Lens test charts for digicams

Discussion in 'Digital Photography' started by Don Stauffer, Apr 11, 2006.

  1. Don Stauffer

    Don Stauffer Guest

    I still have a couple of old lens test charts from film camera days. But
    to use it with digital and convert to lines per picture width is a pain.
    Are there any available CHEAP lens testing charts aimed at digicams?
     
    Don Stauffer, Apr 11, 2006
    #1
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  2. On Tue, 11 Apr 2006 15:18:29 +0100, Don Stauffer wrote:

    > I still have a couple of old lens test charts from film camera days. But
    > to use it with digital and convert to lines per picture width is a pain.
    > Are there any available CHEAP lens testing charts aimed at digicams?


    ISO resolution chart

    http://www.graphics.cornell.edu/~westin/misc/res-chart.html

    Focus chart

    http://md.co.za/d70/chart.html


    Both charts can be downloaded and printed.
    --

    Gautam Majumdar

    Please send e-mails to
     
    Gautam Majumdar, Apr 11, 2006
    #2
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  3. Don Stauffer

    js Guest

    "Don Stauffer" <> wrote in message
    news:WUO_f.12$...
    >I still have a couple of old lens test charts from film camera days. But to
    >use it with digital and convert to lines per picture width is a pain.


    Aw, Don, the results will just depress you.
     
    js, Apr 11, 2006
    #3
  4. Don Stauffer

    Don Stauffer Guest

    Gautam Majumdar wrote:
    > On Tue, 11 Apr 2006 15:18:29 +0100, Don Stauffer wrote:
    >
    >
    >>I still have a couple of old lens test charts from film camera days. But
    >>to use it with digital and convert to lines per picture width is a pain.
    >> Are there any available CHEAP lens testing charts aimed at digicams?

    >
    >
    > ISO resolution chart
    >
    > http://www.graphics.cornell.edu/~westin/misc/res-chart.html
    >
    > Focus chart
    >
    > http://md.co.za/d70/chart.html
    >
    >
    > Both charts can be downloaded and printed.



    Wow! Thanks. The ISO chart is just what I was looking for. I had never
    seen a free site on it before, I had just looked at ISO's own site and
    sure didn't want to pay 93 bucks for it!
     
    Don Stauffer, Apr 12, 2006
    #4
  5. Don Stauffer

    Don Stauffer Guest

    js wrote:
    > "Don Stauffer" <> wrote in message
    > news:WUO_f.12$...
    >
    >>I still have a couple of old lens test charts from film camera days. But to
    >>use it with digital and convert to lines per picture width is a pain.

    >
    >
    > Aw, Don, the results will just depress you.
    >
    >


    Probably no more than the old tests I did on my film cameras. Actually,
    as one who put in a short period as a lens designer, I am amazed at how
    WELL modern lenses work. Especially the zoom ones. Sure, they are not
    as good as single focal length lenses, but a lot better than early zooms.
     
    Don Stauffer, Apr 12, 2006
    #5
  6. "Don Stauffer" <> wrote in message
    news:Uf7%f.7$...
    SNIP
    >> ISO resolution chart
    >>
    >> http://www.graphics.cornell.edu/~westin/misc/res-chart.html

    SNIP
    >
    > Wow! Thanks. The ISO chart is just what I was looking for. I had
    > never seen a free site on it before, I had just looked at ISO's own
    > site and sure didn't want to pay 93 bucks for it!


    A word of caution though...

    Most people don't use/interpret the chart elements as intended. The
    bi-tonal chart elements, e.g. the hyperbolic 9 bar elements, are not
    very suited for quantification of resolution of sampling systems like
    digicams. And the are not meant to, they're there just for a visual
    clue (and aliasing detection). The sharp edges of the elements also
    skew the quantification due to their high spatial frequency
    components.

    The accidental alignment of the vertical/horizontal elements will skew
    the results, and a fraction of millimetre offset will in that case
    change the result (especially if a camera uses a mild anti-aliasing
    filter). The chart is also mostly testing horizontal/vertical
    resolution which would give e.g. Fuji sensors a benefit due to their
    45 degree rotated sensor layout.

    Finally, the chart needs to be shot at fairly short distance, when
    most lenses are designed for longer distance performance.

    IMHO a much better target to shoot is a sinusoidal grating. To
    overcome the limitation of magnification factor dependency, I created
    a version that's insensitive to shooting distance and allows to
    measure at many rotation angles in a single shot. It also reveals lens
    aberrations and camera shake if present, and it is a test of your
    printer capabilities, which would go unnoticed when printing the ISO
    target.

    You can make your own target from the following files at home with a
    decent inkjet printer.
    For HP/Canon inkjet printers (3.8MB):
    <http://www.xs4all.nl/~bvdwolf/main/downloads/Jtf60cy-100mm_600ppi.gif>
    For Epson inkjet printers (5.3MB):
    <http://www.xs4all.nl/~bvdwolf/main/downloads/Jtf60cy-100mm_720ppi.gif>

    Print it at the indicated ppi without printer enhancements on glossy
    Photopaper which should produce a 100x100mm target, and shoot it with
    your (digi)cam from a (non-critical) distance like between 25-50x the
    focal length, or more. This will probably ensure that the target will
    'out-resolve' the capabilities of the lens, and thus easily those of
    the AA-filtered sensor.

    The resulting "blur"centre diameter is a measure of "on-sensor
    resolution" of the whole optical chain (lens+AA-filter+sensor), and
    can be quantified as cy/mm after calculating "(60/pi)/diameter". The
    diameter can be expressed as number of pixels multiplied by the pixel
    pitch.
    If you want to compare to different sized sensor arrays, all you need
    to do is relate it to physical sensor size, i.o.w. normalize
    magnification differences to same sized output.

    It will also reveal certain Raw converter issues (e.g. false-color
    aliasing artifacts) as it approaches the limiting resolution.

    Bart
     
    Bart van der Wolf, Apr 13, 2006
    #6
  7. Don Stauffer

    Don Stauffer Guest

    Bart van der Wolf wrote:

    > Finally, the chart needs to be shot at fairly short distance, when most
    > lenses are designed for longer distance performance.
    >


    But at any given focal length, in order to properly frame by format
    ratio, as shown on the chart, that limits the object distance to a fixed
    value, doesn't it?
     
    Don Stauffer, Apr 13, 2006
    #7
  8. "Don Stauffer" <> wrote in message
    news:b%s%f.10$...
    > Bart van der Wolf wrote:
    >
    >> Finally, the chart needs to be shot at fairly short distance, when
    >> most lenses are designed for longer distance performance.
    >>

    >
    > But at any given focal length, in order to properly frame by format
    > ratio, as shown on the chart, that limits the object distance to a
    > fixed value, doesn't it?


    Yes, and that is IMO a drawback for 'normal' focal lengths and more so
    for Wide-angles. One can of course produce a larger version to allow
    framing at a larger object distance, but the other drawbacks remain.

    Bart
     
    Bart van der Wolf, Apr 13, 2006
    #8
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