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Thread: Fresnel for LF? Need some clarity, please!

  1. #1

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    Question Fresnel for LF? Need some clarity, please!

    I've been thinking I want to add a fresnel lens to my focus screen for my 4x5 camera but after reading around the web, I keep seeing conflicting info about this.

    My desire is to brighten the screen, the camera and my lens focus fine it is just a little dark. And I don't want to spend a ton of $ for this--it's about convenience not necessity.

    Initially, I figured to just find some inexpensive fresnel and put it on the back/out side of the screen, the side facing away from the lens. This, I think, wouldn't change where the image is formed for focus and would, I thought, just increase apparent brightness.

    However , after spending this morning reading about this, I am seeing lots of disagreement about the correct way to do this.

    I'm a little interested in the theory about this but am much more interested in empirical/practical application.

    So, who's got the straight poop on this?

    Thanks!
    Rob
    _____

  2. #2

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    Re: Fresnel for LF? Need some clarity, please!

    The straight poop is that it depends on the camera. Some have backs were made to accept a fresnel in front of the GG and have lost the fresnel. This sometimes happens with, for example, some, not all, post-1949 Pacemaker Graphics. Most backs are made without any thought of a fresnel; with them, it should go behind the GG.

    The first step to a brighter GG is washing it, making sure to put it back in the focusing panel ground side facing the lens.

  3. #3

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    Re: Fresnel for LF? Need some clarity, please!

    Quote Originally Posted by Dan Fromm View Post
    The straight poop is that it depends on the camera. Some have backs were made to accept a fresnel in front of the GG and have lost the fresnel. This sometimes happens with, for example, some, not all, post-1949 Pacemaker Graphics. Most backs are made without any thought of a fresnel; with them, it should go behind the GG.

    The first step to a brighter GG is washing it, making sure to put it back in the focusing panel ground side facing the lens.
    Dan,
    Thank you for that good info!

    I should have been more clear in my initial post: the camera is my 6 month old Intrepid. So, effectively new and not made to have a fresnel, just the ground glass.

    Thanks!
    Rob

  4. #4

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    Re: Fresnel for LF? Need some clarity, please!

    I've never dealt with the Intrepid folks, but by all accounts they're quite decent. Why don't you ask them what you should do?

  5. #5

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    Re: Fresnel for LF? Need some clarity, please!

    If your camera already works fine without the fresnel, put the fresnel on your side of the ground glass, not the lens side.

  6. #6

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    Re: Fresnel for LF? Need some clarity, please!


  7. #7

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    Re: Fresnel for LF? Need some clarity, please!

    Alan's method in the video is to apply the Fresnel to the inside of the holder (i.e. in front of the GG - Fresnel facing lens) it takes him a bit of dremel work to get the Intrepid to take it.

    For an alternate look at Justin Lowery's Intrepid review, where he affixes a Fresnel to the outside (above the GG - photographer side). You can also see a video from Nicos Photography Show that shows him installing a Fresnel for his Chamonix 4x5 while different than an Intrepid it's mounted on the outside (just for reference).

    I'm thinking of adding one myself but on-stop of the GG, Justin's method (i.e. on the outside with GG facing lens).

  8. #8

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    Re: Fresnel for LF? Need some clarity, please!

    I would buy a cheap reading fresnel first, and mount it on top of the ground glass to see if you like the result. The purpose of a fresnel isn't to brighten the view as much as to turn the light from the edges inwards towards your eye so that the whole view is more evenly illuminated. A quick check with a $5 reader will tell you if that's something you think is an improvement. If not, then you need to search for a brighter, aftermarket ground glass ($$$). Others will have more to say about that--I've always been happy with whatever came with my cameras.
    Thanks, but I'd rather just watch:
    Large format: http://flickr.com/michaeldarnton
    Mostly 35mm: http://flickr.com/mdarnton
    You want digital, color, etc?: http://www.flickr.com/photos/stradofear

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