When is “Actual Size” not Actual Size?: Leopard’s Blurry Preview Pt 2 - Macenstein

When is “Actual Size” not Actual Size?: Leopard’s Blurry Preview Pt 2

My earlier post on Leopard’s seemingly soft Preview led many of our faithful readers to question my methodology, and rightly so. At Macenstein, we’ve never been the type to do “quality” experiments, and “good enough is our very best” has long been our motto. However, I decided to devote one last ounce of my precious energy to the blurry Preview issue, and the results of the test actually led to more questions than answers. (Oh, and then to some answers).

She’s actual size, but she seems much bigger to me
– They Might Be Giants

To my mind, if you open an image in Apple’s Preview, and hit the “Actual Size” button, your computer should display the image at the actual, physical size. This means, whether on a 12-inch notebook or a 30-inch cinema display, a 4 x 6 image will display as a 4 x 6 image on either screen. If you hold up a ruler, you will measure the same 4 inches by 6 inches.

And while this has traditionally been my experience with every OS X-running computer I have ever used, I noticed this was not the case on my new “Santa Rosa” MacBook.

Above: One of these things in not like the others. And it has has a big honking green arrow pointing at it. Click to embiggen.

I encourage you to “click to embiggen” the above image, not only so that you can see that I did in fact win the Great Artist Award, but also that I have placed a small yellow measuring line next to the image on each computer showing the relative 4-inch length of a section of the test photo. You can see that on all 4 of the computers (both PPC and Intel) running Tiger, the image comes up the same size. It doesn’t matter whether the image is on the 15-inch PowerBook, or the 30-inch Cinema Display. Despite running at 4 different resolutions, all 4 computers display the image correctly when you select “Actual Size”. The oddball is my new 13-inch Santa Rosa MacBook (running Leopard) which displays that same 4 inches at about 2.5 inches.

So, the question now becomes, is this because of Leopard, or is this because of the MacBook?

Well, unfortunately, no one else at the lab was in a rush to install Leopard on their machine, so I had to wait until I got home to compare my MacBook to my home computers running Leopard. Here are the results.

Above: This is a horrible photo, but you can see that the MacBook and my home MacPro, both running Leopard, display the shot at the same size, so it isn’t a MacBook thing.

So, as you can see, the sizes are identical, and Leopard is in fact the culprit, not the MacBook. In Leopard, no matter the hardware running it, hitting “Actual Size” will deliver a smaller image than doing so on Tiger.

So, why is that?

In order to achieve this universal “Actual Size” thing, what Tiger’s Preview does is actually kind of interesting (assuming you are easily interested). If you have your toolbar customized to show you the numerical scale of the zoom, you will notice that hitting “Actual Size” in Tiger will often scale an image to proportions above 100%. For instance, on the MacPro hooked to the 30-inch cinema display, hitting “Actual Size” zoomed the image to 141.11. Doing the same on the 15-inch PowerBook gives you a zoom of 136.94. What I have noticed, however, is that hitting the “Actual Size” button in Leopard’s Preview app zooms the image to… 100.

Since 100% magnification is what many people likely expect the “Actual Size” zoomer to do, it would seem at first that what’s causing this size discrepancy above is that Leopard is actually doing the correct thing, and zooming the image to 100, where in previous versions of the OS Preview did not. However, the bizarre numbers Tiger’s Preview comes up with when you hit the Actual Size button are (I think) actually doing the Actual Size zoom correctly – they are compensating for the size of the pixels on the screen in order to deliver a physical display that matches real world “hold a ruler up to the screen” dimensions. In other words, Tiger’s “Actual Size” button shows your image at the actual physical size (as the name implies), even if it needs to blow an image up to do so. Clicking Actual Size in Leopard’s Preview, however, shows you it at 100% magnification, not actual size.

I’m actually a little sad to see this feature go in Leopard, as adding an optional 100% button, or just putting the numerical scale box in the toolbar by default would have allowed confused users to see what was happening. Most users are familiar with Word or Acrobat’s size box would intuitively understand the concept. Now, we have no way to replicate the real world size trick Tiger did. Oh well, such is progress.

[UPDATE:] Faithful Macenstein reader Epyon pointed out my idiocy here in that Leopard’s Preview has an option to “Respect image and screen DPI for scale” that is unchecked by default. Checking this box makes Actual Size behave the way it did in Tiger.

But what about my claim that the new Leopard Preview is soft?

OK, well, one mystery was solved. For better or worse, Preview in Leopard handles Actual Size differently than Tiger, but what about my claim that Leopard’s Preview app displays images quite a bit blurrier than in Tiger? Faithful Macenstein reader MacDaddy had the brilliant suggestion that I install Leopard on a FireWire drive, and then boot from that on a Tiger Machine to get a truly Apples-to-Apples comparison between the two. That way, the hardware (graphics card) would be identical. So, despite that taking yet even more effort on my part, I wiped the Cheetos residue from my hands, and went ahead and did just that. See the results below.

Above: Click to embiggen. Well, what do you know? Even in a properly conducted test, my results come out the same! Leopard’s Preview (right) is definitely blurry compared to Tiger’s (left).

As you can see, I am vindicated. I set both images to a 50% magnification level (I figure 50 should be a good mathematical test bed, as Photoshop seems to display magnifications of 25%, 50%, 75% and 100% better than 33%, 66% etc.) and the Leopard image is “clearly blurry” (if there can be such a thing) compared to Tiger’s. Again, these 2 shots are from the same machine (a dual G5 PowerMac) once running Leopard, and once running Tiger.

Given that Preview in Leopard has evolved to become somewhat of an editor, one would have hoped it would be able to match its predecessors in terms of display accuracy.

So what have we learned? Well, I’d like to think that my readers have learned never to question me, but odds are that isn’t going to happen. But what we all actually did learn is Preview in Leopard is blurry, and the way Preview in Leopard handles “Actual Size” has changed as well. Is the blurriness related? I will leave that up to true geeks with their voltmeters and multi-sided die to figure out. Perhaps Core Image has changed since Tiger in a blurry way… who knows? But one thing is for certain, I won that Great Artist Award fair and square.

[UPDATE:] In the interest of shutting up faithful Macenstein reader MC, I opened the infamous fishing picture in Preview on my Leopard running MacBook, then I opened it using Preview from a networked Tiger Volume, and placed the windows side-by-side. This was by far the easiest test, and could have saved me about 4 hours of time if I had listened to MC earlier.

Both shots are set to 50%. Again, this test re-re-validates my original findings. Even on a Leopard MacBook running Leopard, if you open the Tiger version of Preview, it looks far better than the Leopard version.

Above: Click to embiggen. Should be pretty obvious by now, but Leopard’s Preview is on the left, Tiger’s is on the right.

So, is everyone Happy?

27 Responses to “When is “Actual Size” not Actual Size?: Leopard’s Blurry Preview Pt 2”
  1. Epyon says:

    For the first complaint, have you tried setting the “Respect image and screen DPI for scale” option in the Preview preferences?

  2. Epyon,


    Well, good thing I opened this long-winded masterpiece with the line “At Macenstein, we’ve never been the type to do “quality” experiments, and “good enough is our very best” has long been our motto. ”


    You’re absolutely right, I never noticed that tick box.

    Oh well, I don’t see a “Make image not blurry” check box in the prefs, so I guess the 2nd half still applies.

    -The Doc

  3. Intrepidsilence says:

    Yep, you proved it. However I would still make sure that tick (Respect image and screen DPI for scale) is set the same way on both Tiger and Leopard when performing the test because it could easily have an effect on the outcome. Our mission was not to question you but to insure that the test was sound so we can all take this to Apple and complain if in fact it is a verified problem.

  4. Anonymous says:

    I’ve also noticed the soft focus of leopards previews, but I don’t plan to ever use preview for any real image editing anyway. wouldn’t most people use iPhoto or aperture?

    why even add them?

  5. Rowlings says:

    No, most people will use Photoshop.

  6. Intrepidsilence,

    hmm, well, that s a trickier test. If you set an image to 50% magnification in Leopard’s Preview, then check the “Respect image and screen DPI for scale” box in the prefs, the image blows up to a size similar to about 75% magnification when the box is UNchecked. Therefore, a truly fair comparison is pretty difficult, as we don’t know the exact scaling formula Preview is using. I will say, however, that in an eyeball-test, the images appear to look identical, sharpness-wise (or lack there of) when you scale them to match as best you can.

    -The Doc

  7. Seth Just says:

    I have noticed in Tiger Preview that image scaling is handled without any interpolation at all when you scale: it simply makes the pixels bigger. You can see this by opening any image in Tiger and zooming way in; you’ll sell big, sharp pixels. I’m guessing that Leopard doesn’t do that, and instead interpolates a bit between pixels when an image is scaled, making it look fuzzy. However, I have no experience with Leopard, so I can’t tell you much.

  8. MC says:


    you need to grab a copy of Tigers preview and run it under Leopard. That way you can see if it’s Apples core graphics making the blur or the new preview app itself. Like I said in your first article.

  9. doug says:

    That’s a pretty sweet setup you got their at the lab. Do you have a wider shot? I love seeing where people work.

  10. Kev says:

    I just tried this out myself and it even seems to happen when images are at 100%. I’m running on Leopard and just using my old Preview from my Tiger install.

  11. Luis says:

    Hi guys, I just installed Leopard and found that one of my favourite apps is not doing its job properly. As I still have Tiger on another disk (I’m just evaluating Leopard to see how it goes) I opened the same image with Preview 4.0 (Leopard) and Preview 3.0.9 (Tiger) side by side, both images set to fit in the window and clearly Preview 4 is blurrying images, while 3.0.9 remains crisp and detailed.

    I also opened the image using Quick View and it shows the image OK, the same as Preview 3.0.9, so I think we really have a problem here with Preview 4.0 not handling “fit to window” the way it should. I don’t use Preview for editing but I find it most useful when I design say different versions of a poster and I want to look at all of them at the same time with exposé. Cheers!

  12. Alex says:

    I’m nowhere near my mac at the moment, but is it possible you’re running different anti-aliasing prefferences on the two machines?

    It’s possible that in the course of using Tiger you modified an anit-aliasing setting that you ave not yet changed to your liking in Leopard.

    I’m not sure if that would matter if you open an image using preview from a mounted tiger volume, but it’s worth exploring.

  13. f1sh3r says:

    The same check box exists in Tiger, “Respect image DPI for “Actual Size”.”

  14. Steve Haskayne says:

    Click to embiggen dont you mean enlarge?

    also has this guy checked what resolution the screens are running as that might have something to do with it?

  15. Wes says:

    @Steve Haskayne
    “embiggen, coined by Dan Greaney, means “to make bigger,” or, used symbolically, means “to empower”.”

  16. Jason says:

    Have you looked at the image in Photoshop and compared to Preview in Leopard and Tiger? Sharper in not necessarily more accurate, and it could be that Preview in Tiger was performing some sharpening on the image.

  17. Jason,

    Yes, Photoshop renders the images identical to Tiger’s Preview.

    The good news is, Leopard’s blurriness seems to be a display issue only, as when performing a resize or something in Preview 4, the resulting image will display sharp in Photoshop (but not in Preview, of course).

    -The Doc

  18. Jason says:

    Cool. Just thought I’d see if you’d checked that before I spent the time testing it 🙂

    Here’s looking forward to 10.5.1!

  19. Bruce says:

    re. the sub-thread ‘what will most people use’ for their actual graphics manipulation, rather than the Preview app:

    I’d add GraphicConverter ($35) to the short list of iPhoto, Photoshop ($600), or Aperture ($300). Reason being that GraphicConverter is a popular low-priced alternative graphic app. (esp. compared to the high prices of Photoshop and Aperture).

  20. Bruce says:

    re looking forward to 10.5.1 (with the historical OS X first .1 release coming 3 to 5 weeks after the .0 intro).

    The article from AppleInsider lists what they know about the fixes in 10.5.1, and Preview is NOT listed as an issue. 8-(


  21. imajoebob says:

    Can you run a test where alter the image in Leopard Preview, then compare the new file in both? That might expose if it’s some kind of display/rendering issue versus a program defect.

  22. imajoebob ,

    I did already, see comment #17.
    It seems to eb a display only issue.
    -The Doc

  23. Anthony says:

    Interesting find. A couple weeks back, I noticed that Aperture’s exports under Leopard were much softer than the same exports done previously in Tiger.


    I wonder if the problems are somehow related?

  24. late says:

    Not only the preview is soft, but if you export version to t.ex. desktop and then send it to your homepage the photo is soft. Aperture under leopard seems to be useless if you use it for editing your photos for forthcoming use. THEY ARE ALL SOFT DAM. I just downloaded my computer back to Tiger and now it is ok. NOT OK, I HAVE PAID FOR LEOPARD AND APERTURE.

  25. Don KIng says:

    Nice to see you mentioning this size problem in Preview. It’€™s been driving me crazy from day one of Leopard. And it is a problem. The bottom line is: actual size should be actual size. And it isn’t in Preview anymore. Anyway, after reading the suggestion of checking the box ‘Respect image and screen DPI for scale,’ I open the Preview Preferences to see what I had checked. And I did in fact have the box checked (I guess I changed it from the default a while ago). But I still wasn’t getting actual size previews. And it doesn’t matter if I have ‘€˜Actual size’€™ or the ‘€™Scale large images to fit window’€™ checked. Either way, with the ‘€˜Respect etc.’€™ box checked, the preview just wasn’t actual size. NOW HERE’€™S THE STRANGE THING: if I uncheck the ‘€˜Respect etc.’€™ box, actual size finally comes in!!! Yes, uncheck the box. Just the reverse of Epyon’s suggestion. Maybe I’€™m living in a parallel world here in New York City (some would say I am). And here’s a neat trick: you can see this whole thing happening by keeping your image open (in my case a .jpg) and check and uncheck the ‘€˜Respect etc.’€™ box. The image ZOOMS up to ‘€˜larger than actual size’€™ and then back down to ‘€˜actual size.’€™ I stopped trying to figure it out. All I know is I finally get actual size images in Preview. At least until I get back to the real world (hopefully not too soon).
    Signed by a confused but happy,
    Don King
    Graphic Designer/Art Director

  26. johnny says:

    Don King:

    Actual Size refers to the size of the image as printed in the real world, YOU RETARDED IDIOT. This means that it has to take into account things such as
    DPI in order to achieve resolution independence.

    Get a fucking clue.

  27. Æ says:

    Well, I just blowed in off Google and can’t claim to have a clue, but there IS something about Preview that just drives me crazy. (Running 10.4.11 by the way.) Everything looks normal, I hit print, and Preview has perversely decided to resize the scale to 53 percent. WHY???

    I use Preview only to open and print pdfs. It’s like nagging a kid to do its chores. If I don’t click “preview” in the print dialog, it’s likely to spew out pages of tiny print. If it’s gone into its 53 percent fetish again, I can reset for 100 percent in Page Setup, but for that document only. The next time I open a document, here we go again.

    At the moment, I don’t have “Respect Image DPI for ‘Actual Size'” checked in the Images preferences. In the PDF preferences, I do have “Use Scale” checked and set to 100 percent. Neither seems to make much difference.

    Has anyone found a way to deal with Preview’s size fetish, so that it stays fixed?

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