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jdecosta

macrumors member
Original poster
Feb 16, 2012
84
4
I have an iPad Air and a iPhone 5. Both have the same selection of pictures sync'd in iTunes. My iPad Air is showing 17.38 gigs with 5740 pictures. My iPhone 5 has 7.77 gigs and 5740 pictures.

So here is the question. Why is my iPad showing/using more storage then my iPhone even with the exact same pictures on both devices?
 

Night Spring

macrumors G5
Jul 17, 2008
14,530
7,712
iTunes compresses pictures when syncing them to iOS devices. It must compress them more when transferring to an iPhone. Which makes sense, because iPhone screen is smaller.
 

BJMRamage

macrumors 68030
Oct 2, 2007
2,708
1,229
the above is correct.

it is based on screen res/size/device for the size of the image.
 

jdecosta

macrumors member
Original poster
Feb 16, 2012
84
4
Thanks for the replies, that what I thought just wanted confirmation.
 

ApfelKuchen

macrumors 601
Aug 28, 2012
4,334
3,010
Between the coasts
It may be splitting hairs, but data compression is a hot-button issue for me...

What happens, in my experience, is that iCloud Photo Stream resizes the images, in sizes optimized to the resolution of the device's screen. Increasing "compression" implies returning a lower-quality (more aggressively-processed) JPG, and that, apparently, is not what's happening. (I could test this empirically, but time is short today.)

While in both cases, data is being thrown out, in resizing the effect is limited to adjoining pixels. In the case of aggressive JPG compression, the effect can range far beyond the immediate region.

One of the most obvious examples of this is in sunset photos, where aggressive data compression can result in a series of concentric bands, like an archery target - many pixels across a large area are very close in value, so many of them will be averaged to a single value.

While Apple is not explicit about whether it's resizing or resorting to heavier compression in http://support.apple.com/kb/HT4486 , "device-optimized resolution" strongly implies resizing, rather than greater compression.

What resolution are My Photo Stream photos?

On a Mac or PC, your photos are downloaded and stored in full resolution. On iPhone, iPad, iPod touch, and Apple TV, your Photo Stream photos are delivered in a device-optimized resolution that speeds downloads and saves storage space. Dimensions will vary, but an optimized version of a photo taken by a standard point-and-shoot camera will have a 2048 x 1536 pixel resolution when pushed to your devices. Panoramic photos can be up to 5400 pixels wide.
 

Night Spring

macrumors G5
Jul 17, 2008
14,530
7,712
It may be splitting hairs, but data compression is a hot-button issue for me...

What happens, in my experience, is that iCloud Photo Stream resizes the images, in sizes optimized to the resolution of the device's screen. Increasing "compression" implies returning a lower-quality (more aggressively-processed) JPG, and that, apparently, is not what's happening. (I could test this empirically, but time is short today.)

I believe you are right. Now that you brought it up, I remember there have been cases where people reported the storage size for their pictures *increasing* when synced to an iOS device compared to what they had on their computer, presumably because the resizing process resulted in larger file sizes.
 
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