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Thread: Tilt and tall objects.

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    Senior Member Pemihan's Avatar
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    Tilt and tall objects.

    I recently got my Cambo SK 120mm converted into a T/S mount and am having some trouble getting the results I want.

    The image below is made with about 4.6 degrees tilt and focus set to about 21 meters at f11.
    The ground is perfectly in focus from front to back but the top of the buttes in the background are kinda soft.

    I'm having a little trouble to understand everything that is at play. I mean I got the basic but where should I put the focus in order to make the sharpness wedge as tall as possible?
    My camera is about 150 cm above ground, so 4.6 degrees tilt should be allright?
    Would it be better to shoot at f16 or higher?

    Thanks
    Peter

    Last edited by Pemihan; 14th October 2013 at 09:27.
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    Administrator, Instructor Guy Mancuso's Avatar
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    Re: Tilt and tall objects.

    Rule of thumb for every 30mm of a lens than use 1 degree of tilt at a normal height of like 5 foot eight inches. Here one of two things is off. Too a much tilt and your focus point is off. Here is where focus mask on a IQ is your friend. For focus and Ed just showed me on the work shop put the infinity mark at the F8 mark. We did a tilt test with 4 tech cams with a 40,43,47 and another with a 40. But our test was 2ft off the ground front standard tilting forward with a boardwalk as our subject. Our tilt was about 3 degrees but our test was with IQ backs so it was easy to see what we where doing not to mention the zoom feature. I processed it yesterday and it's pretty amazing how dead on we where. But our infinity distance was soft a little as well. But we where pushing it pretty hard. Now I heard in the past that with a digital back should not go past about 4 degrees. Now that is something I have not tested and maybe that is the issue is you took it to far. I'll let others weigh in as I'm not a expert on tilt. Everything else yes but tilt does confuse me sometimes. LOL

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    Member weinlamm's Avatar
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    Re: Tilt and tall objects.

    Hello Peter,

    stop down should be necessary - even with longer lenses. Here is an example from me; f11, 45mm, nearly 5 degrees tilted:



    You can see it's everything sharp the street down - but the houses roofs or the lantern...
    I stoped down a little bit more (first f16, then f22) and then it was better. I think this should be something you should do, too.

    But perhaps your scene is something where you could shoot without tilt. But it depends on what you want to show exactly.
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    Re: Tilt and tall objects.

    Quote Originally Posted by Pemihan View Post
    I recently got my Cambo SK 120mm converted into a T/S mount and am having some trouble getting the results I want.

    The image below is made with about 4.6 degrees tilt and focus set to about 21 meters at f11.
    The ground is perfectly in focus from front to back but the top of the buttes in the background are kinda soft.

    I'm having a little trouble to understand everything that is at play. I mean I got the basic but where should I put the focus in order to make the sharpness wedge as tall as possible?
    My camera is about 150 cm above ground, so 4.6 degrees tilt should be allright?
    Would it be better to shoot at f16 og higher?

    Thanks
    Peter

    Hi, In this case I would dial down the tilt a bit and focus at infinity. If you do not have a way of checking focus like with an IQ back then it is always best to take a few shots with different tilt inclinations.

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    Re: Tilt and tall objects.

    With tilts larger than say 3 degrees it's often hard it get all in focus without significant stop down. Long lenses require larger tilts. Up to 60mm or so I usually find a solution, but for longer lenses it's often required to compromise a bit, stopping down more, letting something be a little bit out of focus or stack.

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    Senior Member stngoldberg's Avatar
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    Re: Tilt and tall objects.

    I have the sk120 mounted on an Arca r3mdi lens board and shoot often with 4 degrees of tilt.
    For a scene like the one you used as an example, I would focus at a distance of at least one third from front to back of the image.
    I have discussed focus on this lens with Rod Klukas from Arca and he advised that it is often necessary to shoot at f16 to insure sharpness, especially on an image with is much area
    Stanley

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    Senior Member Pemihan's Avatar
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    Re: Tilt and tall objects.

    Thanks guys..

    I went out today and did some testing based on your input and the thing Guy mentioned about putting the infinity mark at the f8 mark actually works pretty well... that translates to setting the focus at 15 meters on the SK 120.
    I also tried setting it at 30 meters which makes the foreground a little better (in some ways) but made the far objects slightly softer.
    I set aperture at f16 and the tilt around 4.5 degrees.
    I'll do some more testing the next couple of days...

    Peter
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    Re: Tilt and tall objects.

    You might find my article on landscape focusing useful: How to focus a landscape scene it's a bit long though. The key concept I use in these type of scenes is "dof height", ie how much the wedge spans on the sensor at infinity. I see in the scene about how many mm I need and then look in a table what aperture I need for a certain tilt (dof height is same regardless of focal length).

    And the amount of tilt I can also get from a table depending on distance to ground and focal length.

    When getting used to tilting one can work much from experience, ie see directly on the scene what's possible to do and not.
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    Senior Member alajuela's Avatar
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    Re: Tilt and tall objects.

    Quote Originally Posted by torger View Post
    You might find my article on landscape focusing useful: How to focus a landscape scene it's a bit long though. The key concept I use in these type of scenes is "dof height", ie how much the wedge spans on the sensor at infinity. I see in the scene about how many mm I need and then look in a table what aperture I need for a certain tilt (dof height is same regardless of focal length).

    And the amount of tilt I can also get from a table depending on distance to ground and focal length.

    When getting used to tilting one can work much from experience, ie see directly on the scene what's possible to do and not.
    Amazing essay - really good

    Phil

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    Subscriber and Workshop Member MGrayson's Avatar
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    Re: Tilt and tall objects.

    Torger,

    That's the best presentation of geometric optics I've ever seen. The mathematics of focus isn't particularly complicated (as mathematical models go), but your article shows the difference between simply presenting some facts and making them them truly usable.

    Bravo, and thank you.

    --Matt

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    Senior Member Pemihan's Avatar
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    Re: Tilt and tall objects.

    That is a very useful article Torger, thank you very much.

    Peter

    Quote Originally Posted by torger View Post
    You might find my article on landscape focusing useful: How to focus a landscape scene it's a bit long though. The key concept I use in these type of scenes is "dof height", ie how much the wedge spans on the sensor at infinity. I see in the scene about how many mm I need and then look in a table what aperture I need for a certain tilt (dof height is same regardless of focal length).

    And the amount of tilt I can also get from a table depending on distance to ground and focal length.

    When getting used to tilting one can work much from experience, ie see directly on the scene what's possible to do and not.
    Peter
    My website

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