Disconnect Between HD File Size & PS's File Size

Discussion in 'Digital Photography' started by One4All, Sep 9, 2007.

  1. One4All

    One4All Guest

    I don't think this group is just about the capture side of digital
    photography (cameras, etc.). I think it's also about working with
    images after capture, so that's why I submit the following.

    I scanned a 6x6 cm. film chrome @ 3200 ppi, @16-bit depth, as a raw
    image file. Of course, the file size is huge: 269.4 MB. My Mac G5 w/
    2.5 GB of RAM handles it ok. I use Photoshop CS (Ver. 8.) I'm just
    giving some background to reduce irrelevant questions or comments.
    Actual file size is irrelevant to my question.

    Now. There's no discrepancy between the raw image's file size on the
    HD & what PS shows in Image Size. That's OK.

    The problem is with the master image file I created from this raw
    file. My HD info shows the master file to be 433.6 MB, but PS>Image
    Size shows it to be 185.8 MB. No layers, etc., are involved. I notice
    that if I multiply 185.8 by 3 (the three RGB channels), I get close to
    the 433.6 MB that is in the HD file.

    I don't understand what's going on. Why is my raw file size the same
    on the HD & in PS, while the master image file is 3X larger on the HD
    than in PS? Why is there no problem with one file, but there is with
    another? I did a Save As on the raw file before cropping & editing, so
    I didn't do anything to the raw file. So, with the cropping, at least,
    the master file should be *smaller* not *larger* than the raw file.

    Can anyone help me? If you need more info, let me know, as I need
    accurate info from my HD window prior to working on my images. I'm
    very uncomfortable with this discrepancy. There should be agreement
    between what my HD tells me & what PS tells me.
    One4All, Sep 9, 2007
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  2. One4All

    AnswerMan Guest

    This could be one of the many thousands of computational errors built-into
    PhotoShop due to its 16-bit math foundation. This limitation harkens way back to
    the mid 1990's and they've never changed it nor will they, PhotoShop is clearly
    and has always been last-century technology. I would suggest trying to find a
    better 32-bit editor, like PhotoLine 32 for the Mac. See if it reports the
    correct sizes. Don't worry about it not reading your RAW files, it uses a method
    that can read virtually all RAW file formats in existence, and some that are
    even undocumented-- special purpose RAW data formats used for scientific
    research purposes. Just be sure to set your work-space's default gamma in the
    setup options for RAW files to 1.70 for Macs before importing a RAW file. Then
    it imports them all just fine with the proper levels.
    AnswerMan, Sep 9, 2007
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  3. One4All

    Marty Fremen Guest

    What is the file type of this master image file? It may be that it contains
    data other than just the image. For instance, a .PSD file (photoshop native
    format) will typically contain an additional bitmap which is a composite
    snapshot of how the picture looks with all the layers combined, this alone
    could double the file size. (In photoshop's preferences you can choose
    whether to save such a bitmap or not.)

    It wasn't clear to me from what you said whether the master image file had
    been cropped so I'm not sure what to make of the difference between it and
    the raw. If you have cropped the image then this may account for the 185MB
    reported v. 269MB raw.

    As a general point, I don't think it's worth worrying about file sizes in
    MB except as concerns having enough disk space, and uncompressed image size
    in MB as shown by photoshop has absolutely no use at all IMHO. Although
    labs often talk about images which open out to such-and-such a number of
    megabytes, I've never found such information in any way useful or relevent
    and I don't know anyone outside of processing lab brochures who talks about
    images in terms of their uncompressed bitmap size. All it tells you is how
    big the file would be if you saved it as an uncompressed bitmap, which is a
    file format that almost no-one uses.

    The important data about an image is the height & width in pixels, and
    sometimes the colour depth (8, 24, or 48 bit). (When it comes to printing
    you also need to determine the resolution in ppi, but this isn't a figure
    that has any real meaning outside of the context of printing.)
    Marty Fremen, Sep 9, 2007
  4. One4All

    One4All Guest

    The raw file I refer to is not the RAW file recorded by a digital
    camera. I call it a raw file to distinguish it from the files I've
    edited, based on it. It's the file that I scanned at max. optical
    resolution and bit depth of the scanner, without any scanner color,
    etc., modification. It's a standard TIFF file.

    Thank you for suggesting an alternative image editor.
    One4All, Sep 10, 2007
  5. One4All

    Jon Bell Guest

    The Image Size dialog that you get when you choose "Image Size" from
    the "Image" menu shows the size in *pixels*, not *bytes*. In PS CS2
    it reads e.g. "Pixel Dimensions: 2.00M" (not MB!).
    That's what I would expect for an uncompressed TIFF file that has 8 bits
    (1 byte) per RGB color channel: 3 bytes per pixel.
    Jon Bell, Sep 10, 2007
  6. One4All

    flambe Guest

    Besides the likelihood that your file size is too big for practical use:
    What do you mean by master file?
    A pdf file usually balloons up depending on layers and other things.
    You also may have converted one file to a higher color bit depth, like 8 to
    16, hence the trebling of size?
    flambe, Sep 10, 2007
  7. One4All

    One4All Guest

    As I told AnswerMan, it's a standard TIFF file. It was scanned from a
    6x6 cm. chrome (slide), at max. resolution and bit depth of the
    scanner. I call it raw, but it's not the RAW format that comes from a
    digital camera. There is no data other than the image.
    Wait a minute. I'm talking about the master image discrepancy, not the
    raw, or original image discrepancy, because there is no discrepancy
    there. Reread my post. It's the master that's the problem.
    I'm not following you. In another thread in
    http://groups.google.com/group/comp.periphs.printers/topics?hl=en, a
    post told me resolution is not that big a deal for Epson printers, so
    I guess file size and resolution are irrelevant, anymore? :) There
    has to be some standard, or nearly so, to achieve an acceptable print
    at a given size from a given file size at a given resolution. As
    usual, I'm behind the technology.
    There, you have me. H & W in pixels means nothing to me (or it hasn't,
    until now) because I've been a film photographer all my life. Somehow,
    I've got to translate pixel dimensions in my head into print (inches)
    dimensions, which I've asked about in a separate thread in this
    newsgroup. I just can't project a x b pixel dimensions to 8 x 10, 11 x
    14, etc., print sizes.I just bought a Pentax K10d camera & hopefully
    I'll start getting my head around this new way of talking about image

    I must also tell you that I am not formatting my images for computer
    viewing or just 4x6 snapshot prints. I'm looking at formatting images
    for 11x14 or greater print output. File size, resolution, and print
    size have to figure in there.

    One4All, Sep 10, 2007
  8. One4All

    One4All Guest

    "Practical use" is a relative term. The use you may have for a file
    can be far different than the use I may have. Let's just say, with the
    large file, my options are open. RAM and disk space are irrelevant for
    me. If I need more of either, I'll buy more, because they are cheap
    compared to my need.

    By master file, I mean the edited file generated from the original
    file that was scanned. The master file is what will generate all other
    uses of the image. I erroneously called the original file a raw file,
    which confused some people, who thought I was talking about the RAW
    format in a digital camera.
    There are no layers, etc., in the master file. I checked for that, but
    you may have a point. Like I said, I cropped the original image to
    produce the master image, which should have resulted in a smaller file
    size. But, the file shows on my HD as an "Adobe Photoshop TIFF file."
    The original shows as a "TIFF document." I don't think the Adobe TIFF
    file is a .pdf file. Am I wrong?

    I did not upsample the original from 8-bit to 16-bit. Both the
    original and the master files are in 16-bit. BTW, 8-bit to 16-bit is
    double, not triple, the file size.
    One4All, Sep 10, 2007
  9. One4All

    One4All Guest

    Just want to let you all know I solved my "problem." I checked the
    Layers palette more closely & saw there was a Histogram (Adjustment?)
    Layer in addition to the Background Layer. I flattened the image, did
    a Save, and Voila! The HD file size and PS's file size are identical.
    It's surprising how much a single Layer can add to an image's file
    One4All, Sep 12, 2007
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