neutral color lenses vs. vivid/saturated ones

Discussion in 'Digital Photography' started by Moe, Jan 22, 2004.

  1. Moe

    Moe Guest

    Hello,

    I know there are at least a couple of properties to judge the quality
    of a lens: 1) sharpness 2) speed (light gulping capacity).

    When reading commentaries on lenses such as Canon's 50mm f/1.4, you
    hear folks praising it as having neutral/normal color (whatever
    "normal" means).

    When talking of other lenses, you might hear folks praising the
    saturated/vivid color reproduction..

    i wonder where this color "interpretation" came from when talking
    about lenses, isn't a lens a set of clear curved glass?

    it sounds to me that color reproduction is yet another property of the
    lens - though i've always thought that was a film
    property/responsiblity instead..

    To my beginner's eyes, i usually find myself happiest with vivid and
    sharp images (with a few exception of high art work, naturally done by
    someone other than myself).

    and shouldn't we be able to reproduce the effect of a vivid/saturated
    lens when using a neutral one by simply underexposing, say, half a
    stop or so?


    Thanks for your opinion..

    Moe
     
    Moe, Jan 22, 2004
    #1
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  2. Moe

    Bruce Murphy Guest

    It means that it doesn't cause a colour cast in the finished
    photograph. In this case, it's somewhat different to the rest of the
    Canon lenses which I believe tend to be cooler (bluer). Nikon lenses
    tend to be warmer.
    Probably a quite different type of review. Cheap nasty crap consumer
    lenses tend to have lots of low-quality elements which spread the
    light around as flare. This reduces the contrast of the image -- in
    the limit you'd eventually end up with a flat blur of a single
    colour. Presumably the reviewer (who is almost certainly a paid
    sympathiser) is talking about how much less contrast degrading flare
    this has compared to some other nasty cheap consumer lenses.
    Once the light has been conveyed to the film it becomes a film
    problem, yes. That it isn't entirely up to the film is obvious by
    people using filters, which are effectively lens modifiers.
    No. See above, the two colour reproduction comments are talking about
    quite different things and are consequently not comparable in this
    fashion.

    B>
     
    Bruce Murphy, Jan 22, 2004
    #2
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  3. Two reasons why lenses have "colour" characteristics.

    First, no glass, however good, will transmit 100% of the light hitting
    it. A given thickness, as in a lens element, might transmit 99 or 99.9%
    of it, but it won't be 100%. This transmittance factor will vary with
    the frequency (colour) of the light. Thus, especially in compound lenses
    with many elements (and don't forget, some zooms have 15 or more
    elements) there may be a small but noticeable colour cast, akin to using
    a weak filter.

    Second, there is the anti-reflective coating. Most of the lens - air
    surfaces need complex coatings to cut down reflections. A complex zoom
    without these would cause as much as 50% of the incident light scattered
    around by these reflections instead of forming an image (which reduces
    effective aperture of the lens, and dramatically reduces contrast in the
    image). These coatings are usually in several layers of different
    refractive index materials and are a fraction of a wavelength thick
    (i.e. very thin). These reduce reflections by interference effects
    (sorry, you'll have to look it up if you don't know about interference);
    this is also dependent to some extent on the frequency (colour) of the
    light. Thus different designs of coating will have slightly different
    colour curves.

    These two effects are (or should be) quite slight, and would probably
    only be noticeable to very critical workers using well-standardised
    techniques and processing, and even then only when using transparency
    film. Also, the good manufacturers take care to ensure that their range
    of lenses has consistency throughout the range.

    Critical users can see a difference between different manufacturer's
    ranges, and (much less often) within lens ranges. However, if you use
    colour negative film the colour balancing adjustments at the printing
    stage will swamp these small effects and I really don't think you would
    even detect them consistently.

    Even with transparency film, the different characteristics of the
    various types would probably be more noticeable than the colour
    rendition of the lenses themselves except in extreme cases.
    This is (as someone else said) almost certainly a contrast issue, not a
    colour rendition issue. The ability of lenses to transfer as much as
    possible of the contrast present in the scene is very important - at
    least as important as resolution. Here there is a very great visible
    difference between the best and worst of lenses, as anyone using (for
    example) Zeiss Contax G2 lenses will know (and I don't mean to exclude
    others, it's just that I can speak from experience here).
    This will have no effect whatever on the ability of the lens to transfer
    contrast. It will however prevent the film from blowing out in the
    highlights, and may give denser, more saturated colours. It may increase
    or reduce true contrast depending on scene and exposure. Contrast and
    density are of course two entirely different properties.
     
    David Littlewood, Jan 22, 2004
    #3
  4. Moe

    KBob Guest

    Here's an interesting URL by Robert Monaghan regarding lens
    coloration:
    http://medfmt.8k.com/mf/color.html
     
    KBob, Feb 9, 2004
    #4
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