Web images are 70ppi, rMBP is 220ppi. What does this mean for Web Images?

Discussion in 'MacBook Pro' started by GCWB, Jul 8, 2012.

  1. GCWB, Jul 8, 2012
    Last edited: Jul 8, 2012

    GCWB macrumors member

    Sep 1, 2010
    Thread Closed. Please do not reply. I made a newbie mistake.
  2. Aodhan macrumors regular

    Jun 16, 2012
    It means they're not going to look too good. See here please.
  3. GCWB thread starter macrumors member

    Sep 1, 2010
    I apologise... I did a search, and I actually did see this thread. Just didn't think it answered the question as directly as I had wanted. My bad.

    In fact... I'd like to keep this thread active. As I think whilst it's very similar to the article you mentioned... I wanted to directly ask this ppi question. I agree though, it probably would be more appropriate to be in that thread. Seeing as that I've already made it... why not get the direct suggestions I was looking for.
  4. leman macrumors G3

    Oct 14, 2008
  5. cathyy macrumors 6502a

    Apr 12, 2008
    It means absolutely nothing.

    Web images are calculated in pixels, not pixels per inch. The 72 DPI standard for web is a myth and does not affect a thing. Read here: http://www.webdesignerdepot.com/2010/02/the-myth-of-dpi/

    If you compare the same image on 220 PPI monitor and a 110 PPI monitor at native resolution, it simply means that the picture would be twice as big on the 110 PPI monitor. Or if you're confused by this, then just imagine watching a Full-HD movie on a 7" iPad 3, or a 42" Full HD TV. The picture quality remains the same on both screens, but it's a lot smaller and more crisp on the iPad 3 due to it having smaller pixels.

    The problem of pixelated images on the Retina MBP comes due to Apple's weird resolution scaling. If you could run the desktop at true 2880x1800 resolution, there would not be any pixelation or blur-ness of images.
  6. GCWB thread starter macrumors member

    Sep 1, 2010
    My bad. I think I was referring to DPI as opposed to PPI. I'll read that link though, wasn't aware it was a myth. Thanks.


    Sorry, Google is usually my initial line of inquiry, yet after an initial search on Macrumors and resulting with no results... I felt like it would be an interesting discussion.

    Seems I made a few mistakes with my initial question.
  7. leman macrumors G3

    Oct 14, 2008
    Well, it works a bit differently when resolution independence comes into play (like OS X HiDPI modes). Here, a logical pixel (point) equals two real pixels. For example, the 'best for retina' mode is logical 1440x900 and is seen by applications as such, its just that real resolution is 2880x1800. Basically, for the HiDPI mode the physical size of a 'normal' 100x100 image and a HiDPI 200x200 image will be the same: 200x200 (the normal one will be upscaled using bilinear filtering). I agree that its a bit confusing, but its the way it works. We are used to the fact that pixels represent the image size. With resolution independence, pixels represent image data, and not longer the image size, which becomes a separate parameter. So a 1x1 cm image could be 50x50 pixels, 100x100 pixels, or 1000x1000 pixels, hence HiDPI. Of course, OS X uses a bit simplified notion by distinguishing only between HiDPI (1 pixel of image = 1 native pixel) and non-HiDPI (1 pixel of image = 2 native pixels). It would be probably less confusing to work with real units, like mm, and design the UI in true resolution-independent way. But its something for next-gen OS.

    Apple developer documents provide a nice overview: http://tinyurl.com/d7kr95d
  8. gentlefury macrumors 68030

    Jul 21, 2011
    Los Angeles, CA
    Actually the UI elements in OSX are 4x larger than they traditionally would be to display properly on Retina. A typical icon is 256x256...the retina aware icons are 1024x1024. This is because the "best for retina" setting is a 2x scale. But remember you are scaling 2x on a screen that is 2x higher res than it is scaling to...so the UI elements have to actually be 4x in order to render at the correct size in full res.
  9. cathyy macrumors 6502a

    Apr 12, 2008
    Understood, but the TS's query was regards to the rMBP's 220 PPI, rather than Mountain Lion's queer resolution scaling.

    Should be 512x512 = 262144 pixels, which is 4x more pixels than 256x256 = 65536 pixels.
  10. leman macrumors G3

    Oct 14, 2008
    This is what I wrote, yes.


    A quick note: its not Mountain Lion, its been in there since Tiger I think, but only Lion has a more or less feature complete implementation.

    And I think I know what you mean. Its just thats its very confusing just trying to recognize what the question was and which question does an answer actually answer :) I just thought that it could be helpful to explain the resolution independence just in case some people who read this are interested in this part of the question.

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