The Truth About Resolution

Discussion in 'Digital Photography' started by Frank ess, Nov 27, 2007.

  1. Frank ess

    Frank ess Guest

    Frank ess, Nov 27, 2007
    #1
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  2. Frank ess

    John Navas Guest

    On Tue, 27 Nov 2007 10:43:35 -0800, "Frank ess" <>
    wrote in <>:

    >From Creatve Pro:
    >http://www.creativepro.com/story/howto/25527.html?cprose=daily


    As inaccurate as it is poorly written (and a sad commentary on
    iStockphoto.com):

    The Truth About Resolution

    Whenever an article proclaims "truth", baloney is sure to follow!

    When I became a pixel pusher years ago,

    2? 3?

    one of the toughest concepts
    to wrap my brain around was that of image resolution:

    And now she's an expert. :)

    I know better now, but many professional designers don't. They buy a
    high-quality photo from a stock agency, open it in Photoshop, and
    black out with rage when they see "resolution = 72" in the Image Size
    dialog. An irate call to customer service usually ensues, followed by
    an embarrassing explanation of Resolution 101 by someone half their
    age. ...

    Now we know how old she is.

    The Dark Art of Upsampling.

    Be afraid, be very afraid! :)

    The resolution measurement dictates how closely the pixels are packed
    together. Increasing an image's resolution means the pixels will be
    packed together more tightly, resulting in a smaller physical size,

    Other way around, but who's keeping track.

    but generating a smoother, higher quality print. Lowering an image's
    resolution means loosening the pixels, resulting in a larger physical
    image size, but generating a blocky, lower quality print.

    Sounds like slutty pixels to me! :)

    In fact any decent current printer driver does a good job of upsampling
    before printing.

    Think of the resolution measurement as density. For example, the
    tighter a substance is packed, the denser it is and the less surface
    area it takes up (like brown sugar). The more loosely a substance is
    packed, the more surface area it consumes and it becomes less dense.

    Are we talking crack or digital images? :)

    Because our eyes can only process so much information, a 72 ppi image
    onscreen looks identical to a 600 ppi image onscreen. ...

    Only if you have a crappy monitor or are legally blind.

    This gorgeous photo (courtesy of iStockphoto.com/Lisa Gagne) is
    measured at 72 ppi. Does that mean it's a low-quality image?
    Negatory, good buddy.

    She's my buddy? Does that mean what I think it does? :)

    Evil upsampling method #1: Open the Image Size dialog in Photoshop,
    take a deep breath, and leave the Resample Image box checked. (I
    realize I just told you not to do this, but bear with me.) Choose
    Bicubic Smoother from the pop-up menu to its right and change the
    document dimension pop-up menus to Percent. Enter 110% in the width
    box and press OK (Figure 3). Repeat this process as many times as
    necessary to enlarge the image. For some reason, adding data 10% at a
    time doesn't cause a huge amount of quality loss. Do resist the urge
    to increase the size more than 10% at a time, unless you want that
    chunky look.

    Stairstep interpolation is actually a bad idea. Bicubic Smoother works
    best in a single step.

    Evil upsampling method #2: Buy a plug-in, such as Genuine Fractals by
    onOne Software, Blow Up by Alien Skin, or PhotoZoom Pro 2 by
    BenVista. They pull off some serious voodoo and somehow manage to
    increase pixel data without totally destroying the image.

    As my own tests show ("Adobe Bicubic Smoother upsize vs Genuine
    Fractals"), there is very little difference between Bicubic Smoother and
    Genuine Fractals in large upsizing, and none at all in modest upsizing.

    I Wouldn't Lie to You

    When someone says "I Wouldn't Lie to You" you can be sure they're about
    to lie to you. Think used car salesperson. :)

    Resolution doesn't mean squat until that image is headed for a
    printer. ...

    And not even then, since the printer driver will upsample for you.

    Lesa Snider King is the chief evangelist of iStockphoto.com and
    founder of GraphicReporter.com.

    Yet she doesn't know how printer drivers work, thinks stairstep
    interpolation works, and doesn't know how well bicubic smoother works.
    Yikes!

    --
    Best regards,
    John Navas <http:/navasgroup.com>

    "Usenet is like a herd of performing elephants with diarrhea - massive,
    difficult to redirect, awe inspiring, entertaining, and a source of mind
    boggling amounts of excrement when you least expect it." --Gene Spafford
     
    John Navas, Nov 28, 2007
    #2
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  3. On Nov 27, 12:43 pm, "Frank ess" <> wrote:
    > From Creatve Pro:http://www.creativepro.com/story/howto/25527.html?cprose=daily


    I didn't think much of the article. When I first found rpd many years
    ago I got on a soapbox about resolution and didn't change very many
    minds.

    Problem is, there are MANY definitions of resolution. There is no
    final arbiter of English language.

    However, to my mind the best definition of resolution is what film
    photography used to use- an actual MEASURED value based on test
    charts.

    To me the number of pixels in the image is just that- a number!
    Theoretically there is a ratio of the resolution in each direction to
    the number of pixels in that direction. In a PERFECT camera with a
    perfect lens, the actual measured resolution would approach that
    number (about 0.7 times the number of pixels). But of course, no
    camera and no lens is perfect.
     
    Don Stauffer in Minnesota, Nov 28, 2007
    #3
  4. Frank ess

    Marvin Guest

    Don Stauffer in Minnesota wrote:
    > On Nov 27, 12:43 pm, "Frank ess" <> wrote:
    >> From Creatve Pro:http://www.creativepro.com/story/howto/25527.html?cprose=daily

    >
    > I didn't think much of the article. When I first found rpd many years
    > ago I got on a soapbox about resolution and didn't change very many
    > minds.
    >
    > Problem is, there are MANY definitions of resolution. There is no
    > final arbiter of English language.
    >
    > However, to my mind the best definition of resolution is what film
    > photography used to use- an actual MEASURED value based on test
    > charts.
    >
    > To me the number of pixels in the image is just that- a number!
    > Theoretically there is a ratio of the resolution in each direction to
    > the number of pixels in that direction. In a PERFECT camera with a
    > perfect lens, the actual measured resolution would approach that
    > number (about 0.7 times the number of pixels). But of course, no
    > camera and no lens is perfect.


    I agree, but there is confusion. See
    http://www.dpreview.com/learn/?/Glossary/Digital_Imaging/Resolution_01.htm/
    One part says resolution is "defined" by the number of
    pixels in the image. The next part brings up a chart used
    in film photography to determine the amount of detail that
    the camera can capture. The pixel count does control the
    maximum capability of the sensor to capture detail, but the
    capability of the camera also depends on the lens. Camera
    makers and sellers emphasize the pixel count because that is
    something most buyers think they understand, though it is
    often just in the sense that "more is better". The game is
    called "specsmanship".
     
    Marvin, Nov 28, 2007
    #4
  5. On Nov 28, 11:03 am, Marvin <> wrote:
    > Don Stauffer in Minnesota wrote:
    >
    >
    >
    > > On Nov 27, 12:43 pm, "Frank ess" <> wrote:
    > >> From Creatve Pro:http://www.creativepro.com/story/howto/25527.html?cprose=daily

    >
    > > I didn't think much of the article. When I first found rpd many years
    > > ago I got on a soapbox about resolution and didn't change very many
    > > minds.

    >
    > > Problem is, there are MANY definitions of resolution. There is no
    > > final arbiter of English language.

    >
    > > However, to my mind the best definition of resolution is what film
    > > photography used to use- an actual MEASURED value based on test
    > > charts.

    >
    > > To me the number of pixels in the image is just that- a number!
    > > Theoretically there is a ratio of the resolution in each direction to
    > > the number of pixels in that direction. In a PERFECT camera with a
    > > perfect lens, the actual measured resolution would approach that
    > > number (about 0.7 times the number of pixels). But of course, no
    > > camera and no lens is perfect.

    >
    > I agree, but there is confusion. Seehttp://www.dpreview.com/learn/?/Glossary/Digital_Imaging/Resolution_0...
    > One part says resolution is "defined" by the number of
    > pixels in the image. The next part brings up a chart used
    > in film photography to determine the amount of detail that
    > the camera can capture. The pixel count does control the
    > maximum capability of the sensor to capture detail, but the
    > capability of the camera also depends on the lens. Camera
    > makers and sellers emphasize the pixel count because that is
    > something most buyers think they understand, though it is
    > often just in the sense that "more is better". The game is
    > called "specsmanship".


    I agree. But the problem is that ANYONE can create a definition. The
    part that reads "resolution is defined by" is really meaningless.
    That can merely be HIS definition. Personally I find the science of
    film imaging to be far more consistant than that of digital, because
    there because the professional societies dealing with film photography
    for many decades did a good job, and the photo industry in those days
    was not as likely to attempt that specsmanship game, like they do now.

    Also, in the early days photography was dominated by really serious
    people. It wasn't until well after Eastman and his Kodaks that it
    became a consumer product.

    On the other hand, the drafts of the ISO spec on digital camera
    resolution was very good. Unfortunately, getting a current version
    requires spending bucks. I retired before the draft was finalized, and
    don't want to spend my own money just to see the spec. But as I say,
    the draft spec anyway was pretty good, but as far as I know, no
    advertiser uses ISO resolution in ads.
     
    Don Stauffer in Minnesota, Nov 29, 2007
    #5
  6. Frank ess

    Marvin Guest

    Don Stauffer in Minnesota wrote:
    <snip>
    > I agree. But the problem is that ANYONE can create a definition. The
    > part that reads "resolution is defined by" is really meaningless.
    > That can merely be HIS definition. Personally I find the science of
    > film imaging to be far more consistant than that of digital, because
    > there because the professional societies dealing with film photography
    > for many decades did a good job, and the photo industry in those days
    > was not as likely to attempt that specsmanship game, like they do now.
    >
    > Also, in the early days photography was dominated by really serious
    > people. It wasn't until well after Eastman and his Kodaks that it
    > became a consumer product.


    Kodak dominated film commercially, and they set up a
    research lab early on. That lab dominated the technical
    aspects of photo films, including terminology. It is
    similar to the way that Microsoft has dominated conventions
    in computer programming. Everyone else's document creation
    software has to be able to open Word files. All camera
    makers had to make products that accepted Kodak's films.

    >
    > On the other hand, the drafts of the ISO spec on digital camera
    > resolution was very good. Unfortunately, getting a current version
    > requires spending bucks. I retired before the draft was finalized, and
    > don't want to spend my own money just to see the spec. But as I say,
    > the draft spec anyway was pretty good, but as far as I know, no
    > advertiser uses ISO resolution in ads.
    >


    Few people seem to have any idea what ISO ratings mean in
    photography, or - for that matter - what ISO is. Sex sells
    cars; pixel counts sell digicams.
     
    Marvin, Nov 29, 2007
    #6
  7. On Nov 29, 11:13 am, Marvin <> wrote:
    >
    > Few people seem to have any idea what ISO ratings mean in
    > photography, or - for that matter - what ISO is. Sex sells
    > cars; pixel counts sell digicams.


    I was referring to the resolution spec, not the speed spec.

    I can remember early high fi days, people did sort of fall into line
    on defining bandpass, even in absence of a trade or professional group
    spec.

    On the other hand, I don't really feel TOO upset about the modern
    trend, since pixel count is certainly one of the main drivers of
    measured resolution.
     
    Don Stauffer in Minnesota, Nov 30, 2007
    #7
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