Is this a camera fault at wide angle?

Discussion in 'UK Photography' started by BigMac, May 7, 2004.

  1. BigMac

    BigMac Guest

    Hi

    I have a new Pentax Optio S4 and have just taken it out in anger for the
    first time. I wonder if the experts on this group would give me an opinion
    on something.

    Shooting down at Lulworth Cove down in Dorset I've noticed that all my shots
    have a darkening across the top corners of the shot, but only when taken at
    the widest angle of zoom.

    I don't think this NG takes file attachments, but you can see a sample at
    http://www.geocities.com/inkbm/ResizeofIMGP0214.JPG (145kb)

    Can this be considered a limitation on a £280 camera or would it be worth
    taking back?

    Thanks

    BigMac
     
    BigMac, May 7, 2004
    #1
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  2. BigMac

    mark Dunn Guest

    This is vignetting, the lens barrel casting a shadow on the film. It used to
    be, and still is, a feature of cheap lenses but can affect ther short end of
    a zoom, as you have found out. Probably not a 'fault' as such, but I would
    take it back for a refund and try another make. A camera that is fit for its
    purpose does not take defective photographs.
     
    mark Dunn, May 7, 2004
    #2
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  3. BigMac

    BigMac Guest

    thanks Mark, I might just do that
    I looked up vignetting, new word to me, the New Shorter Oxford English
    dictionary defines as

    vignetting n. <unknown>(a) rare = VIGNETTE n. 2; (b) the action or process
    of producing vignettes, esp. in photography;
    (c) Optics a darkening or loss of the periphery of an image, as a result of
    the blocking of some off-axis rays during their passage through the optical
    system:

    BigMac
     
    BigMac, May 7, 2004
    #3
  4. BigMac

    mark Dunn Guest

    You are probably expected to live with it, but I wouldn't.
     
    mark Dunn, May 7, 2004
    #4
  5. ----------

    I guess you could argue that it IS a fault - but not a developed one,
    occurring after the camera was first placed into use which would become a
    warrantee issue. It might properly be described, however, as a "design
    fault" and based on the Consumer Protection Act you could argue exactly as
    you suggest..."A camera that is fit for its purpose does not take defective
    photographs." at least to the extent of demanding a full refund from the
    retailer.

    Keep in mind that they will declare themselves not to be at fault, or liable
    for the refund or a replacement unit, and, they will try to refer you to the
    manufacturer under the warrantee but in British law it is the retailer that
    carries the can initially, vis a vis their customer, on "defective goods".

    Journalist
     
    Journalist-North, May 7, 2004
    #5
  6. It seemed to me, on looking at your picture (which is very nice, by the
    way) that the amount of vignetting was not excessive for the wide end of
    a zoom lens. I have seen worse. BTW, it is not only wide lenses which
    show this, I used to have a 100-300 zoom which showed similar vignetting
    at the long end.

    Some people actually like the effect, considering it to "hold in" the
    composition - many B&W printers, for example, will deliberately print in
    the upper corners to darken them a little.

    The other factor to be aware of is that if you use a polarising filter
    then blue sky will often acquire a density gradient - the area at right
    angles to the sun becomes significantly darker than the area close to
    the sun or directly opposite it. I can't rule this out for your picture,
    as the top right corner seems just a little darker than the top left.
    The fact that the sky gets much lighter close to the sea is a different
    issue altogether, almost certainly an atmospheric affect and not
    vignetting. You can only tell for sure where there is a horizontal
    density gradient into a corner (and then, for the previously-mentioned
    reason, if you are not using a polariser).

    It's up to you, but I think you will just have to live with it - I very
    much doubt that the vignetting is out of spec, or that you will find
    other cameras of similar quality/price which do not show similar
    vignetting.
     
    David Littlewood, May 8, 2004
    #6
  7. I've not read all the correspondence on this, so I hope I'm not repeating
    what has already been said, but two thoughts:

    1) You mention the vignetting in the top corners. Is there also vignetting
    in the bottom corners? If there is, it is definately a fault in this
    particular lens.

    2) Do you keep a filter (e.g a UV or skylight) on the lens to protect it?
    If so, it could be the filter mount which is causing the vignetting.

    Regards,
    Andrew
     
    andrew.stolworthy, May 9, 2004
    #7
  8. BigMac

    Dave Guest


    Assuming that you use one, try taking a picture without the lenshood. If you
    don't get the problem, then you need a wide-angle lens lenshood!

    Dave
     
    Dave, May 10, 2004
    #8
  9. If there *isn't* it would definitely be a fault - the lens would be out
    of alignment. I suspect it isn't noticeable, that's all.
    Yes, I was going to ask that.

    Can I just say that *all*[1] wide angle lenses will exhibit some
    vignetting - it's a geometric thing. ( The focal length to the corners
    is longer than that to the centre, and since the lens does not present a
    greater aperture [indeed, most show less] the light is reduced.)

    The key question (and one the poster asked) is 'is it acceptable?'

    Are there any standards for lens design that specify this? ISTR a figure
    of 80% being regarded as very good, probably from a Leitz source of
    years ago, before aspheric components.

    Mike

    [1] Technically, AIUI, it may be possible to design a lens without
    'vignetting' but it would have to be a fixed focal length, and would
    exhibit an S-shaped light intensity measurement from centre to corner.
    But I am getting a long way out of my depth here.
    [The reply-to address is valid for 30 days from this posting]
    --
    Michael J Davis
    <><
    Some newsgroup contributors appear to have confused
    the meaning of "discussion" with "digression".
    <><
     
    Michael J Davis, May 11, 2004
    #9
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