Use of UV filters

Discussion in '35mm Cameras' started by Walter Banks, Sep 9, 2008.

  1. Walter Banks

    Walter Banks Guest

    I would like to see the pro's and cons of a UV filter or some other "lens protecting" glass on a lens.

    The small ghosts on very high contrast shots suggests that this is not a good idea. It has to degenerate even normal images.


    w..
     
    Walter Banks, Sep 9, 2008
    #1
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  2. Walter Banks

    Bruce Guest


    It sounds as though you have already drawn your own conclusions, so
    what would be the point in replying?
     
    Bruce, Sep 9, 2008
    #2
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  3. Walter Banks

    Ken Hart1 Guest

    Every piece of glass in the light path has some effect on the image.

    On the other hand, if something scratches the front of the lens, would you
    prefer that scratch on an easily replaceable filter, or an expensive lens.
    Yes, I know that good quality filters are expensive, but they would be less
    expensive than the lens itself.

    You pays your money and you takes your choices.
     
    Ken Hart1, Sep 10, 2008
    #3
  4. Walter Banks

    mj Guest

    For better than 20 years I serviced both 35mm and most medium format
    systems. I can say that in a small percentage of all the lenses I have
    repaired (less then 20%) I have seen "protection" filters break into the
    front element of the lens scratching it. Hoods generally offer better impact
    protection. IMO
     
    mj, Sep 10, 2008
    #4
  5. Walter Banks

    Bruce Guest


    How much protection does a hood offer against damaging the front
    element of the lens through careless cleaning?

    A filter is extremely easy to clean. You can even take it off the
    lens to clean it. If you scratch or damage a filter, it is quick and
    relatively cheap to replace. Try doing that with the front element of
    a good quality lens, and you will be faced with a very large bill.

    [Of course you could always sell it on eBay, claiming that the
    defective front element did not affect the quality of the images
    produced ... funny how many lenses on eBay are thus described!]

    With film, the often alleged optical degradation through using a
    filter was a non-issue as long as good quality multi-coated filters
    were used. However, things have changed a little with digital because
    of the greater reflectivity of the digital sensor. Whether the latest
    filter coatings have made this a non-issue once again is a moot point.
     
    Bruce, Sep 10, 2008
    #5
  6. Walter Banks

    Dave Guest

    mj wrote:
    You pays your money and you takes your choices.

    You need very careful to understand the implications of that statistic.

    As a lens repair person you say you see 20% of lenses where the filter
    has damaged the lens. I don't dispute that at all. But it does *not*
    mean that 20% of the lenses which have UV filters suffer such damage.
    Most people, who damage their filters will do it in a far less
    catastropic manner. They are likely to put a scratch on the filter,
    replace the filter and not send the lens for repair.

    Also, whilst I accept filters can damage the lens if hit sufficiently
    hard, one would have to question whether the lens would have been
    damaged anyway without the filter. If a knock is sufficient to damage a
    filter and smash it into a lens, it must have taken quite a knock -
    quite possibly enough to have damaged the lens anyway.

    I personally tend to use filters all the time. I might make an exception
    on my Nikon macro lens though. The front element is very well recessed,
    making damage to the element unlikely. Whilst I have never proved this,
    I suspect a filter is more likely to degrade an image if the object is
    focused very close, which is what one is likely to do on a macro lens.

    But since the element on the micro nikkor lens is very well recessed, it
    will be difficult to clean, so perhaps there is a good reason to buy a
    UV filter.

    Scratches on lens elements have a very significant effect on resale
    value. There is for example a Nikon 600 mm lens for sale:

    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220278589593

    This would be perfect for me.

    * Just the lens I am looking for.
    * Seller is only 40 miles away.
    * Seller happy for me to pick it up.
    * I can avoid the very significant risks of Paypal on items over $2000.

    But that 600mm lens has a small scratch on the front element, and is a
    bit tatty in places. Whilst I did bid, I am not going to bid again. It
    has reached $4900 which I feel is enough for a lens with a scratch on
    it. Had the condition been better, I would certainly have bid a lot
    more, especially as it is very local to me.



    I would rather see an auction where the seller says "has had a UV filter
    on from day one" than "has a small scratch but does not degrade image".
    Clearly scratches are more likely to cause problems when shooting into
    the light.
     
    Dave, Sep 10, 2008
    #6
  7. Walter Banks

    jimkramer Guest

    When to use a filter...
    http://www.fredmiranda.com/forum/topic/685667
    Not mine, but a nice picture none the less.
    -Jim
     
    jimkramer, Sep 10, 2008
    #7
  8. Walter Banks

    mj Guest

    Which is why I said less then 20% of the lenses I have *repaired*.
    The result of impact damage is a crap shoot at best. I have seen lenses that
    fell a foot or two and were wiped out then there are the ones that drop
    three feet and only bend the filter ring.
    While most of my 35MM customers used "protective filters" not one of my MF
    customers did and not all of my MF customers were "professionals".
     
    mj, Sep 10, 2008
    #8
  9. Walter Banks

    Robert Coe Guest

    :
    : : >I would like to see the pro's and cons of a UV filter or some other "lens
    : >protecting" glass on a lens.
    : >
    : > The small ghosts on very high contrast shots suggests that this is not a
    : > good idea. It has to degenerate even normal images.
    : >
    : > w..
    : >
    :
    : Every piece of glass in the light path has some effect on the image.
    :
    : On the other hand, if something scratches the front of the lens, would you
    : prefer that scratch on an easily replaceable filter, or an expensive lens.
    : Yes, I know that good quality filters are expensive, but they would be less
    : expensive than the lens itself.

    Laying aside the lens protection issue for a moment ...

    In the film days we used UV filters to cut through haze. It worked (more or
    less) because film was sensitive to UV light, which was scattered by water
    droplets in the air and tended to obscure the image. But what about a digital
    sensor? Is it sensitive to UV light at all? (It sees only red, green, and
    blue, right?) And if it isn't, is there any reason to use a UV filter other
    than for lens protection?

    Bob
     
    Robert Coe, Sep 14, 2008
    #9
  10. Walter Banks

    Robert Coe Guest

    : FWIW, I just replaced a UV filter (Hunt's, Melrose, MA.), which is used
    : primarily for "protection." Never did figure out how the filter
    : shattered sitting in the camera bag...

    I assume you've ruled out catastrophic physical contact, such as getting
    banged by a lens, camera, or flash unit. That leaves stress fracture, one
    contributor to which could be excessive heat. Did you leave the bag in a hot
    car, for example? The diameter of a metal ring increases when the ring is
    heated. If a filter's ring is too tightly glued to the glass, heating it will
    put the glass in tension, possibly causing it to shatter. The effect might be
    exacerbated if the filter is on a lens but screwed on crookedly, since that
    might have already caused stresses in the glass.

    The Hunt's store in Harvard Square is disappointingly tiny. Is the one in
    Melrose larger? Unfortunately, it's a bit off the beaten path for me. Is it
    within walking distance of a commuter rail station? Or if one drives, is there
    any place to park?

    Bob
     
    Robert Coe, Sep 14, 2008
    #10
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