Does anyone know the resolution the iPad uses for photo displays?

Discussion in 'iPad' started by Piggie, Jul 11, 2010.

  1. Piggie macrumors G3

    Piggie

    Joined:
    Feb 23, 2010
    #1
    As I understand things.

    If you resize an image on your computer using photoshop to 1024x768 then it will look fine on the iPads screen, but if you try and zoom in (multi touch) then you won't see any more quality in the image (as you would of course expect)

    If you try and sync a MASSIVE file to the iPad then there will be more quality to zoom in and see on the iPads screen.

    But I don't expect the iPad (when you sync with iTunes) does keep a MASSIVE image at it's same size. I guess some resizing is done to avoid storage memory being wasted.

    I wondered if anyone knew the real X/Y image size that iTunes/iPad will resize images to when you sync some very large pictures onto the device.
     
  2. darngooddesign macrumors G3

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    Jul 4, 2007
    Location:
    Atlanta, GA
    #2
    I would imagine it resizes to the screen's resolution. 1024 x 768.
     
  3. BrennerM macrumors regular

    Joined:
    Jun 17, 2010
    Location:
    Kitchener, Ontario, Canada
    #3
    It is definitely more than 1024x768 because there is more detail if you zoom. I estimate it is around 2500 pixels wide, but I have never seen anything from Apple that confirms an exact resolution.
     
  4. Battlestar macrumors 6502

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    May 9, 2010
    Location:
    Boston
    #4
    There are other ways to get the images on your iPad besides syncing them with iTunes.
     
  5. b.c. macrumors 6502

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    Nov 5, 2008
    #5
    based on my testing, iTunes resizes photos to 2304x1536 if originals are larger than that, before syncing to the iPad

    http://forums.macrumors.com/showthread.php?t=963853
     
  6. Piggie thread starter macrumors G3

    Piggie

    Joined:
    Feb 23, 2010
    #6
    Thanks.

    I've just created a test image of that resolution and syncing now to see if the iPad can resolve pixels at that size.

    Update :)

    Well, I've just tried the resolution you suggested and indeed when zoomed in I can see the individual pixels I created at that res.

    I also tried 2048 x 1536 (double the screen res) and that appears to work well and resolve (just) individual pixels also, plus it has the benefit of being full screen when normal viewing.

    May I ask how you came up with that resolution?
     
  7. b.c. macrumors 6502

    Joined:
    Nov 5, 2008
    #7
    you're welcome :)

    here's what I did to confirm the resolution: I synced several albums of 10Mpixel photos in my iPhoto library to my iPad via iTunes (selected some albums in the iTunes photos tab). Originals were about 3~4Mbytes in size, 3888x2592 resolution

    on the iPad, I went to the Photos app, selected a photo to view it, then did a tap-hold to Copy the photo. then in Mail, pasted the photo into a new message and mailed to myself. then verified attachment image size back on my Mac after receiving the email.

    Note: copy/paste in this manner copies the full size image. Mailing a photo using the "email to" button in the Photos app sends a reduced size version

    by the way, I more recently found an article also confirming this 2304x1536 resolution for originals of higher resolution and >1MB filesize when synced via iTunes to iPad:

    http://thedigitalstory.com/2010/04/will_the_ipad_squish.html
     
  8. Piggie thread starter macrumors G3

    Piggie

    Joined:
    Feb 23, 2010
    #8
    Thanks for that.

    I'm still very puzzled about this apparent size.

    Given the screen is 1024x768

    One could think it was perhaps a natural idea to internally double this screen size for the main maximum image storage size, so when zoomed out to 1:1 size the image would correctly fit the screen.

    1024x768 times 2 = 2048x1536

    Quite how they decided on 2304x1536 is a bit beyond me, unless they are saying that the extra width is there as it matches the aspect ratio of a digital photo better than the aspect ratio of the iPad's screen.

    Do you think this is what it is?

    If I photoshop a large file, then I would crop it and resize to 2304x1536 so I get the max quality possible.

    Only a shame then that it gives me black borders when viewing
     
  9. b.c. macrumors 6502

    Joined:
    Nov 5, 2008
    #9
    I think the reason is they are simply maintaining the aspect ratio of the original photo. a lot of DSLR cameras have sensors with 3:2 aspect ratio, same as that of a 4x6 photographic print. My original test was using a 10Mpixel image from a DSLR (EOS 40D) with 3:2 aspect ratio, 3888x2592

    on the other hand, a lot of compact cameras (and some DSLRs) have 4:3 aspect ratio - same as the 1024x768 iPad display

    your question got me thinking about this, so I did a further test, this time with an image from a 12Mpixel compact camera (Canon SD960IS) which has a 4:3 aspect ratio image - resolution 3264x2448

    this time iTunes resizes the image to 2048x1536 (!) These photos will fill the iPad display perfectly, no narrow black borders.


    so my conclusion now is a bit different than before:

    it seems when syncing photos from iTunes/iPhoto to the iPad
    - large images are resized to 1536 pixels on their shortest side, and
    - original aspect ratio is preserved in the scaled-down image for iPad

    meaning 2304x1536 (3:2) or 2048x1536 (4:3)

    this gives at least 2x zoom possible on the iPad screen.
     
  10. Piggie thread starter macrumors G3

    Piggie

    Joined:
    Feb 23, 2010
    #10
    Excellent work..........

    So, from a Photoshop point of view:

    If you can, crop the image to a 4:3 ratio to give you 2x screen res (2048x1536) this will give you perfect fit and maximum quality.

    If you have a picture that wider than that (landscape) then crop/resize your image in photoshop to be 2304 pixels wide (by whatever height it is)

    If you have a narrow photo (tall building) then resize to 1536 pixels tall and whatever width the photo is.

    Agreed?

    :)
     
  11. b.c. macrumors 6502

    Joined:
    Nov 5, 2008
    #11
    BTW, maybe obvious but above discussion about automatic resizing applies when you are using iTunes to sync the photos to your iPod.

    if you import your photos directly to the iPad - e.g. using the Camera Connection Kit - then there is NO resizing done to your photos, they are stored in the iPad in full resolution.
     
  12. Piggie thread starter macrumors G3

    Piggie

    Joined:
    Feb 23, 2010
    #12
    Interesting point.

    Yes, for my needs I shall only be using iTunes but good to hear what you say. I do have one query just out of interest about your point.

    What about compression and formats when importing photos?

    On my dslr I always shoot in Nikon raw format which are of course large files, but give me maximum quality and adjustment potential in Photoshop.

    How does the iPad deal with this?

    Not that I ever see myself doing so as I regard the iPad as a device to display photos I have already edited for display on it.
     
  13. b.c. macrumors 6502

    Joined:
    Nov 5, 2008
    #13
    using iPhoto/iTunes to sync RAW files - iTunes converts the RAWs and just the optimized JPEG files are downloaded to your iPad. the iPad never receives the actual RAW files transferring photos this way. Whether JPEG or RAW, I'm pretty sure there's some compression going on in iTunes sync, but I don't know the details.

    using the Camera Connection Kit, you can load RAW files from your camera into your iPad. Same as with JPEGs loaded this way, the original files are not converted/modified by the iPad, and originals can be downloaded later to your computer.

    if I recall correctly, the embedded JPEG with the RAW (if any) is used for displaying on the iPad, otherwise the iPad creates a JPEG preview from the RAW - I'd guess it would be 2304x1536 or something like that. I've not played around with this much, other than to confirm that I can load RAW onto the iPad and get them back unmodified.

    if you shoot RAW+JPEG, then each photo results in 2 files loaded onto the iPad when using the CCK.

    to get the files off the iPad, you can use Image Capture app on your Mac (or iPhoto) to download the original RAW and/or JPEG files from the iPad.

    p.s. I had great hopes of using my 64GB iPad as a photo storage device while traveling (replacing my existing Epson P-2000). Although it can serve this basic function using the CCK, there's a simple yet serious deficiency in the current Photo app that makes this impractical...

    it's impossible to create a new album in the iPad Photos app! - this means if I shoot hundreds/thousands of photos over several days and upload to iPad, they can only live in one single album (the "All Imported" album). There's no way to organize photos as they are shot, by "roll" or day or event, which is what I do now on the P-2000.

    Hopefully a future update to the iPad software will add this simple function to add albums and move/sort photos
     

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