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    Alan Klein's Avatar
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    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Doremus Scudder View Post
    Well, here's what I would do (a bit different approach than Vaughn and Kiwi).

    Since it's a building, I'd want the verticals parallel, so I'd set up the camera with the back level and check the verticals against the grid on my ground glass, adjusting the tripod tilt to get them right.

    Then I'd use a little bit of front tilt, using the nearest point on the ground at the bottom of the frame as the near reference point and the nearest point on the barn roof (likely the lower edge of the roof) as my far reference point. This would tilt the plane of sharp focus just a bit. I've found that this tiny bit of tilt normally allows me to use a larger aperture than not using movements.

    That focus position after the tilt was applied, i.e., with the ground at the bottom of the frame and the edge of the roof both in focus would then become my "near" focus point; I would note the position of the standards on the camera bed/rail.

    Then I'd look for the farthest point from that plane to use as my "far" focus point. That would probably be where the ground meets the base of the tree line far left, or maybe the distant hill behind the trees. I'd check both of them, focus on whichever one was most distant and then note the position of the standards on my camera bed/rail (I have mm scales on all my cameras just for this).

    I'd then note the difference between the "near" focus point position and the "far" focus point position. Just for fun, let's say that it's 3 mm. I'd set the focus exactly halfway between the two extremes, that is, at 1.5 mm shorter than the "near" position.

    Then, I'd check the handy table I have taped to the side of my camera that would tell me that for a focus spread of 3 mm, I need to use f/32.2. I'd set my aperture to the closest setting to that depending on the shutter speed (since speeds are in whole stops, I might have to choose a slightly smaller aperture).

    Then "click."

    BTW, the fact that you're using a 75mm lens for the shots you're posting means that with these, there will be very little focus spread between near and far, likely a mm or less. So, you don't have real depth-of-field issues with that lens. Try checking near/far positions in such scenes with a 210mm or 300mm lens and you'll quickly get into focus spreads of 4-6 mm or more.

    Best,

    Doremus
    I reviewed your various posts. Let's take this one step at a time if that's OK with you. See picture below for annotations. If I understand correctly, you first focus on A and then tilt for B focus. Note the spot on the rail. Then refocus from A to C. Note the spot on the rail. Move the standard so the final focus is halfway between A and C on the rail. Pick the f stop from the setting chart.

    Some questions regarding this photo's adjustments:
    1. When you refocus to C from A, doesn't B tilt point go out of focus? Are you supposed to re-adjust it into focus?
    2. Should the procedure be different if you use asymmetrical tilts with the back standard vs. the more traditional approach of using the front stand for tilting with a few iterations?
    3. Let's say there a large tree extending from the bottom to top in the foreground on the right. Then I understand that tilting won't work. The top ofm the tree will be out of focus. So you have to use only DOF calculations with an appropriate F stop. Where would you put the center focal point?
    Attached Thumbnails Attached Thumbnails Focusing.jpg  

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