8 Replies Latest reply: Aug 3, 2007 9:22 PM by Richard.Taylor
Ryoichi Level 1 Level 1 (5 points)
Dear Forum:
When I load my Canon 30D photos into Iphoto, I notice the file size is smaller than the file size of the exact same picture held in the initial folder outside of Iphoto. Does this mean that Iphoto further compresses the JPEG file into a smaller one (and thus reduce image quality) or is something else going on?
Thanks,
Steve

MacBook, Mac OS X (10.4.8)
  • Terence Devlin Level 10 Level 10 (135,030 points)
    Ryoichi

    Welcome to the Apple Discussions.

    iPhoto does not compress or otherwise alter pics on import. What it does is store the original file in the Originals Folder and create a thumbnail in the Data folder of the iPhoto Library Folder. These thumbs are used exclusively for display in the iPhoto Window.

    Where are you finding these smaller size files?

    Regards

    TD
  • Ryoichi Level 1 Level 1 (5 points)
    TD,

    Thanks for the quick reply.

    Let me give you an example of the reduction in file size.

    In my "Pictures" folder of my hard drive I have the original photos I transferred from my Canon 30D. IMG_4013 for example has a size of 3,667,287 bytes.
    I imported that file into Iphoto 6. Now, if I look into the "Originals" folder of the Iphoto Library folder, IMG_4013 now has a file size of 3,564,308 bytes. Not a huge difference, but what happened to the 102,979 bytes? I have a theory now that you said that Iphoto does not corrupt the image: I think Iphoto is stripping the file of the "Focus point information" because Iphoto does not allow the viewer to toggle on/off the nine-point focus points. With Canon's image browser you flip a switch and see the nine -focus points and determine what part of the picture was selected as a focus point.

    Does my theory hold or can you think of something else?

    Steve
  • QuickTimeKirk Level 9 Level 9 (51,130 points)
    JPEG image format and Mac OS have a few Finder "differences" but the copy from your camera to iPhoto are exactly as the camera recorded them.
    Mac OS uses a special resource fork that holds the icon preview (what you see when browsing a folder of images).
    This resource fork is the cause of the additional file size you notice.
  • Ryoichi Level 1 Level 1 (5 points)
    QuicktimeKirk,
    Thanks for the info!
    Steve
  • Craig Garrison1 Level 1 Level 1 (25 points)
    I saw this post and, while its not dealing exactly with what I'm trying to figure out, it does relate...

    I have a Kodak EasyShare DX7590 zoom
    digital camera (5 MP) and have been pleased with it. Recently, though, I've noticed that I can take more pictures at its highest resolution setting (5 MP) than I had before. Then, I've been noticting that the size (MB) of the pictures I've been importing into iPhoto are significantly smaller than what a 5 MP picture should be. I contacted Kodak and sent them three samples and they said that they read as 4.98 MP pictures.

    In the information section of iPhoto the size of the pictures are showing up as 2576 x 1932 but their file sizes are showing up as 681 KB, 1.1 MB, etc.

    I can't seem to find out what exactly is going on. I basically want to make sure that I am getting enough pixels in our pictures so that those that we want to enlarge to, say 8 x 10, will come out relatively OK.

    Thanks for any help.
  • Mike N. (nahyunil) Level 6 Level 6 (8,275 points)
    2576x1932 is basically 5MP.

    Since Jpeg is a compressed format, and the compression amount can vary, check your camera to see if it has quality settings in addition to the image size.

    For example, see if there are Fine/Standard mode settings
  • Craig Garrison1 Level 1 Level 1 (25 points)
    Thanks Mike. I did find that setting and switched it to fine, which more than doubled the file size of the picture.

    So, should I be concerned that the file sizes for these 5 MP photos is less than or around 1 MB or is it the 2576x1932 pixel size that is most important? For instance, will there be an appreciable difference in a 2576x1932 4x6 picture that is 840KB vs the same that is 1.8 MB?

    Thanks for your help,

    Craig
  • Richard.Taylor Level 4 Level 4 (2,060 points)
    The file size is a measure of the information stored in the picture. A 4x6 picture that is all black has much less information in it than a 4 x 6 that is a full color picture of your aunt and uncle so, even though they are the same size and have the same number of pixels, the more complex photo requires a larger file size.

    Pictures have lots of redunancy, so the file doesn't have to have one byte for every pixel. If there are 500 white pixels in a row, you don't have to record them all, you can just say "500 white." So pictures can be compressed quite a bit with absolutely no loss of information ( a lossless compression, like TIFF and PNG.)

    JPEG compresses even further by making assumptions about how people see and how they will look at a photograph. The camera (and photo editors) give you the choice of how much loss you're willing to accept; hence the fine/standard/etc. settings.

    So 5 megapixels of photo don't at all need to use 5 megabytes of information.