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Thread: UWA lens hood

  1. #1
    Alis's Avatar
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    UWA lens hood

    Does anyone know why an UWA lens like a Canon 16-35mm f/2.8 would need a hood. Obviously it is not doing what a hood is supposed to do optically.

    My guess is that it acts sort of like a shock absorber. Is this correct?

    Or is it just there as an ornament for consistency among all the Canon L lens seris?

    Thanks,

    Alis

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    Moderator Dave Humphries's Avatar
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    Re: UWA lens hood

    OMG that's heresey!

    Or is it just there as an ornament for consistency among all the Canon L lens seris?
    Don't let Colin hear you say that!

    What makes you think it won't work like a nomal hood?
    OK (I haven't seen a pic of it), but I'm guessing it's quite thin.

    But the bulbous front elements on a UWA need all the protection they can get from stray light to keep flare under control.

    My guess is that it acts sort of like a shock absorber.
    Or is it one of the rubbery ones?

    Regards,

  3. #3
    Alis's Avatar
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    Re: UWA lens hood

    Quote Originally Posted by Dave Humphries View Post
    OMG that's heresey!


    Don't let Colin hear you say that!
    Slow down! I probably use the hood on my lenses more than anybody else on this forum.

    Did not mean any disrespect to Colin or Canon.

    What makes you think it won't work like a nomal hood?
    Just looking at this thing (and a little help from Newton and Einstein) , I am not sure if it works that well to prevent flare, of course assuming that light follows a straight line. I can see everything insde it from every angle I want.

    I think all it does is to prevent me from putting it upright on the shelf, hood down like all other lenses I have.

    OK (I haven't seen a pic of it), but I'm guessing it's quite thin.
    Here is a picture:

    UWA lens hood


    But the bulbous front elements on a UWA need all the protection they can get from stray light to keep flare under control.


    Or is it one of the rubbery ones?
    No it is solid plastic!
    Last edited by Alis; 9th August 2009 at 02:37 AM.

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    Moderator Dave Humphries's Avatar
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    Re: UWA lens hood

    Hi Alis,

    It is very thin (probably even more than I imagined), but from the angle of the photos, I can't see the front element, so if I were the sun, I wouldn't be causing flare!

    I'm impressed you can afford 3 though

    Cheers,

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    Re: UWA lens hood

    Hi Ali,

    Interesting topic!

    I'm sure that it's effective over the range of angles that it's designed for, but obviously (as you point out) being an UWA lens, it's not possible to block light (wanted or unwanted) that originates from within the lenses field of view. Perhaps it's a bit like those who want a really tiny laptop computer (for ease) of transport, but with a large keyboard and screen for ease of use.

    Interestingly, the EF24-70mm F2.8L USM has a unique design with regards to lens hoods in that the front element moves forward as the lens zooms to a wider angle, thus the hood can be made deeper than would otherwise be possible.

    I probably use the hood on my lenses more than anybody else on this forum.
    I always use a hood on mine when I'm in "walk about" mode ... but, lets see if you can figure this one out ...

    ... I sometimes put it on backwards when shooting sunsets (5 brownie points to anyone who can figure out why)

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    William W's Avatar
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    Re: UWA lens hood

    The "problem" with the "efficiency" of a lens hood for a zoom lens is it has to be designed not to optically vignette at the widest zoom FL. . . so the 16 to 35's hood is designed for the 16mm - not the 35mm. This "problem" is exacerbated for the ultra wide zooms. (like it is NOT a problem for the 70 to 200, as an example).

    If one happens to be very clinical about the lens choices for a kit, as well as there being an economic advantage for buying Zooms and Primes with the same filter size (economic advantage for a CPF for example . . .), there is also a strategic advantage for lens hood cross-use.

    An example of this is the EF24F/1.4L and the 16 to 35F/2.8L - the 24's hood is effective on the 16 to 35, for the outer range of the zoom - MORE effective than the original zoom hood.

    ***

    Quote Originally Posted by Colin Southern View Post
    ... I sometimes put it on backwards when shooting sunsets (5 brownie points to anyone who can figure out why)
    Hmm . . . I love puzzles, but I am at a loss . . though, I will guess it might allow any ghost image to be seen more clearly??? but I really dunno . . .

    I can state why I use the hood on backwards . . . it so I don't loose the bloody thing!

    Oh yes - when would I do that? . . . macro sometimes, and when shooting against glass or a fence . . . are two examples - - - but I can indeed pull out a "Sunset" with my len hood on backwards, Colin . . .

    It used to be high-rise Hotels had Balconies – now they have Triple Plated Glass on Windows which cannot be opened – what a pain in the butt that is . . .

    Shot “AGAINST GLASS” with the hood on backwards and a dark coat wrapped over the lens to form a light seal. Hand-held - I didn’t do that “IS” stuff . . . there would be no challenge to it !

    WW

    "Landmark Architecture at Sunset"
    Tech Specs: Canon 5D + 70 to 200F/2.8L @ 190mm F/3.2 @ 1/400s ISO800 HH.


    UWA lens hood
    Last edited by William W; 9th August 2009 at 04:01 AM. Reason: to correct my spelling

  7. #7
    Alis's Avatar
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    Re: UWA lens hood

    Quote Originally Posted by Colin Southern View Post
    Hi Ali,

    Interesting topic!

    I'm sure that it's effective over the range of angles that it's designed for ...
    How can it be effective when the rim is not uniform. Obviously, some parts of it should be ineffective, depending on how you mount it on the lens and where the light is coming from, at least two side of it should allow flare.

    ... but, lets see if you can figure this one out ...

    ... I sometimes put it on backwards when shooting sunsets (5 brownie points to anyone who can figure out why)
    Because you actually want flare in your picture?

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    Re: UWA lens hood

    Quote Originally Posted by Alis View Post
    How can it be effective when the rim is not uniform. Obviously, some parts of it should be ineffective, depending on how you mount it on the lens and where the light is coming from, at least two side of it should allow flare.
    Alis think angles, both vertical and horizontal, and of course the corners. The alternative to the existing hood can be summed up in one word......VIGNETTE.

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    William W's Avatar
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    Re: UWA lens hood

    Quote Originally Posted by Alis View Post
    How can it be effective when the rim is not uniform. Obviously, some parts of it should be ineffective, depending on how you mount it on the lens and where the light is coming from, at least two side of it should allow flare.
    In theory, because of the way the bayonets on the lens hood mate with the slots on the lens, it can only be mounted the "correct way", to do as Bill 44 described above - address the different FoV.

    The "petals" (which is the technical name for the curved bits which stick out) are designed around the FoV (Field of View) of the lens as that changes from the Perfectly Horizontal FoV, through the Diagonal FoV (which is the cut away area of the hood) to the perfectly Vertical FoV.

    But, obviously the Vertical FoV is different to the Horizontal FoV - so too are the Petals a diiferent size.

    WW

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    Re: UWA lens hood

    Quote Originally Posted by Colin Southern View Post
    ... I sometimes put it on backwards when shooting sunsets (5 brownie points to anyone who can figure out why)
    I am going to have another crack at this:

    I reckon you are out to get a cracker sunset and you have your 16 to 35 and Camera mounted on that 85Kg tripod you crane around with you and you have your remote release attached, and you know you only have about 3 to 5 minutes to pull about eight to ten frames and the light is changing rapidly and you have a CPF on the front and you have (like me) . . . fat fingers

    Even if I am wrong - it is a great story!

    WW

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    Re: UWA lens hood

    I would say that Colin has the hood on backwards so that:-

    1. He has access to the variety of filters he uses.

    2. So he doesn't lose it, it's pretty hard to access your pockets when you have waders on.

  12. #12
    Moderator Dave Humphries's Avatar
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    Re: UWA lens hood

    Both Bill's ideas are good and 1. is almost there (I think);

    The filter holder for the GND, which needs to be slid up or down, won't attach in front of the lens hood.
    Rectangular filter, but round mount lens hood!

    Thereafter, Bill's No.2 comes into play!
    And anyway, if I were to put one of those hoods in my pocket it would go in whole and come out as a kit

    Plus (for a bonus brownie point) he's often shooting into the light, so any veiling flare from the sky is going to be insignificant compared to what's in his field of view.

    Am I close?
    .. and if I am, I think Bill gets the points, not me, as I only extrapolated his idea (but then William said CPF, which I know Colin rarely uses, but got us on the filter idea).

    Cheers,
    Last edited by Dave Humphries; 9th August 2009 at 07:46 AM. Reason: last bit added

  13. #13

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    Re: UWA lens hood

    I will guess it might allow any ghost image to be seen more clearly???
    Nope

    Because you actually want flare in your picture?
    Nope

    I reckon you are out to get a cracker sunset and you have your 16 to 35 and Camera mounted on that 85Kg tripod you crane around with you and you have your remote release attached, and you know you only have about 3 to 5 minutes to pull about eight to ten frames and the light is changing rapidly and you have a CPF on the front and you have (like me) . . . fat fingers
    Nope

    1. He has access to the variety of filters he uses.

    2. So he doesn't lose it, it's pretty hard to access your pockets when you have waders on
    Nope

    Am I close?
    Nope

    I'll give you all a clue - think "Focus"

  14. #14
    Moderator Dave Humphries's Avatar
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    Re: UWA lens hood

    So you don't knock it off (focus)?

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    Re: UWA lens hood

    Quote Originally Posted by Dave Humphries View Post
    So you don't knock it off (focus)?
    Pretty much - but lets see if you can decode more of the story

  16. #16
    Moderator Dave Humphries's Avatar
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    Re: UWA lens hood

    No time now, out with camera shortly, I'll leave that to someone else unless I get inspired

    To White Waltham Airfield (look it up) - and no, there won't be any F/A-18s there!

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    Re: UWA lens hood

    Another try, Colin are you measuring your hyperfocal distance from the front of the lens? I thought it was measured from the focal plane?

    Would you happen to have a handy gadget that rests against the front of the lens and has a focus point at the required distance?

  18. #18

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    Re: UWA lens hood

    Quote Originally Posted by Bill44 View Post
    Another try, Colin are you measuring your hyperfocal distance from the front of the lens?
    Nope

    I think I'd better put you all out of your misery ...

    Actually, it's not that sa-fish-tee-kated - when shooting low light stuff I'm often there and setup while light levels are still high enough for reliable AF ... but later on it often too dark to rely on AF or to focus manually. So easiest thing is just to use the AF initially - double-check it - and then switch to manual and then "just don't touch it" - and I've found that if I put the hood on backwards it covers the focus ring so if my hand goes into that area then it bumps into the hood first (often I have to make adjustments by feel).

  19. #19

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    Re: UWA lens hood

    Quote Originally Posted by Colin Southern View Post
    Nope

    I think I'd better put you all out of your misery ...

    Actually, it's not that sa-fish-tee-kated - when shooting low light stuff I'm often there and setup while light levels are still high enough for reliable AF ... but later on it often too dark to rely on AF or to focus manually. So easiest thing is just to use the AF initially - double-check it - and then switch to manual and then "just don't touch it" - and I've found that if I put the hood on backwards it covers the focus ring so if my hand goes into that area then it bumps into the hood first (often I have to make adjustments by feel).
    Damn, I wrote that off for the very reason that you couldn't get to the focus ring.

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