Fresnel lens and ground glass question

Discussion in 'Large Format' started by terry_evans|3, Dec 1, 2008.

  1. Hello,

    I just bought a Sinar F as my first lf camera. I want to increase the ability to see and focus through the ground
    glass. I have read about fresnel lenses, and assume they are a separate lens that mounts behind the original ground
    glass. On eEbay, there is a Sinar Fresenel lens + Ground glass, new from Sinar. Is this the two combined and I
    just replace my original ground glass?

    Thanks for your help,

    Terry
     
  2. Hi Terry. Yes, you use a fresnel in conjunction with the ground glass, and the fresnel is placed behind the GG (lens side). Fresnels have one side which is smoother than the other, and my Ebony wide angle fresnel faces in the opposite direction to most. I can't be sure without checking, which way round it is though, but i'm sure a Sinar user will fill you in on the rest. Stu
     
  3. A Fresnel lens can be placed on either side of the ground glass, but if it is placed on the lens side of the ground glass it changes the focus. If you take a camera in which focusing on the ground glass causes the focus to be correct on the film and just insert a Fresnel lens in front of the ground glass, you will introduce a focus error. Cameras can be designed for the configuration of Fresnel in front of the ground glass, which has the advantage that the plastic Fresnel lens is protected. But if you want a removable Fresnel lens, or to retro-fit a Fresnel lens to a camera that doesn't have one, it is much easier to install it on the photographer's side of the ground glass. On this side there is no change to the focus.
     
  4. If it is the original Sinar fresnel it it mounted in a black plastic frame with a tab handle. They snap into the groundglass frame behind the GG.
     
  5. Thank you all. Now I just need to find a fresnel lens mounted in a holder. I can buy them all day without one. Again, thanks.
     

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