Resolution question

Discussion in 'Digital Photography' started by wildbill54, Jan 9, 2004.

  1. wildbill54

    wildbill54 Guest

    I am scanning slides with a Minolta Dimage Scan Elite II. I have been
    saving my scans as .TIFF files thinking that as they are larger files I can
    enlarge them later on for better resolution prints. The other choices are
    JPEG or BMP. JPG files are smaller and I believe the image is compressed so
    the print size is limited and resolution suffers. BMP files are larger than
    TIFF files so I don't save my scans in that format.

    Is my choice to save my scans as TIFF files correct?

    Any help would be appreciated.

    Bill
    wildbill54, Jan 9, 2004
    #1
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  2. wildbill54

    Mark Herring Guest

    On Fri, 09 Jan 2004 04:51:37 GMT, "wildbill54" <>
    wrote:

    >I am scanning slides with a Minolta Dimage Scan Elite II. I have been
    >saving my scans as .TIFF files thinking that as they are larger files I can
    >enlarge them later on for better resolution prints. The other choices are
    >JPEG or BMP. JPG files are smaller and I believe the image is compressed so
    >the print size is limited and resolution suffers.


    Nope---JPEG compresses based on brightness (luminance) info. It does
    not reduce spatial resolution. Don't confuse file size with pixel
    count----- a 5Mpixel image uncompressed (eg a TIFF) will have
    15MBytes. (24 bits per pixel). JPG achieves compression by assigning
    fewre bits per pixel in areas where the values are fairly uniform.
    The image will still have 5 Mpixels
    > BMP files are larger than
    >TIFF files so I don't save my scans in that format.
    >
    >Is my choice to save my scans as TIFF files correct?


    ALWAYS save in the highest quality setting available--memeory is cheap
    >
    >Any help would be appreciated.
    >
    >Bill
    >


    **************************
    Mark Herring, Pasadena, Calif.
    Private e-mail: Just say no to "No".
    Mark Herring, Jan 9, 2004
    #2
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  3. wildbill54

    Mark Roberts Guest

    "wildbill54" <> wrote:

    >I am scanning slides with a Minolta Dimage Scan Elite II. I have been
    >saving my scans as .TIFF files thinking that as they are larger files I can
    >enlarge them later on for better resolution prints. The other choices are
    >JPEG or BMP. JPG files are smaller and I believe the image is compressed so
    >the print size is limited and resolution suffers.


    JPEG compression preserves luminance data for the most part, but
    sacrifices hue data to reduce file size. The actual number of output
    pixels doesn't change with increasing JPEG compression, but picture
    information does, so the effect on print size is similar.

    >Is my choice to save my scans as TIFF files correct?


    Basically, yes.

    --
    Mark Roberts
    Photography and writing
    www.robertstech.com
    Mark Roberts, Jan 9, 2004
    #3
  4. "wildbill54" <> writes:

    > I am scanning slides with a Minolta Dimage Scan Elite II. I have been
    > saving my scans as .TIFF files thinking that as they are larger files I can
    > enlarge them later on for better resolution prints. The other choices are
    > JPEG or BMP. JPG files are smaller and I believe the image is compressed so
    > the print size is limited and resolution suffers. BMP files are larger than
    > TIFF files so I don't save my scans in that format.
    >
    > Is my choice to save my scans as TIFF files correct?
    >
    > Any help would be appreciated.


    TIFF is the most conservative choice; no compression losses, a nice
    standard widely-supported format. If you can deal with the large file
    sizes, no need to look further.

    Archiving the scans in high-quality jpeg can also be tolerable. JPEG
    is a lossy compression format, so you don't get *quite* as good
    quality -- but you can get 5x compression even at the better quality
    levels, so that might be worth it to you, if you're having trouble
    with the tiff file sizes.

    No reason to consider BMP over TIFF.
    --
    David Dyer-Bennet, <mailto:>, <http://www.dd-b.net/dd-b/>
    RKBA: <http://noguns-nomoney.com> <http://www.dd-b.net/carry/>
    Photos: <dd-b.lighthunters.net> Snapshots: <www.dd-b.net/dd-b/SnapshotAlbum/>
    Dragaera/Steven Brust: <http://dragaera.info/>
    David Dyer-Bennet, Jan 9, 2004
    #4
  5. wildbill54

    Don Stauffer Guest

    A key idea is to do any editing needed BEFORE saving as jpeg. Editing
    an image saved as jpeg, and then resaving it will do the compression
    again, and artifacts are much more likely to show up.

    Jpeg compression compresses colors and subtle shading, so if there is
    any color correction or contrast changes, be sure and do that before
    first jpeg save.

    David Dyer-Bennet wrote:
    >
    > "wildbill54" <> writes:
    >
    > > I am scanning slides with a Minolta Dimage Scan Elite II. I have been
    > > saving my scans as .TIFF files thinking that as they are larger files I can
    > > enlarge them later on for better resolution prints. The other choices are
    > > JPEG or BMP. JPG files are smaller and I believe the image is compressed so
    > > the print size is limited and resolution suffers. BMP files are larger than
    > > TIFF files so I don't save my scans in that format.
    > >
    > > Is my choice to save my scans as TIFF files correct?
    > >
    > > Any help would be appreciated.

    >
    > TIFF is the most conservative choice; no compression losses, a nice
    > standard widely-supported format. If you can deal with the large file
    > sizes, no need to look further.
    >
    > Archiving the scans in high-quality jpeg can also be tolerable. JPEG
    > is a lossy compression format, so you don't get *quite* as good
    > quality -- but you can get 5x compression even at the better quality
    > levels, so that might be worth it to you, if you're having trouble
    > with the tiff file sizes.
    >
    > No reason to consider BMP over TIFF.
    > --
    > David Dyer-Bennet, <mailto:>, <http://www.dd-b.net/dd-b/>
    > RKBA: <http://noguns-nomoney.com> <http://www.dd-b.net/carry/>
    > Photos: <dd-b.lighthunters.net> Snapshots: <www.dd-b.net/dd-b/SnapshotAlbum/>
    > Dragaera/Steven Brust: <http://dragaera.info/>


    --
    Don Stauffer in Minnesota

    webpage- http://www.usfamily.net/web/stauffer
    Don Stauffer, Jan 10, 2004
    #5
  6. wildbill54

    Brent Geery Guest

    On Sat, 10 Jan 2004 09:45:44 -0600, Don Stauffer
    <> wrote:

    > David Dyer-Bennet wrote:
    > >
    > > "wildbill54" <> writes:
    > >
    > > > I am scanning slides with a Minolta Dimage Scan Elite II. I have been
    > > > saving my scans as .TIFF files thinking that as they are larger files I can
    > > > enlarge them later on for better resolution prints. The other choices are
    > > > JPEG or BMP. JPG files are smaller and I believe the image is compressed so
    > > > the print size is limited and resolution suffers. BMP files are larger than
    > > > TIFF files so I don't save my scans in that format.
    > > >
    > > > Is my choice to save my scans as TIFF files correct?
    > > >
    > > > Any help would be appreciated.

    > >
    > > TIFF is the most conservative choice; no compression losses, a nice
    > > standard widely-supported format. If you can deal with the large file
    > > sizes, no need to look further.
    > >
    > > Archiving the scans in high-quality jpeg can also be tolerable. JPEG
    > > is a lossy compression format, so you don't get *quite* as good
    > > quality -- but you can get 5x compression even at the better quality
    > > levels, so that might be worth it to you, if you're having trouble
    > > with the tiff file sizes.
    > >
    > > No reason to consider BMP over TIFF.

    >
    > A key idea is to do any editing needed BEFORE saving as jpeg. Editing
    > an image saved as jpeg, and then resaving it will do the compression
    > again, and artifacts are much more likely to show up.
    >
    > Jpeg compression compresses colors and subtle shading, so if there is
    > any color correction or contrast changes, be sure and do that before
    > first jpeg save.


    Any advantage of TIFF vs PNG?

    --
    BRENT - The Usenet typo king. :)

    Fast Times At Ridgemont High Info http://www.FastTimesAtRidgemontHigh.org
    Voted #87 - American Film Institute's Top 100 Funniest American Films
    Brent Geery, Feb 24, 2004
    #6
  7. Archival storage format [Was: Resolution question]

    Brent Geery <> writes:
    > Any advantage of TIFF vs PNG?


    Both supports lossless storage of 8 or 16 bit/channel image data.

    TIFF - Tag(ged) Image File Format. This is a proprietay format (it is
    owned by Adobe) that first appeared in 1986. It is - at least in
    principle - a very flexible format (more than 300 subtypes are
    currently defined) that can be lossless or lossy. In practice, TIFF
    is used almost exclusively for uncompressed, lossless image storage,
    and as such it is widely supported. In addition to archical storage
    of 24 or 48 bit/pixel RGB data, a major use of TIFF is as an
    interchange format for CMYK data the graphics industry. PhotoShop
    allows users to use a lossless compression algorithm called LZW to
    compress the data, or even the lossy JPEG algorithm, but these
    variations on the TIFF theme has limited support. TIFF can contain
    EXIF or IPTC metadata.

    PNG - Portable Network Graphics (or PNG's Not Gif). This is a
    lossless, compressed format. It is documented in RFC 2083 (published
    in January 1997). It was originally designed to be a GIF-replacement
    (because the LZW-patent made it difficult to use GIF in free
    software), but goes beyond that. PNG is better than GIF in most
    respects. It supports true colour with sample depths ranging from 1
    to 16 bits (i.e. up to 48 bit RGB), it also supports alpha channels
    (8 or 16 bit variable transparency), gamma correction (cross-platform
    control of image brightness), and two-dimensional interlacing (a
    method of progressive display). Unlike TIFF, the PNG specification
    leaves no room for implementors to pick and choose what features
    they'll support. A PNG image saved in one compliant application is
    readable in any other PNG-compliant application. PNG supports three
    main image types: true colour (which can be 24 bit or 48 bit RGB), 16
    bit grayscale and indexed-colour (256 colours, i.e. 8 bits, indexing
    a 24 bit palette). JPEG only supports the first two, GIF only the
    third. Note that if you use 256 colours or less, a well-behaved PNG
    application should store the image with an 8-bit palette, resulting in
    a smaller file-size than if you used GIF. Use 257 colours, and PNG
    shifts to 24 bit RGB, and the file triples in size. PMG is suitable
    for web use, and may replace TIFF for long time storage of RGB data.
    However, it does not support CMYK, and metadata support is sketchy
    (there is a group working on EXIF-support, but nothing is yet
    approved).

    To summarize:

    TIFF:
    Pro: Widely supported, embedded metadata.
    Con: Propritary, complex, non-standard subtypes.

    PMG:
    Pro: Compact files, open and well-defined (RFC 2083).
    Con: No emedded metadata, not universally supported.

    Personally, I am moving from TIFF to PNG for archival storage.
    I think there is only a matter of time before PNG is just as
    widely supported by applicatons as TIFF. I also expect the
    metadata issue to be resolved at one point.

    --
    - gisle hannemyr [ gisle{at}hannemyr.no - http://folk.uio.no/gisle/ ]
    ========================================================================
    «To live outside the law, you must be honest.» (Bob Dylan)
    Gisle Hannemyr, Feb 24, 2004
    #7
  8. wildbill54

    John Navas Guest

    [POSTED TO rec.photo.digital - REPLY ON USENET PLEASE]

    In <> on Tue, 24 Feb 2004 01:24:30
    -0800, Brent Geery <> wrote:

    >Any advantage of TIFF vs PNG?


    PNG is much newer, better specified, and more capable, but TIFF is still more
    universal.

    --
    Best regards,
    John Navas
    [PLEASE NOTE: Ads belong *only* in rec.photo.marketplace.digital, as per
    <http://bobatkins.photo.net/info/charter.htm> <http://rpdfaq.50megs.com/>]
    John Navas, Feb 24, 2004
    #8
  9. wildbill54

    PR Guest

    On Tue, 24 Feb 2004 01:24:30 -0800, Brent Geery
    <> wrote:

    >
    >Any advantage of TIFF vs PNG?


    PNG (Portable Network Graphics) was designed for the WEB,
    so if you ever intend to put the photos directly on the
    WEB PNG might be better.

    PNG is the newer standard. I save my images in PNG.


    --
    http://www.ransen.com/
    Repligator - Easy graphics effects
    Gliftic - Easy decorative tilings
    PR, Feb 25, 2004
    #9
  10. Re: Archival storage format [Was: Resolution question]

    Gisle Hannemyr <> wrote in message news:<>...
    > Brent Geery <> writes:
    > > Any advantage of TIFF vs PNG?

    > PNG: ...metadata support is sketchy
    > (there is a group working on EXIF-support, but nothing is yet
    > approved).
    >
    > ...I also expect the
    > metadata issue to be resolved at one point.


    There hasn't been much activity within the PNG Development Group for
    several years about EXIF support. The current proposal is dated
    December 2000 (see http://pmt.sourceforge.net/exif)

    This is just one of three methods we have discussed. The simplest is to
    just dump the raw EXIF data, in the same format as in TIFF or JPEG,
    into a special-purpose ("eXIF") chunk. Another is to hex-encode
    the raw EXIF data and store it in a PNG "zTXt" chunk -- this is what
    ImageMagick has been doing to preserve the EXIF (and IPTC) data. Both of
    these methods are easy to implement, and serve the purpose of preserving
    the data, but they have to rely on other software to interpret the data.
    Frequently the resulting chunks are quite large due to the presence of
    and EXIF thumbnail within the data. ImageMagick users are continually
    surprised when they convert a large JPEG to a small thumbnail and get
    a 30-kbyte file when they were expecting 2 or 3 kbytes.

    The proposal referenced above is more complicated. It converts the
    EXIF data to human-readable form and stores it in a series of
    keywords and values in a PNG tEXt or zTXt chunk, and abandons any
    embedded thumbnail.

    Glenn
    Glenn Randers-Pehrson, Feb 25, 2004
    #10
  11. wildbill54

    bob Guest

    (PR) wrote in news::

    > On Tue, 24 Feb 2004 01:24:30 -0800, Brent Geery
    > <> wrote:
    >
    >>
    >>Any advantage of TIFF vs PNG?

    >
    > PNG (Portable Network Graphics) was designed for the WEB,
    > so if you ever intend to put the photos directly on the
    > WEB PNG might be better.
    >
    > PNG is the newer standard. I save my images in PNG.


    Being the newer standard, it isn't as widly adopted yet, either. Adobe
    Acrobat, for instance, doesn't read .png.

    Bob


    --
    remove the backwards "SPAM" to reply.
    bob, Feb 25, 2004
    #11
  12. wildbill54

    Brent Geery Guest

    Re: Archival storage format [Was: Resolution question]

    On Tue, 24 Feb 2004 13:02:05 +0100, Gisle Hannemyr
    <> wrote:

    > Brent Geery <> writes:
    > > Any advantage of TIFF vs PNG?


    ....snip...

    > To summarize:
    >
    > TIFF:
    > Pro: Widely supported, embedded metadata.
    > Con: Propritary, complex, non-standard subtypes.
    >
    > PMG:
    > Pro: Compact files, open and well-defined (RFC 2083).
    > Con: No emedded metadata, not universally supported.
    >
    > Personally, I am moving from TIFF to PNG for archival storage.
    > I think there is only a matter of time before PNG is just as
    > widely supported by applicatons as TIFF. I also expect the
    > metadata issue to be resolved at one point.


    Thanks for the great info.

    So, looks like the lack of embedded metadata is the only real con for
    PNG (a format I really like,) as a format for archiving digital
    photos. I suppose, simply saving a TXT file with this information
    will serve, at least until they finally get the issue settled.

    What gets me upset, is we still have cameras using uncompressed TIFF
    (due o the compression patents) and not including PNG support. They
    could go with a proprietary/non-standard system for the metadata, like
    they do with TIFF, until the issue is standardized for PNG.

    --
    BRENT - The Usenet typo king. :)

    Fast Times At Ridgemont High Info http://www.FastTimesAtRidgemontHigh.org
    Voted #87 - American Film Institute's Top 100 Funniest American Films
    Brent Geery, Feb 26, 2004
    #12
  13. Re: Archival storage format [Was: Resolution question]

    > > PNG:
    > > Pro: Compact files, open and well-defined (RFC 2083).
    > > Con: No emedded metadata, not universally supported.


    PNG does allow the saving of text strings:

    Author, Description, Software & Title

    so there is scope for metadata, although not in the format way of an EXIF
    header, for example.

    Cheers,
    David
    David J Taylor, Feb 26, 2004
    #13
  14. wildbill54

    John Navas Guest

    Re: Archival storage format [Was: Resolution question]

    [POSTED TO rec.photo.digital - REPLY ON USENET PLEASE]

    In <> on Thu, 26 Feb 2004 00:05:55
    -0800, Brent Geery <> wrote:

    >What gets me upset, is we still have cameras using uncompressed TIFF
    >(due o the compression patents) ...


    That was only an issue for LZW compression, and is no longer an issue in the
    USA, since the USA patent expired in June 2003. (The Canadian and European
    patents remain in effect until July 2004.) But the bigger issue is that LZW
    compression doesn't work terribly well for raw 24-bit image data -- it can
    even increase file size. TIFF also supports Huffman encoding, but that's not
    effective either.

    --
    Best regards,
    John Navas
    [PLEASE NOTE: Ads belong *only* in rec.photo.marketplace.digital, as per
    <http://bobatkins.photo.net/info/charter.htm> <http://rpdfaq.50megs.com/>]
    John Navas, Feb 26, 2004
    #14
  15. Re: Archival storage format [Was: Resolution question]

    > That was only an issue for LZW compression, and is no longer an issue in
    the
    > USA, since the USA patent expired in June 2003. (The Canadian and

    European
    > patents remain in effect until July 2004.) But the bigger issue is that

    LZW
    > compression doesn't work terribly well for raw 24-bit image data -- it

    can
    > even increase file size. TIFF also supports Huffman encoding, but

    that's not
    > effective either.


    PNG compression should work more effectively as it is specifically
    designed for images. I haven't done a comparison, though.

    Cheers,
    David
    David J Taylor, Feb 26, 2004
    #15
  16. Re: Archival storage format [Was: Resolution question]

    David J Taylor writes:
    > John Navas wrote:


    >> That was only an issue for LZW compression, and is no longer an
    >> issue in the USA, since the USA patent expired in June 2003. (The
    >> Canadian and European patents remain in effect until July 2004.)
    >> But the bigger issue is that LZW compression doesn't work terribly
    >> well for raw 24-bit image data -- it can even increase file size.
    >> TIFF also supports Huffman encoding, but that's not effective
    >> either.


    > PNG compression should work more effectively as it is specifically
    > designed for images. I haven't done a comparison, though.


    For what it is worth, I've done some comparisons of different lossless
    (TIF, PNG, CRW) and lossy (JPG and GIF) file formats, summarized in
    the table below (you'll need to display it in a monospaced font for
    the columns to line up properly):

    =============================================================
    Format img#1 0.3 Mpx img#2 0.3 Mpx img#2 5.0 Mpx
    -------------------------------------------------------------
    TIF (uncomp.) 900 KB 124 % 911 KB 178 % 14.4 MB 208 %
    TIF (LZW) 945 KB 130 % 685 KB 134 % 8.20 MB 118 %
    PNG (PS7) 772 KB 106 % 568 KB 111 % 7.16 MB 103 %
    PNG (opt.) 727 KB 100 % 512 KB 100 % 6.92 MB 100 %
    CRW 4.95 MB 72 %
    JPG (12) 500 KB 69 % 316 KB 62 % 3,30 MB 48 %
    GIF 258 KB 35 % 172 KB 34 % 2.05 MB 30 %
    JPG (10 - max) 266 KB 37 % 139 KB 27 % 1.35 MB 20 %
    JPG (8 - high) 160 KB 22 % 81 KB 16 % 0.72 MB 10 %
    JPG (5 - med.) 103 KB 14 % 49 KB 10 % 0.37 MB 5 %
    JPG (0) 46 KB 6 % 16 KB 3 % 0.15 MB 2 %
    =============================================================

    The table shows abolute and relative file sizes of two images (img#2
    is shown in two different resolutions). The relative sizes is shown
    as a percentage of best PNG file size.

    What entails (at least for these images) is that PNG is more compact
    than TIFF. For some images, the saving may be dramatic (e.g. the
    5 Mpx version of #img#2 require less than half the disk space if
    stored as PNG when compared to uncompressed TIFF).

    More tests indicate that how much space you "waste" using TIFF (both
    uncompressed and LZW) varies a great deal from picture to picture -
    but PNG seems to be consistently more compact than TIFF.


    Details:

    img#1 is a foilage shot somebody posted on the Internet to demonstrate
    the effect that John Navas metions (that LZW-encoding may increase the
    file size). Unfortunately, that image was downsampled to 0.3 Mpx. I
    have not yet seen this occur with any of my own photographs, so - so
    far - I've not been able to reproduce the "LZW increases file size"-
    effect) in a full size image.

    img#2 is a randomly selected image (snapshot of my nephew), and I've
    included the data for both the full size (5 Mpx) and downsampled
    (0.3 Mpx) versions.

    The CRW (12 bit/channel) image is direct from camera (Canon PowerShot
    G5). All the derived format saved with Photoshop 7 in 8 bit/channel
    mode (24 bit RGB) - settings reflect Photoshop parameters and default
    settings, unless otherwise indicated. GIF and PNG are saved with no
    interlacing, GIF with selective palette, no dither and 256 colours.
    PNG is RGB (24 bit). PNG (PS7) is the "native" PNG produced by
    Photoshop 7. PNG (opt.) is the same file after postprocessing with
    PNGCrush to produce "best" compression. The number in after JPG in
    the format column is the paramter given to JPEG Options in Photoshop
    (a number between 0 and 12, where 0 gives the highest and 12 gives the
    least compression). JPG has been post-processed by JPG Cleaner, which
    removes roughly 20 KB of metadata added by PhotoShop.
    --
    - gisle hannemyr [ gisle{at}hannemyr.no - http://folk.uio.no/gisle/ ]
    ========================================================================
    «To live outside the law, you must be honest.» (Bob Dylan)
    Gisle Hannemyr, Feb 27, 2004
    #16
  17. Re: Archival storage format [Was: Resolution question]

    "Gisle Hannemyr" <> wrote in message
    news:...
    []
    > More tests indicate that how much space you "waste" using TIFF (both
    > uncompressed and LZW) varies a great deal from picture to picture -
    > but PNG seems to be consistently more compact than TIFF.


    Thanks for that, Gisle. It's as I expected, because of the mutli-line
    pixel-prediction optimisations built into PNG.

    Cheers,
    David
    David J Taylor, Feb 27, 2004
    #17
  18. Re: Archival storage format [Was: Resolution question]

    "David J Taylor" <-this-bit> wrote in message news:<THq%b.2949$>...
    > > That was only an issue for LZW compression, and is no longer an issue in

    > the
    > > USA, since the USA patent expired in June 2003. (The Canadian and

    > European
    > > patents remain in effect until July 2004.) But the bigger issue is that

    > LZW
    > > compression doesn't work terribly well for raw 24-bit image data -- it

    > can
    > > even increase file size. TIFF also supports Huffman encoding, but

    > that's not
    > > effective either.

    >
    > PNG compression should work more effectively as it is specifically
    > designed for images. I haven't done a comparison, though.


    PNG compression, while generally better than LZW, is actually most
    effective for "graphics" rather than "images". For natural images,
    the LOCO method has been found to be more effective and fast, too.
    It is available in MNG but not in PNG.

    Glenn
    Glenn Randers-Pehrson, Feb 27, 2004
    #18
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