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Thread: Does changing aperture move the focus point

  1. #1

    Does changing aperture move the focus point

    Hello,

    If I focus the camera at a brighter aperture so that I can see the object on the ground glass, and then change the aperture does that move the focus point or just change the depth of field?

    I have never made an exposure and about to make my first attempt.

    I have purchased a fresnel screen yesterday does anyone have tips for focusing when it's dark?

  2. #2

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    Re: Does changing aperture move the focus point

    It can, varies from lens to lens. Check you focus after stoping down.

  3. #3

    Re: Does changing aperture move the focus point

    The lens is a Goerz 12" dagor it's barrel mounted and I have the sinar copal shutter.

    It's too dark to see. As I close the aperture it seems to get sharper. I'm focusing on some wood grain and it gets sharper and then it gets too dark to see.

    8 x 10 film is so expensive i'm loath to pull the trigger so to speak.

    Think i'll wait for the fresnel and see if that helps.

  4. #4
    Peter De Smidt's Avatar
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    Re: Does changing aperture move the focus point

    Ok. Well, use some ingenuity. Place a flashlight at a normal subject distance pointed at the camera. Focus (with a good loupe) wide open. Stop down. Check focus. A Fresnel will not help with this at all.
    May tomorrow be a better day.

  5. #5

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    Re: Does changing aperture move the focus point

    Focus shift from full aperture to stopped down as exampled by stopping down to f16 or smaller, modern view camera lenses exhibit about zero focus shift. They were designed to be focused full aperture then stopped down to taking aperture, as viewed on the GG.

    Vintage lenses like Dagor, focus shift depends on the specific example of Dagor. Some have focus shift, others very little focus shift from full aperture.

    Keep in mind what is focused on IS what will be a true focus or the actual focus plane. This can be adjusted and bent by applying camera movements. Stopping down the lens results in more of the image going into apparent focus or the appearance of "sharper" but not in true focus as what is at the set plane of focus.

    Learning how to see and view the stopped down image on the GG is an essential part of learning how to view camera. While a fresnel might help, it can be a problem depending on lenses used and image making conditions. Fresnel viewing aids are not a panacea cure-all view camera GG visual realities. If the fresnel is not properly installed, it will not properly register the view camera image to the film in film holder causing blurry image where the focus area was set. While a fresnel can produce a brighter GG image on axis of the GG and fresnel combo, fresnel lenses have grooves (how they work) which can hinder the view camera GG image when a magnifier is used to assess actual focus.

    There are other factors from alignment-registration from GG to film in film holder distance which must be within a specific tolerance. Camera alignment/precision of lens to film holder area and more.

    If you're un-willing to "pull the trigger" due to cost of 8x10 film, why do 8x10 film? Burning film is an essential part of learning how to view camera.


    Bernice




    Quote Originally Posted by tenniss_balls View Post
    The lens is a Goerz 12" dagor it's barrel mounted and I have the sinar copal shutter.

    It's too dark to see. As I close the aperture it seems to get sharper. I'm focusing on some wood grain and it gets sharper and then it gets too dark to see.

    8 x 10 film is so expensive i'm loath to pull the trigger so to speak.

    Think i'll wait for the fresnel and see if that helps.

  6. #6

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    Re: Does changing aperture move the focus point

    GOOD suggestions here, based on real world view camera experience.


    Bernice


    Quote Originally Posted by Peter De Smidt View Post
    Ok. Well, use some ingenuity. Place a flashlight at a normal subject distance pointed at the camera. Focus (with a good loupe) wide open. Stop down. Check focus. A Fresnel will not help with this at all.

  7. #7

    Re: Does changing aperture move the focus point

    OK thanks for the replies. It was difficult to see the wood grain because the angle of the light was not reflecting back to the lens where I wanted to focus. I moved the light and checked wide open and stopped down. It doesn't look much different. Sharper and more contrasty.

    Thanks for the flashlight suggestion.

    I have to say working and thinking about every aspect of your imagery is very theraputic! And i'm amazed by the image on the ground glass. I'ts surprising what details you can see through the loupe.

    The loupe I have is a Silvestri. Not too sure of it's quality.

    Is there a particularly good quality loupe which is recommended?

  8. #8
    Alan Klein's Avatar
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    Re: Does changing aperture move the focus point

    Quote Originally Posted by gypsydog View Post
    It can, varies from lens to lens. Check you focus after stoping down.
    I have Nikkor Schneider and Fujinon. Do these or not?

    In any case, why would LF lenses change focus points and DSLRs don't? Every shot one takes with a DSLR stops down when you press the shutter. I've never heard of this problem. I've got enough problems learning LF. Let's not create more problems for me.

  9. #9

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    Re: Does changing aperture move the focus point

    Quote Originally Posted by Alan Klein View Post
    I have Nikkor Schneider and Fujinon. Do these or not?

    In any case, why would LF lenses change focus points and DSLRs don't? Every shot one takes with a DSLR stops down when you press the shutter. I've never heard of this problem. I've got enough problems learning LF. Let's not create more problems for me.
    Guess you never used an Imagon. It changes focus with each disk setting used. So you have to focus at your choice of setting, not widen open.

  10. #10
    Mark Sawyer's Avatar
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    Re: Does changing aperture move the focus point

    Berenice was quite right in post #5.

    I'll add that focus shift is the result of spherical aberration, which is also the driving force behind the soft focus effect. The outer area of the lens is focusing on a slightly different plane than the center. As you shut down the aperture, outer areas of the lens are blocked, and the dominant focus shifts to the center of the lens.

    Early Dagors still had a bit of spherical aberration, hence the famous "Dagor Glow". By the time Dagors were coated, the spherical aberration had been corrected and the glow and focus shift were gone.

    If your lens doesn't have spherical aberration, it won't have focus shift. And any sharp modern lens will be well-corrected for spherical aberration.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

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