Confused about scaling on 5k iMac

I too just bought a 5K iMac 27" (with a Radeon Pro 580 graphics card) and am also puzzled by the resolution schemes. When you go to system preferences>display you can choose "scaled" but the highest resolution you are "offered" is 3200 x 1800 (more space as it is called). Why can't I choose for the native resolution 5120 x 2880?

Don't know if this helps.

2560 x 1440 is the default resolution.

For other resolutions goto System Preferences > Displays > Hold down Option Key and you should see a Detect Displays marker in the lower right hand corner.

Now change the Resolution from Best for Display to the Scaled option and you should be presented with a drop down list of available resolutions including 5120 x 2880.

Concerning the OP's question re Preview, I've found that Preview will not accommodate different resolutions. It's a one size fits all. Cn't answer re iPhoto as I don't use it but someone in that section may well have the answer or explanation.

I just got the new iMac 5K and was also having issues with Preview at 100%, but found a solution:

Go to Preview>Preferences>Images and change to this:

The text doesn't seem to make sense (the "1 image pixel equals 1 screen pixel" should be the correct option, right?) but it seems to work.

It's a new machine, so you have at least 90-days of free phone support. Contact Apple's Support and they'll handle all of you questions. BTW, I strongly recommend getting AppleCare Protection Plan. It's the best warranty policy available for desktop machines and gives you three years of free phone and repair support.

27" i7 iMac (Mid 2011) refurb, OS X Yo (10.10.1), Mavs, ML & SL, G4 450 MP w/10.5 & 9.2.2

I also got a new iMac 5k yesterday and noticed exactly the same thing. Quite disappointing! Selecting 'Actual Size' in Preview is pixel doubling the image and making it look awful. And iPhoto doesn't give any info about when you're at a 1:1 zoom.

However, Adobe Lightroom works beautifully and correctly displays images at 1:1. The detail is breathtaking! I highly recommend you try downloading the free trial just to see it.

What's kind of staggering is the my display now has more pixels than many of my cameras' sensors (all but my high-end Canon DSLR)! An 8 megapixel image from an iPhone 6 only fills 75% of the screen vertically, so you can see every pixel and room to spare for editing tools.

Let's hope Apple gets their act together soon on iPhoto and Preview for Retina displays -- it's kind of pathetic.

Hello Chris,

I am experiencing the same problem. I am wondering if you did get an answer to this or maybe someone else. Please help because it is very confusing. In QuickTime for example I am playing a 4k video, but it says it is playing at 2560x1440. However I'm not sure if this is true, cause changing the settings from the lowest to the highest resolution (scaling options) does not really seem to affect the sharpness and quality of my full screen video.

However I am lost on this topic.

The first section in the following link may help to better explain it's resolution:

http://www.everymac.com/systems/apple/imac/imac-aluminum-tapered-edge-faq/how-to -run-imac-retina-5k-at-full-resolution.html

I had already discovered the excellent tip seroposi suggested (saw it on an iMac 5K at an Apple Store). What's interesting is then to compare images and movies using the max (5120 x 2880) resolution, versus the 'best' scaled resolution (pixel doubled). I played a 4K movie in Quicktime at both resolutions. When I used max resolution, I could use 'actual size' and get 1:1 pixel mapping. Using 'best' scaled, I had to guess where "50%" was, since neither Preview nor Quicktime seem to give you this information. Anyway, when I took screenshots of both, I got identical pixel to pixel results...

So, this means that while most of the native Apple apps (QT, Preview,iPhoto) are displaying content correctly (i.e. not pixel doubling images & videos), the 'Actual Size' calculation is wrong and doesn't give you any easy way to get a 1:1 mapping. It's interesting that Final Cut Pro does actually know what a 100% playback looks like, even when on 'best' scaling. So clearly Apple knows how to do this. Let's just hope they fix them in future versions of these apps.

Thanks seroposi and bryston! I find this option to use the max resolution helpful. However everything is indeed crazy small. Now I compared for example a 4k video on Youtube (just for testing) and it does not matter for the quality of the video itself if you set the resolution to max (5k) or for example 1280x720 when you enter full screen. It seems like the iMac forces it to play 4k anyway. Probably the same for VLC and other programs. Can you agree to this?

However I also keep reading that QuickTime does not support playing 4k videos. An employee of Apple (support employee) told me this. And I read VLC does. What are your thoughts on that?

FWIW, the setting you chose will show how large the print out will be based on the resolution the printer is set to if you choose Actual Size.

The first setting will display a 1 to 1 correspondence on the screen based on the resolution of the image when viewed at Actual Size. So if you had a one inch image that is 300 dpi, it will display using 300x300 screen pixels. a one inch 72 dpi image would use 72x72 pixels on the screen and so on.

You are right, I think I was testing the wrong image, one that I had exported at double the dpi as a test (and then, having the exact same pixels but double the dpi, showed it as 50% the size and not pixelated)

So it seems like there is no way of resolving this until Apple decides to do so, correct?

Sorry, I suppose the issue then is that it is a retina display.

I suppose there are two issues here that Chris (first post) has mentioned.

One is that pictures in preview seem pixelated when displayed at "Actual Size", and the other is about watching a 5K video with quicktime.

The first one seems to be related to the fact that it is a retina display, and the other is that this retina display (the newest iMac) is also 5K.

I was trying to understand if there is some setting I have to change in preview to see the picture at the actual size with my retina display, where one image pixel is actually one screen pixel.

Okay. First, are you using "Default for the display" in the Display settings or Scaled"?

I didn't see where Chris mentioned pixelation but if I view a 5120x2880 image in Preview at actual size it is not pixelated.

I can't speak about 5k videos because I wasn't aware there are any. I do watch NetFlix 4k Ultra HD videos in full screen and they look great.

I'm probably just missing the point somewhere.

I'm using "Default for display"

The picture I am using has 700px per 394px. I see it at the correct size in Photoshop but preview shows it bigger and pixelated when the "Actual Size" is selected. So technically it doesn't seem to interpret one image pixel as 1 screen pixel... more like 1 image pixel is 4 screen pixels.

I'm now thinking this might be a different issue, do you think I should open a new thread for this issue in particular?

(on a side note, I haven't found any 5K footage either, I don't think it exists, 4K from a video on youtube looked amazing)

I see, (I Think) 😁

The 5k Macs are 218 p.p.i. That can't change no matter what. I don't use Photoshop anymore but it just sounds like it's using a better or different method of scaling. Neither is correct however. Only if you had some 218px images to look at would it be a true 1to1 correspondence.