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Thread: Focusing Puzzler

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    Focusing Puzzler

    I'm having difficulty figuring out a focusing problem and would appreciate any suggestions.

    I use a Hassy Flexbody with a P45+. When I use an 80mm or larger lens the image circle is large enough to allow me to use the full rise/fall range of the Flex. So putting the P45 on with sensor horizontal allows me to do one exposure with the rear standard at full rise and one at full fall position and stitch. So far, so good

    Now here's where I get messed up. If I want to use tilt to get near/far for the entire stitched image, I think I have to focus and tilt when the back is in full rise position and then refocus and re-tilt when it's in the full fall position. Or, do I only need to use tilt when I'm in the full rise position (on the nearer objects) and no tilt focusing, but do refocus for distance, when in the full fall position (on the far objects).

    Thanks for any advice offered for using a technique for this body.
    Bob

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    Re: Focusing Puzzler

    The camera is designed to work with a 56mmX56mm "sensor" so as long as you're within that image area (~10mm rise/ fall), I believe that you don't need to change the front tilt and focusing.

    To be safe I'd do the tilt/ focus with the sensor in the centre position, this way you will have smaller difference between the top & bottom frames, if any.

    Yair
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    Re: Focusing Puzzler

    I have a Flexbody, but I have not used it with a digital back... I have just downloaded the manual from the Hasellblad web site.

    Quote Originally Posted by rga View Post
    I'm having difficulty figuring out a focusing problem and would appreciate any suggestions.

    I use a Hassy Flexbody with a P45+. When I use an 80mm or larger lens the image circle is large enough to allow me to use the full rise/fall range of the Flex. So putting the P45 on with sensor horizontal allows me to do one exposure with the rear standard at full rise and one at full fall position and stitch. So far, so good
    With the full 56mm * 56MM sensor you can use about the full 15mm of shift with the 100, 120 and 150 lenses, an 10 MM with the 60 & 80.

    I have the 40mm, which has no spare image circle for shift on the 56 square, but could be used with shift on smaller sensors.

    Now here's where I get messed up. If I want to use tilt to get near/far for the entire stitched image, I think I have to focus and tilt when the back is in full rise position and then refocus and re-tilt when it's in the full fall position. Or, do I only need to use tilt when I'm in the full rise position (on the nearer objects) and no tilt focusing, but do refocus for distance, when in the full fall position (on the far objects).

    Thanks for any advice offered for using a technique for this body.
    Bob
    Changing the tilt setting between stitched shots might work, but it might make it difficult for the stitching software... generally leave the tilt the same for both shots.

    Focusing would be more critical for the foreground subjects, so set tilt and focus @ full rise... check background focus and re-adjust tilt if needed.

    You can re-focus for the second shot if you need to. a decent tech camera (like the Flexbody with its own tripod mounting socket) lets you adjust the shift without affecting focus.

    It seem that whoever wrote the Manual did not understand how to use a tech camera!

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    Re: Focusing Puzzler

    Hi Yair,
    There is no front movement on the camera. The problem I am seeing when I don't change the tilt and shift the rear standard down, I now have backward tilt of the top of the rear standard. This was ok for focusing the foreground when the rear standard was at the top. But now that the top of the rear standard is ~1/3 into the image, the focus is not correct. This, I think, is what causes problems and why I think I need to refocus...
    Bob

    Quote Originally Posted by yaya View Post
    The camera is designed to work with a 56mmX56mm "sensor" so as long as you're within that image area (~10mm rise/ fall), I believe that you don't need to change the front tilt and focusing.

    To be safe I'd do the tilt/ focus with the sensor in the centre position, this way you will have smaller difference between the top & bottom frames, if any.

    Yair

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    Re: Focusing Puzzler

    Quote Originally Posted by dick View Post
    I have a Flexbody, but I have not used it with a digital back... I have just downloaded the manual from the Hasellblad web site.
    Nice it's still online, yes? (even though it's somewhat useless)...

    With the full 56mm * 56MM sensor you can use about the full 15mm of shift with the 100, 120 and 150 lenses, an 10 MM with the 60 & 80.
    Yes.

    I have the 40mm, which has no spare image circle for shift on the 56 square, but could be used with shift on smaller sensors.
    Agreed. 50 doesn't give a lot either.

    Changing the tilt setting between stitched shots might work, but it might make it difficult for the stitching software... generally leave the tilt the same for both shots.
    But if you do that then the backward tilt of the top of the rear standard that you used to get the near objects in focus is now being applied about 1/3 further toward the top of your image area. This makes that area OOF.

    Focusing would be more critical for the foreground subjects, so set tilt and focus @ full rise... check background focus and re-adjust tilt if needed.
    Agreed except for above...

    You can re-focus for the second shot if you need to. a decent tech camera (like the Flexbody with its own tripod mounting socket) lets you adjust the shift without affecting focus.
    Unless you have tilt which now effects a different part of the image. So if you refocus would that give a differently framed image that would cause stitching problems?

    It seem that whoever wrote the Manual did not understand how to use a tech camera!
    They did OK on the shift stuff, but not on the tilt/Scheimpflug part. You also need that special cable that wakes up the Phase back after you close the lens (first gentle push of the cable release). Then you have 5 seconds to make exposure... Special cable not needed with the Leaf backs.

    Thanks for the thoughts!
    Bob

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