Pro iMacs, but I was surprised to find that it’s actually lighter for me… though that’s because with the stand removed – replaced by the VESA mount – it of course under-weighs the regular iMacs with their fixed stands still stuck in them plus a VESA mount adapter.

ProPhoto RGB vs JPEGs

Most common photo editors – e.g. Lightroom – let you choose the colour gamut to use for exported photos.  In Lightroom (at time of writing in January 2018) you have a fairly short list, of today’s common options – sRGB, Display P3, Adobe RGB, and ProPhoto RGB.  Since we’re all obsessive nerds, that we’re given an option dictates that we must make an explicit choice.  More pragmatically, the default in Lightroom – and many other photo editors – is sRGB, which is the one option that’s definitively wrong, so in this case you really do have to change it to something else, if you care about image quality at all.

So, what should you choose?  Well, obviously you want your exported photos to maintain as much of the colour gamut they contain as possible, and as accurately as possible – as part of the general principle that you want it to be the highest quality and as close to what you see on your screen as possible.  Modern digital cameras are capable of capturing far more than the sRGB space, and modern displays are also capable of larger gamuts too (typically Adobe RGB or Display P3, at time of writing, if not the union of both).  Thus why sRGB is unequivocally the wrong option (and any purported counter-arguments about colour calibration issues in web browsers and so forth are moot, because all decent web browsers handle colour management correctly & intuitively, and anyone not using one of those browsers clearly doesn’t care about a lot of things, least of all colour accuracy).

So then it’s just a question of which colour space is bigger, right?  That’s easy – ProPhoto RGB is huge.  A complete superset of all the others.  It actually encompasses colours that don’t even exist as far as the average human is concerned, because they’re outside our visual range.  So just use that, right?

Yes.  Maybe.  It depends.

The thing is, if you increase the colour gamut you encode your image in, you reduce the precision of your colours, all other things being equal.  Because you’re taking e.g. 8 bits, so 256 possible values, and spreading them out over a wider spectrum.  Thus each “bucket” – digitally quantised colour – is going to be bigger, coarser, and have a wider margin of error.  What this can mean in practice is visible banding in images which “should” be higher quality, because they have a much bigger colour gamut!

Larger colour gamuts really need correspondingly larger bit depths, in order to avoid sacrificing colour accuracy (or in plain terms, to avoid visible banding or posterisation).

Thus, if you’re exporting as ye ol’ JPEGs (an image format that’s just not very good, though it’s had a good run at over twenty-five years old at this point) where you’re stuck with 8 bits per pixel, it’s probably a bad idea to use ProPhoto RGB.  It’s too likely that in practice you’ll see nasty banding.  Instead, you’re probably better off striking a compromise and choosing either Display P3 or Adobe RGB, which aren’t so much bigger than sRGB that banding is often more visible, but are fully representable on many contemporary displays.  In theory as displays get better – i.e. wider gamuts – you’d want to upgrade, but in reality JPEG should be long dead before we get the next significant jump in real-world display gamuts, and their successor format(s) will undoubtably support much higher bit depths, eliminating this trade-off.

On the other hand, if you’re already exporting in modern formats – e.g. HEIF – where 10-bit (or better) bit depths are supported, you can consider extra large gamuts like ProPhoto RGB (just make sure you then use greater bit depths, as HEIF also supports 8-bit channels, and some software will still default to that).  It becomes more of a question of your target audience, your expectations for the longevity of that particular rendering of the photo, etc.

And if you’re using 16-bit colour depths, such as are options for TIFFs or other typical intermediary formats (e.g. when going from Lightroom to Photoshop, or vice-versa), then ProPhoto RGB is the best option, because there are no practical downsides.  Today ProPhoto RGB probably far exceeds the colour gamut your camera(s) can actually capture, but that’s okay – your camera(s) can probably capture more than just Adobe RGB or Display P3 too, and with 16 bits per pixel you’ve got plenty of colour resolution, so why sacrifice your camera’s capabilities?


This still leaves the choice of Display P3 vs Adobe RGB, for your typical web (etc) exports.  I’ve been using Adobe RGB myself for a long time, since that was basically the next step up in displays for the longest time.  However, since Apple has delivered Display P3 to the world, Display P3 almost overnight became far more commonly supported in the real world.  Remember that any modern iPhone, iPad, or iMac supports Display P3, and most quality standalone PC monitors do also.  There’s also an argument to be made that it is a more practical expansion on sRGB, since it increases not just your greens but also your reds:

sRGB vs AdobeRGB vs DCI-P3
(image courtesy of Smeterlink on Stackexchange)

iMac Pro benchmarks & performance evaluations

Bare Feats – 8-core versus 10-core iMac Pro: The Final Conflict (8-core, 10-core)

  • After Effects – BenchTest Render
  • Blender – BMW CPU Render
  • Blender – Pavillon CPU Render
  • Compressor – BruceX to HEVC
  • Final Cut Pro X – BruceX 5K Export
  • Geekbench – Single-core & Multi-core CPU
  • Photoshop – Noise Reduction
  • Premiere Pro – Export for Blu-ray
  • Premiere Pro – Blur Render

Ars Technica – iMac Pro review: Expensive, hard to upgrade, but holy Jony Ive it’s fast (10-core, Vega64)

  • Cinebench R15 CPU
  • Geekbench 4 CPU Single-core & Multi-core
    • Native & in Windows 10 running in Parallels
  • Geekbench 4 GPU Compute (Metal & OpenCL)
  • GFXBench Metal Offscreen (1080p) – T-Rex, Manhattan, & Manhattan 3.1
  • Quickbench Storage Test, Extended Test Average
  • World of Warcraft: Legion FPS
  • Xcode WordPress iOS app compile

Craig A. Hunter – iMac Pro 18-core Follow Up Review (18-core, 10-core)

  • AVX-512 Vector Add Benchmark Parallel Performance
  • LINPACK Shared Memory Benchmark Using Intel MKL
  • USM3D NACA 0012 Airfoil Parallel Performance

9to5Mac – First 18-Core iMac benchmarks showcase obvious multi-core benefits (8-core, 10-core, 18-core)

  • AJA System Test (SSD Performance)
  • Final Cut Pro X 4K ProRes Export from 8K RED RAW (12:1)
  • Geekbench 4

Bare Feats – What if the iMac Pro had THREE Vega GPUs? (8-core, Vega64)

  • LuxMark GPU LuxBall
  • LuxMark GPU Hotel
  • Blender Pavillon Barcelona
  • DaVinci Resolve Play/Render 3NR nodes

AppleInsider – iMac Pro vs 2013 Mac Pro (Part 4) – 3D rendering and thermals (8-core, Vega56)

  • After Effects CC ProRes 422 Render
  • Blender BMW CPU
  • Blender BMW GPU
  • Maya 2018 Model Village Render

AppleInsider – iMac Pro vs 2013 Mac Pro (Part 3) – video editing (8-core, Vega56)

  • Final Cut Pro X BruceX
  • Final Cut Pro X 1080p Render & Encode
  • Final Cut Pro X 4K H.265 Encode
  • Final Cut Pro X 4K Render
  • Final Cut Pro X 4K Render & H.264 Encode
  • Final Cut Pro X 4x4K Render & H.264 Encode
  • Final Cut Pro X 4K Stabilisation
  • Final Cut Pro X 8K Render & ProRes Encode
  • Premiere Pro 1080p Render & H.264 Encode
  • Premiere Pro 4K H.265 Encode
  • Premiere Pro 4K Render & H.264 Encode
  • Premiere Pro 4x4K Render & H.264 Encode
  • Premiere Pro 4K Stabilisation
  • Premiere Pro 8K Render & H.265 Encode

DPReview – Speed Test: iMac Pro vs Alienware PC, Mac Pro and MacBook Pro (8-core, Vega64)

  • After Effects RAM Preview
  • Photoshop Radial Filter
  • Premiere Pro 4K Render

AppleInsider – Apple’s iMac Pro vs 2013 Mac Pro (Part 2) – photo editing comparison (8-core, Vega56)

  • Lightroom Classic CC
    • Convert 50 RAWs to DNGs
    • Export 50 JPEGs
    • Generate 50 1:1 Previews
    • Import 52 42MP RAWs
  • Photoshop CC
    • 9 Shot HDR Merge
    • Noise Reduction
    • Open 9 RAWs

Bare Feats – iMac Pro Has A Thunderbolt 3 Storage Surprise For You (8-core)

  • AJA System Test – 16G Sequential Read
  • AJA System Test – 16G Sequential Write

Macworld – iMac Pro review: Mac Pro power in the shape of an iMac (8-core, Vega56)

  • Forecast MP3 Encode
  • Geekbench Compute GPU
  • Geekbench Single-core & Multi-core CPU
  • Handbrake 1080p H.264 Encode
  • iZotope De-Echo
  • iZotope Spectral Denoise B
  • Logic Bounce
  • Unigine Valley (High)

Cinema5D – iMac Pro Review – Is It Worth the Money? (10-core, Vega64)

  • Final Cut Pro X H.264 HD 25p Export
  • Final Cut Pro X ProRes 422 4K 25p Export
  • REDCINE-X PRO 6K ProRes 4444 Export

AppleInsider – Apple’s iMac Pro vs 2013 Mac Pro with benchmarks and specs (8-core, Vega56)

  • Cinebench R15 CPU
  • Geekbench 4 OpenCL
  • Geekbench 4 Single-core & Multi-core CPU
  • Unigine Heaven

Bare Feats – What if the iMac Pro had TWO Vega GPUs? (8-core, Vega64)

  • Blender – BMW CPU Scene
  • DaVinci Resolve – Play/Render Noise
  • DaVinci Resolve – Play 5K RED Clip
  • LuxMark – GPU LuxBall
  • LuxMark – GPU Hotel

DigitalArts – Apple iMac Pro review – this superbly designed workstation is most powerful Mac ever (10-core, Vega64)

  • Cinebench R15 Render & Real-time 3D
  • After Effects CC 2018 Render

Bare Feats – 8-core and 10-core iMac Pros Running Pro Apps (Part Two) (8-core & 10-core, Vega64)

  • Motion – Render RAM Preview
  • Compressor – BruceX HEVC 10-bit Transcode
  • Logic Pro X – Maximum Tracks
  • Blender – Render BMW Scene CPU-only & GPU-only
  • DaVinci Resolve – Transcode 5K RED clip to ProRes 4444 XQ

Mac Performance Guide – 2017 iMac Pro (8-core & 10-core, Vega56 & Vega64)

DigitalFilms – Putting Apple’s iMac Pro Through the Paces (10-core, Vega64)

  • Adobe Media Encoder 1080p ProRes to 4K H.264 Transcode
  • Adobe Media Encoder OpenCL ProRes Render
  • After Effects ProRes Render
  • Compressor 1080p ProRes to 4K H.264 Transcode
  • Final Cut Pro X BruceX Render & Export
  • Final Cut Pro X Playback
  • Final Cut Pro X Render & ProRes Export
  • Premiere Pro Playback w/ Single & Multi-layer sequences

Bare Feats – Low End iMac Pro Running Pro Apps (8-core & 10-core, Vega64)

  • After Effects CC Render
  • Compressor Export
  • Final Cut Pro X Export
  • Lightroom Classic CC JPEG Export
  • Photoshop CC Noise Reduction
  • Premier Pro CC Export

Bare Feats – Low End iMac Pro Running Games versus Other Macs (8-core Vega64)

  • DIRT Rally 2560×1440 Average FPS
  • Tomb Raider 2560×1440 High FPS
  • Total War: Warhammer 2560×1440 High FPS
  • Tomb Raider 2560×1440 High FPS

Bare Feats – Low End iMac Pro versus two Mac Pros and one iMac 5K (8-core & 10-core, Vega64)

  • DaVinci Resolve 14 Noise Reduction
  • Cinebench Multi-Core CPU
  • Geekbench Metal Single GPU
  • Geekbench Multi-Core CPU
  • Geekbench OpenCL Single GPU
  • LuxMark GPU LuxBall
  • LuxMark Multi-Core CPU

Bare Feats – iMac Pro with Pro Vega 56 GPU
versus optional Pro Vega 64
(8-core, Vega56 & Vega64)

  • Cinebench OpenGL
  • Compressor Transcode (BruceX to Apple 4K)
  • Final Cut Pro X Export (BruceX to ProRes 4444 XQ)
  • Geekbench 4 Metal GPU Compute
  • Geekbench 4 OpenCL GPU Compute

Bare Feats – iMac Pro PCIe-based Flash Storage: How Fast Versus Other Macs?

  • AJA System Test 15G Sequential Reads & Writes – Testing the Apple Pro Video Apps on the New iMac Pro (10-core, Vega64)

  • Compressor 4.4.0 H.264 & MXF Export (from ProRes 422)
  • Final Cut Pro X 10.4.0 4K Export to ProRes 422, H.264, & MXF
  • Final Cut Pro X 10.4.0 BruceX XML Test
  • Final Cut Pro X 10.4.0 Import Clips
  • Final Cut Pro X 10.4.0 Multicam Playback & Render
  • Final Cut Pro X 10.4.0 ‘Real World’ H.264 Export
  • Final Cut Pro X 10.4.0 Render Optimized Media
  • Final Cut Pro X 10.4.0 Render Proxy Media
  • Final Cut Pro X 10.4.0 Timeline Render
  • Motion 5.4.0 Emitter Export to H.264 & ProRes 4444 XQ
  • Motion 5.4.0 Graphic Heavy Commercial Export to H.264 & ProRes 4444 XQ

AppleInsider – Putting the iMac Pro thermals to the test (8-core, Vega56)

  • Cinebench R15 Multi-Core CPU
  • Wondershare Video Converter Ultimate Transcode 4K HEVC to Apple ProRes
  • Unigine Heaven

Six Colors – The iMac Pro has landed (8-core, Vega56)

  • ffmpeg WAV Conversion
  • Handbrake Transcode 1080p to lower resolution
  • iZotope RX 6 Spectral Denoise
  • sidetrack Audio Sync

AppleInsider – Review: Apple’s powerhouse iMac Pro wows with stellar performance and design (8-core, Vega56)

  • After Effects 2018 EQUILOUD Benchmark Sequence (inc. Export to ProRes 422)
  • Cinebench R15 Single-Core & Multi-Core CPU
  • DaVinci Resolve 14.2 Canon Cinema RAW Lite Playback & Export
  • DaVinci Resolve 14.2 H.264 1080p & 4K Render & Export
  • DaVinci Resolve 14.2 Motion Stabilization
  • DaVinci Resolve 14.2 Red RAW 4.5K & 8K Playback, Render, & Export
  • Final Cut Pro X 10.4 4K Motion Stabilization
  • Final Cut Pro X 10.4 BruceX ProRes 422 Export
  • Final Cut Pro X 10.4 Canon Cinema RAW Lite Playback & Export
  • Final Cut Pro X 10.4 H.264 1080p & 4K Export
  • Final Cut Pro X 10.4 Intel Quick Sync H.264 Encode
  • Final Cut Pro X 10.4 Red RAW 4.5K & 8K Playback, Render, & Export
  • Geekbench 4 Single-Core & Multi-Core
  • Geekbench 4 OpenCL GPU Compute
  • Geekbench 4 Metal GPU Compute
  • Lightroom Classic CC DNG Conversion
  • Lightroom Classic CC Generate 1:1 Previews
  • Lightroom Classic CC JPEG Export
  • Lightroom Classic CC RAW Import
  • Maya 2018 “Model Village” 640×480 Render to ProRes 422
  • Photoshop HDR
  • Photoshop Noise Reduction
  • Premier Pro 2018 4K Motion Stabilization
  • Premier Pro 2018 H.264 1080p & 4K Render & Export
  • Premier Pro 2018 Red RAW 4.5K & 8K Playback, Render, & Export
  • Wondershare Video Converter Ultimate Transcode 4K HEVC to Apple ProRes
  • Unigine Heaven Extreme

Craig A. Hunter – 2017 iMac Pro Review (10-core, Vega64)

  • NASA TetrUSS CFD (Computational Fluid Dynamics) w/ NACA 0012 airfoil CRM transport aircraft
    • VGRID Surface Mesh Generation (237,660 Triangles) Single-core
    • USM3D Parallel Performance
    • USM3D Parallel Scaling
  • Objective-C, C, & Swift Compilation w/ Xcode
  • Vectorization Speedup – Simple Add

Lomesi – With the iMac Pro, Apple promised so lightning rates: Apple T2 chip (10-core)

  • AJA System Test 64G Sequential Reads & Writes
  • Black Magic Disk Speed Test

Sander Zwartepoorte – Disappointing iMac Pro performance with Motion 5… (8-core, Vega56)

  • Final Cut Pro X Export
  • Motion Playback
  • Premiere Export