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Judging by the comments to my question, I should maybe paraphrase my question. Original post below.

The problem:

If I take a screen shot on my Retina Macbook, with a display resolution of 2560x1600, the saved file cannot be opened on the same machine at resolution 2560x1600, but needs to be rescaled to 50% (at least in Preview and XnViewMP).

My questions:

  • Why is this the case? Why can't I open a screen shot at 100% on the display the screen shot was taken of?

  • Is there a real solution for this? By "real solution" I mean, not a workaround that simply rescales the image to 50%, and as a result, will make it look somewhat blurry?



(Old version)

I'm aware that this problem -- of screen shots taken on a Retina Macbook looking bad due to some "resolution mismatch" -- is a known problem. It's been covered for example here.

However, I'm trying to figure out what exactly is going on, because right now I don't even understand what causes this problem:

If I take a screen shot on my rMBP 13' at a screen resolution of 2560x1600, the file that is saved has the same resolution, but opening it on the same machine, it looks a lot worse.

It seems that opening the 2560x1600 file on the same machine/display can only be done by scaling the image down 50%, to 1280x800.

Now, I understand that the blurriness I see is due to the rescaling of the image (to 50% of the file resolution), since rescaling (never?) works absolutely perfect.

Here's what I don't get: I can see how opening a Retina display screen shot on another (non-Retina) display would lead to this problem. But I don't see why, on the same machine and display, the screen shot I just took needs to be scaled to 50%.

Could anyone take a moment and explain why that's the case?

P.S. I realize that there are some workarounds which all seem to involve rescaling the image "on the go", as described for example here, or by using apps that do it for you (e.g. RetinaCapture).

However, none of these solutions solve the problem described above: that the rescaled image will look (slightly) worse than what I see on the screen, and of which I want a 1:1 screen shot.

(EDIT) Okay, just figured something out: When opening the 2560x1600 screen shot with an app called 'Acorn' (which I just downloaded, only trial mode), it looks perfect. So it seems to be somehow related to the image viewer. I tried before Preview, XnViewMP and Gimp -- on all of these the, the image is scaled down to 50% to display it entirely. Anyone knows what the difference is, and if I can set any of the above programs to perform like Acorn?

(EDIT 2) A comment by user duozomo in this A.SE question suggests that the problem is due to different image viewers using different parameters for "screen pixel per image pixel". Can anyone confirm this? And if so, is there a known list of which programs use which parameter for this?

  • I'm not really sure what you're asking here. – At0mic May 8 '16 at 20:52
  • I take a screen shot (with my display set to default 2560x1600). I open the screen shot on the same machine (with Preview, for example), and it needs to be scaled down to 50% to be visible entirely. Why? – Bert Zangle May 8 '16 at 21:07
  • Do you want an explanation as to why this is the way it is or are you looking for a workaround/solution? I am not clear on what you are asking here. – Allan May 8 '16 at 22:03
  • @Allan Both, ideally. Right now, I don't see why this the case, so I don't know if a "principled" solution is possible in the first place. And, like I wrote in my question, the only workarounds I've seen so far seem to amount to "on the fly rescaling", which doesn't lead to a high quality screen shot. – Bert Zangle May 8 '16 at 23:14
  • Rewrote the question completely. Better now? – Bert Zangle May 9 '16 at 8:11
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A Retina display's default resolution is 1440x900. I believe the screenshot feature takes a screenshot of what the monitor "seeds", so a 2560x1600 resolution of a 1440x900 screen.

I'd have a look at RetinaCapture, an app designed to take screenshots on a Retina Mac.

  • Hey. Thanks for your help! I already looked at RetinaCapture, but it seems that all it does is take a 50% resolution screen shot in addition to the regular one, so the "blurry because rescale" problem persists. – Bert Zangle May 9 '16 at 8:12
  • I beg to differ, my retina mid-2014 13" MacBook has a screen resolution of 2560x1440 and has no problem taking (with ⌘⇧3 or ⌘⇧4) and opening screenshots at full resolution. – perhapsmaybeharry May 9 '16 at 8:19
  • @perhapsmaybeharry That's odd. What are you using for viewing the image, if I may ask? Finder, or some other program? – Bert Zangle May 9 '16 at 18:49
  • Preview seems to work nicely. Are you not using Preview? – perhapsmaybeharry May 10 '16 at 1:48

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