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5K iMac 27-inch 2015 review

evan kypreos




  • Editors choice

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  • iMac 5K screen
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  • iMac 5K screen
  • iMac 5K performance
  • iMac 5K performance


Our Score:



  • Still a great design
  • Incredible 5K Retina screen
  • Solid performance with Skylake chipset and discrete GPU
  • Rechargable keyboard an improvement


  • Not ideal for gaming

It might not have gained as many plaudits as the iPhone 6S, but last year's 5K 27-inch iMac was a revelation. While it looked identical to its predecessor, the pin-sharp screen was an enormous improvement.

In 2015, Apple brought the Retina-quality display to the 21.5-inch iMacs too – this time 4K – but it’s the big, 27-inch model I'm reviewing here.

Of course, the headline feature of the 2015 iMac is that 5K 27-inch display, to which Apple has made further improvements. It now comes with an even greater range of colours, thanks to the use of a new colour space more commonly used by film types in Hollywood.

Running the latest version of OS X, El Capitan, the new iMac also incorporates Intel’s newest Skylake chipset to boost both performance and efficiency.

All these components combine to make the best all-in-one personal computer you can get right now.

iMac 2015 – Design and Connectivity

It’s easy to be blasé about the iMac’s all-metal-and-glass style. After all, it’s been around in this form since 2013.

That would be doing it a disservice, though. The iMac remains one of the best-looking computers you can have on your desk.

A metal stand holds up the screen and slim body, which manages to fit in a plethora of high-end components – including a discrete graphics card. The iMac isn’t a table ornament; it’s a workhorse, albeit a very pretty one.

5K iMac 19

While the tapering rear is sleek, the screen bezels are chunky, especially when compared to more recent TVs and their impossibly thin bezels. This means it’s even bigger than it needs to be. And it is big, thanks to that 27-inch screen.

The stand enables you to tilt the screen up and down, but there’s no way to raise it unless you use a pedestal, which is a shame.

In order to keep the sides as thin as possible, Apple hasn’t included an optical drive. Those who desperately need one can buy an external USB SuperDrive. This isn’t quite as heroic as it sounds, however – it’s only compatible with DVDs and CDs, not Blu-rays.

There is a decent amount of connectivity, with all of it located on the rear of the iMac. There you'll find an Ethernet, four USB 3 and two Thunderbolt 2 ports. The latter offers support for up to two 4,096 x 2,160 external displays, or a single 5,120 x 2,880 dual-cable external display in addition to the iMac's built-in screen.

5K iMac 25

There's also a SDXC card slot, for getting photos off your camera, and a headphone jack. Having to reach around the giant iMac to get to these isn’t easy, though, especially if you've chosen to position the computer against a wall or window. Bluetooth 4.0 and dual-band 802.11ac Wi-Fi complete the connectivity array.

The iMac comes with a pair of built-in speakers that offer enough volume to watch videos and listen to music comfortably. Hidden away in the back, they're down-firing units that are actually pretty decent, especially considering how unobtrusive they are.

Finally, a HD FaceTime 1.2-megapixel camera can be found at the top for video calling. It's a little underwhelming but still adequate for Skype calls.

5K iMac 2015 – Screen

27-inch Retina 5K IPS TFT display; 5,120 x 2,880 resolution; DCI-P3 colour space

iMac 5K screenThe 5K iMac is all about the screen. Apple has worked hard to make this display very special indeed.

Let’s start with some of the tech behind it. Apple has included an “organic passivation” layer that sits directly behind the pixels. Combined with the oxide TFT layer, this reduces the amount of crosstalk between pixels, ensuring there’s no pixel bleed and that the display is crystal clear.

But the main upgrade to the iMac 2015 is that it now supports a much larger colour gamut.

Last year’s 5K iMac, while incredibly sharp, didn't quite hit the mark when it came to Adobe RGB colour coverage. This year's iMac uses the DCI-P3 colour space.

This has been used by cinemas since 2013, because it provides a larger range of colours – particularly reds and greens. In fact, it covers 100% of the colours you can see in sRGB, the most common standard for monitors, plus 20% more.

It also compares favourably with the wider Adobe RGB. DCI-P3 covers 93% of Adobe RGB, whereas Adobe RGB covers 87% of DCI-P3. DCI-P3 offers more of the red and green, where Adobe RGB does more with blues.

Both offer more colour choice over sRGB – the standard for almost everything on the web. Photographers, graphic artists and, in particular, videographers will appreciate the extra range the iMac offers.

All this results in the iMac 2015 having an incredibly natural-looking display, closer to reality when compared to any, hugely expensive, non-professional monitor I’ve seen before. In particular, switching between sRGB and DCI-P3 when looking at RAW camera photos is a real eye-opener.

I examined dozens of photos, playing spot the difference. Initially it was tricky to determine where the changes were – slightly better colour accuracy here, a little more detail there. The effects were far more pronounced with pictures dominated by reds and greens.

An image of some raw red meat barbecuing (apologies to vegetarians) showed far greater detail and texture in DCI-P3 that was blown out in sRGB. It was the same story in an image of a bright red parrot, where individual strands of plumage became visible. Similarly, green forest scenes were packed full of nuance and shades that just wouldn't be visible on most other monitors.

This is a bright screen, too. At maximum brightness it delivers an enormous 480 nits, but most will want to tone that down to something more manageable. Far more comfortable for the eyes is a setting of 50% brightness, which offers 180 nits.

5K iMac 1

At this level colour temperature sits at 6,474K, which is only a smidge away from the 6,500K ideal – and it means the natural look of the screen and accurate whites are born out in testing. Contrast ratio, too, was impressive at 1,176:1, with the screen delivering plenty of detail in low-light images and video.

The impressive numbers don’t end there. A Delta E level of just 0.22 means that the iMac offers professional quality colour accuracy too. All this means that not only is the iMac's screen the best you can get in an all-in-one, it is one of the best monitors you can get full stop.

If you’re into video editing then the high pixel resolution will be a real boon. It means you can edit 4K video in full resolution in a window, with all controls also on-screen.

iMac 5K

Note that the screen isn't a matte panel, so there will be some reflections. However, it’s manageable and will be less of an issue for a desktop that won’t be moved around much.


November 19, 2015, 10:09 pm

there is simply no reason to get the iMac without an ssd drive even if you can afford the smallest one. Spinning drives are pretty much the biggest bottlenecks in modern machines. Besides, the more than capable thunderbolt expansion port is far more versatile when it comes to storage expansion.

Mark Southee

November 20, 2015, 11:04 am

You can get a Samsung USB BluRay burner for very little money. That's what I got.


November 20, 2015, 12:37 pm

It's still a lot of money though, isn't it?
For the price you could get a good similar spec Windows PC, screen and decent laptop/tablet as well.
And you wouldn't have to run Mac OS ;)


November 20, 2015, 3:40 pm

But is it really a lot of money though? lets break it down,

If we take the mid range 27" model which is £1599

The 5k monitor has no current rival, the closest being the Dell 5k monitor which is around the £1000 mark and updated iMac panel still has a higher colour accuracy.

that leaves us with £600 which is what a comparable PC tower will cost anyway. I'm not even including the 'apple tax' or taking the build quality into account.

Personally I think this is the first time iMacs trade blows with PCs on a level field


November 20, 2015, 4:53 pm

oh the haters are out.


November 20, 2015, 4:57 pm

Not really a hater, just can't agree to a 10/10 score for these devices any more. There are, unarguably, better alternatives for most of the market to spend that much cash on.

Don't have enough energy in me to be hating on a tech company. Buy what you like, it's your money.

The Mac Os comment was intended tongue-in-cheek, hence the little winky face thing.


November 20, 2015, 4:59 pm

that money will hold its value very well compared to what you mentioned as an alternative


November 20, 2015, 5:20 pm

If resale value is a key aspect to your purchasing decision, then yes, an Apple device may be a good choice.

Premium Windows PCs hold their value well too, but unless you've looked you might not guess it.


November 20, 2015, 5:31 pm

if value wasnt why bring it up in the actual purchasing, it would simply be about user experience of the said device.

price would not be an issue, and they don't hold it as well or are as easy to move as a mac.

Tule Trooper

November 20, 2015, 5:40 pm

Only the 1 TB fusion drive has the 24 GB SSD. The 2 TB and 3TB have a 128 GB SSD


November 20, 2015, 6:19 pm

Wow - MattMe, in that one exchange you have expanded Paul's normal contribution to anything Apple a thousand percent! There's no doubting that this iMac is a very decent machine and although expensive, I somehow expected it to cost more. That said, I like building my own PC's and, for that money you can build a stonker of a PC with more power than the Mac. Horses for courses. Take your pick.


November 20, 2015, 6:29 pm

Well, personally when purchasing a device like this (£1.5k desktop) I'd plan on keeping it a while and getting my money's worth out of it. That's why I wouldn't usually take resale value into account.
Particularly because that's in the future and you've no idea what will happen.

I'm not sure what you're comparing exactly, as I didn't mention any devices, but I promise you that particular brands of windows computers are just as easy to sell and hold their value as well as Macs.
It's supply & demand.
Alienware and Razor are two such manufacturers that come to mind.

Prem Desai

November 20, 2015, 7:17 pm

Decent enough kit. Not awesome any more as it was 2 years ago.

If any other manufacturer had made a device that didn't have a height adjustable screen, they would have been slated - especially at this price.

And the ports at the back!!! What's with that??? You can't see what port you're plugging into and you're guaranteed to scratch the metal finish. What idiot designed this?

For me, the screen is the star - in my opinion, 7/10 at best.


February 4, 2016, 8:20 pm

Hi can your machine edit High definition (not 4k) without any Judder. I have a fairly powerful Chillblast Machine from 2012 but because my editing software uses the processing chip for editing It's almost impossible to edit in HD because it judders all the time. The software package is Serif move plus 6. Chillblast recommend I switch to Sony. Thanks

Raymond Psaila

February 4, 2016, 8:46 pm

I have no judder at all In HD Or in 4 k Editing On my iMac or iPad Pro both with Final Cut Pro Donald


February 4, 2016, 8:56 pm

Thanks very much I think I'm going to change my equipment and give my PC to my Nephew to help his study for his maths degree. I'm very interested in the relationship of music to moving image and I need pinpoint accuracy when I'm editing. Just finishing off my original Star Wars film battle against the Death Star with new music,

Raymond Psaila

February 4, 2016, 8:57 pm

I gave 10/10 But I bought It and that Is An Honest Score From A Owner (sorry MattMe) I happen to love and Enjoy my late 2015 iMac, iPad Pro with it apple pencil , Apple TV 4 with games controllers And the Apple watch. Not everyone can afford the kit I have and I wish everyone well with what they Have ......... I absolutely love My Apple set up.

Raymond Psaila

February 4, 2016, 9:02 pm

Your welcome Donald I have No Regrets at all........ not one Sir


February 4, 2016, 10:26 pm

Clearly you're an Apple fan, and quite a wealthy one at that.
I wouldn't expect someone who had invested so very heavily in the Apple range to have anything else to say.

I hope you enjoy every single one of the precisely mentioned products you own.
I am also very happy for you that you can afford it all. It is shame not everybody in the world has the comfort to choose to do the same if they do wished.
Don't forget that some people do prefer (and will consider) other products, and that does not necessarily mean that they cannot afford Apple devices.

Raymond Psaila

February 5, 2016, 12:06 am

Ok MattMe before i get to bed I thought i would put you strait on a Couple of items in your above reply FirstlyI am not wealthy I am disabled and mostly house bound man, I used my life saving to buy my Apple set up and like every person who might take the time to read my review it to was a very very considered purchase, I like value for money like every other person of my age (61) . Secondly I have sat in front of a HP iQ830 23" touch screen all in one desktop Pc running Widows Vista home premium for the last 10 years 4GB and 3TB of Hard Drive Space, I used it to edit Visa Paralympic games Photography that i use to Shot from 2002 Until 2008 I used to Be an official photographer for the International Paralympic Games In Manchester over that time even though I disabled myself since 1987. On the HP it used to take me hour to edit Images and on the Apple It Would have and now takes me seconds to do the Same Work, I did not get paid for any work I did. I love getting out of my home to work shooting of disabled people striving to concurring there own goals in life. I know not every one has the own limits and budgets that allow them to buy what is in there Budget Every one has the right to save for what they feel is better for them Or blow what ever life saving they have on what them dream of changing there world Apple has Change my World on more way than you can understand and that only that you do not know anything about people like myself who strive to have a system made by one the most advanced companies in world that links its technologies as I enter my info into one for it to be updated on every bit of my setup and the click of an enter key or to chat live with my friends who also Live by Apple Products world wide on Face Time for Free as i can on my phone iPad apple watch or even my apple tv ..... Name me one other Company up know Of that can do that at no extra Cost ........ Thats My Last Words MattMe Your reply Will not be needed Thanks I'm done reply to you Sir oh I am not what you would Can And Apple Fan " I a very happy Apple Owner and happy to disappoint you. I own my Dream System and truth be told you pay for what you get in anything in life .


February 5, 2016, 12:32 am

Really so much of this is not relevant to the conversation I'm not sure where to start.
Your performance issues were not because you weren't using an Apple product, they're because you weren't using modern hardware. And you were using Vista, which really does say a lot about the type of computer user you are ;)
Apple products are really no faster than anything else using the same hardware. It's all Intel stuff at the end of the day.

I don't care if you use Apple products, Samsung products or Asda own brand products. So long as we're talking in truths and not personal opinion dressed up as truths.

You cannot use Facetime on your Apple watch. I think you must be confused about that. I believe you can initiate a call from your Apple watch if you wanted to for some reason.

You can use Skype to talk to your mates for free, or Google Hangouts and they both have the excellent advantage of not relying on all the people you want to communicate with also owning hardware made by one particular brand. You can use them on all platforms including your home PC or macbook. They're far more convenient.
How is that getting what you pay for?

I know a lot of disabled people, they all get on fine without Apple products. I'm not really sure what point you're trying to make.

Sorry, I don't mean to be argumentative, but I don't appreciate folk pushing their opinion as facts.
And also telling me my reply won't be needed? Guaranteed way to get me to reply :)

Best of luck to you, my man.


March 5, 2016, 2:43 am

Evan, is there any way to know whether this imac is approved by FDA. I've been searching high and low regarding its possible use for radiographic imaging. I have grey-scale 5MP eizo monitors, but the possibility of combined usage with osirix in this is intriguing

Nathanael Davenport

April 9, 2016, 6:54 pm

Yeah, the ports in the back are a minor annoyance, but for me, at least, that's all it is. Minor. Reaching around the back isn't the biggest deal, especially since I use a USB hub and end up putting flash drives in there anyway. Your tone is a little harsh for a trivial issue.

Nathanael Davenport

April 9, 2016, 6:55 pm

Also, see this is you have to have something near your screen:



May 12, 2016, 9:40 pm

MattMe: If it makes you feel any better, I have a 3yo HP PC that's really quite OK, running Win7 (but keep getting badgered to upgrade to Win10), and I'm looking to replace this with a 27" iMac. I'm fed up to the back teeth with Windows. I also use OS X, and my wife has a 27" 4k iMac, it's very nice. Since I don't game, i think the 5k iMac will be a good option. You can be as dismissive as you like.

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