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Thread: Lens hoods advice

  1. #11

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    Re: Lens hoods advice

    Quote Originally Posted by Once View Post
    Oh, oh - slow down, please. Where do you have that from? Surely not from an experience. Do you realise it is not correct, neither for the length nor for the difference made?
    Do you have first hand experience that it is not correct? If so, I'm curious about your testing methodology. I too was skeptical of the importance of a hood until I saw this test by Robert Zeichner (a forum member) titled "Can better shades improve lens performance?".

    http://web.mac.com/razeichner/RAZP_l...hade_pg_1.html

  2. #12
    Joanna Carter's Avatar
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    Re: Lens hoods advice

    Quote Originally Posted by Tony Karnezis View Post
    Do you have first hand experience that it is not correct? If so, I'm curious about your testing methodology. I too was skeptical of the importance of a hood until I saw this test by Robert Zeichner (a forum member) titled "Can better shades improve lens performance?".

    http://web.mac.com/razeichner/RAZP_l...hade_pg_1.html
    I saw that article some time ago and found it interesting and the results are certainly demonstrably better than no hood. In theory such a short hood doesn't quite give the protection that a longer one would; but, then, have you ever tried fitting a 210mm deep hood on the front of anything other than a monorail camera? Which is why I settled for the compromise of the Lee hoods for use on my Ebony
    Joanna Carter
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  3. #13

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    Re: Lens hoods advice

    Quote Originally Posted by Joanna Carter View Post
    Yes, from personal experience. Even with a Lee Hood, which is only really long enough for a 90mm lens, the difference in contrast is noticeable even on a 210mm lens.

    I also attended a masterclass, where the the photographer giving it showed a Sinar setup for studio work, with a second set of bellows used as a "full length" hood for a 210mm lens and the difference in contrast was even visible on the GG screen.

    It's all matter of eliminating any extraneous light from outside of the image area. If you've never tried using a proper deep hood, like me, you may not realise just how much difference it can make.
    So let’s put the things in some light. First of all, somehow (a strange type error?) you contradict yourself, saying first that anything less than the focal length might not cut out enough light to make enough difference and then going to say that the difference in contrast is noticeable even on a 210mm lens and 90mm length of a lens shade.

    Secondly - (to go back to your first incorrect saying) - you don’t need and don’t have lens shades long 600mm or even 1200 mm for lenses of those focal lengths. Not only would it be impractical ad absurdum but unnecessary too. Why? Because the length of the shade has a very small impact after a certain «*optimal*» length. Say, to name an example, you have the Fujinon C 600 lens. If you make a lens shade of 600mm length you eliminate (under certain given conditions, without going into details) 95% of the stray light vertically on 4x5 film format. If you make the lens shade long 400mm you get the percentage down to 92%. If you make the lens shade long 200mm you get the percentage down to 83%. You see that the huge difference in the length of the shade makes just a small effect on the percentage of the offending light getting on the film. But - even 60 % (or 50% ) of the eliminated stray light makes a very important difference (clearly visible) on the picture. Usually, the «*optimal*» length after which making the shade longer is not practically important and viable is about 70%. After that, you add an unwieldy length to the shade with a small improvement in the optical performance.
    So much for an example.

    By now you probably understood that me too I know about lens shade construction something... Regards, GPS

  4. #14

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    Re: Lens hoods advice

    Quote Originally Posted by GPS View Post
    So let’s put the things in some light. First of all, somehow (a strange type error?) you contradict yourself, saying first that anything less than the focal length might not cut out enough light to make enough difference and then going to say that the difference in contrast is noticeable even on a 210mm lens and 90mm length of a lens shade.

    Secondly - (to go back to your first incorrect saying) - you don’t need and don’t have lens shades long 600mm or even 1200 mm for lenses of those focal lengths. Not only would it be impractical ad absurdum but unnecessary too. Why? Because the length of the shade has a very small impact after a certain «*optimal*» length. Say, to name an example, you have the Fujinon C 600 lens. If you make a lens shade of 600mm length you eliminate (under certain given conditions, without going into details) 95% of the stray light vertically on 4x5 film format. If you make the lens shade long 400mm you get the percentage down to 92%. If you make the lens shade long 200mm you get the percentage down to 83%. You see that the huge difference in the length of the shade makes just a small effect on the percentage of the offending light getting on the film. But - even 60 % (or 50% ) of the eliminated stray light makes a very important difference (clearly visible) on the picture. Usually, the «*optimal*» length after which making the shade longer is not practically important and viable is about 70%. After that, you add an unwieldy length to the shade with a small improvement in the optical performance.
    So much for an example.

    By now you probably understood that me too I know about lens shade construction something... Regards, GPS
    That is why some manufacturers include or offer cropping masks for the front of the shade so you don't need to have a bellows equal in length to the camera bellows.

  5. #15

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    Re: Lens hoods advice

    Really? Hmm. Bob, I'm the one standing behind the origin of the Lee lens shades...

  6. #16

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    Re: Lens hoods advice

    Quote Originally Posted by GPS View Post
    Really? Hmm. Bob, I'm the one standing behind the origin of the Lee lens shades...
    I am not talking about the Lee shade. I am listing a feature of a true compendium for a view camera.

  7. #17

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    Re: Lens hoods advice

    Hmm. Could it be why you miss the point?

  8. #18

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    Re: Lens hoods advice

    Quote Originally Posted by Bob Salomon - HP Marketing View Post
    That is why some manufacturers include or offer cropping masks for the front of the shade so you don't need to have a bellows equal in length to the camera bellows.
    So, theoretically, you could just insert cropping masks right at the lens rim and voilà - you don't need any longer lens shade? Geometry, geometry...

  9. #19

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    Re: Lens hoods advice

    Another question, Bob. When a mask of the film format size put at the focal distance of the lens eliminates (as you affirm elsewhere) all the extraneous light why is it that a half size mask does not do the same at a half of the focal length?

  10. #20

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    Re: Lens hoods advice

    Or the other way round - why - when a half size film format mask put at a half focal length distance does not eliminate all the extraneous light - the mask in the film format size put at the full focal length distance suddenly does (according to you) eliminate all the stray light? What doesn’t give?
    Geometry, geometry...

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