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Thread: DOF vs Tilt

  1. #1

    DOF vs Tilt

    I am an amateur film photographer. I have had my own darkroom in my house for 20 years and have always been a dedicated film user. I have just made the leap this week to LF, having purchased a 4x5 field camera. I am learning tilt, shift, etc (Thanks LF Forum and YouTube).

    For years I have shot a fully manual medium format camera so I use and understand Depth of Field. In the last few weeks, I have read numerous articles about Large Format cameras and the use of tilt for landscape shots to bring fore and background into focus. My question is this: Why not just use DOF of the large format lens and just leave the Large Format camera “zeroed out”, ie - no tilt? Setting it on f64 will surely give sharp detail from foreground to background in the scene.

    Thanks for the input.

    Charlie

  2. #2

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    Re: DOF vs Tilt

    Tilting or swinging lets you control the plane of sharp focus. Depth of field is the range of ACCEPTABLE sharp focus in front and behind the point of sharp focus.
    So when you do a tilt or a swing you modify the plane of sharp focus, stopping the lens down increases the depth of acceptable sharp focus in that plane.
    When you stop the lens down as far as 64 you will not get sharp results because of diffraction. Most 45 lenses are diffraction limited to f22.

    Since DOF runs normally 1/3rd towards the camera from the point focused on and 2/3rds away from that point the first thing you need to learn is where to focus to maximize your depth of field. If you are doing macro then the DOF is 50/50 from the point focused on.

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    Re: DOF vs Tilt

    Quote Originally Posted by cmcdarris View Post
    Setting it on f64 will surely give sharp detail from foreground to background in the scene.
    All too often it doesn't, and that is part of the challenge of shooting large format.

    With 4x5, normal and longer lenses cannot get a very near foreground and infinity background in simultaneous focus simply by stopping down, even to f/64. You either need to decide which portions of your composition can go out of focus, or apply movements (assuming they work for the scene) to optimize the plane of focus so less stopping down is necessary. Depth of field becomes even more limited if you migrate to larger LF formats.

    Additionally, stopping down to f/64 will noticeably soften your image due to diffraction, assuming you are enlarging and not contact printing (although some folks don't print large enough for this to matter). F/64 also means slower shutter speeds, making camera shake, subject movement or film reciprocity failure potential issues.

    Since you already have your LF camera, I suggest applying the f-stop selection technique described in this article and experimenting with how much stopping down works for you, given your shooting style and preferred choice of subjects:

    http://www.largeformatphotography.info/fstop.html

    Many folks new to LF are surprised by how much stopping down is required to get everything into acceptable focus!

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    ic-racer's Avatar
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    Re: DOF vs Tilt

    Quote Originally Posted by cmcdarris View Post
    Setting it on f64 will surely give sharp detail from foreground to background in the scene.
    ??

  5. #5

    Re: DOF vs Tilt

    Quote Originally Posted by ic-racer View Post
    ??
    Regarding medium format cameras and looking at a Depth of Field calculator (or just using the distance markings on my medium format lens), I can see that a landscape composition with an 80mm lens, subject 50 feet away, and lens at f22 yields a Depth of Field from 8 feet to infinity.

    Considering a Large Format lens, I was just assuming it would work the same, as the DOF Calculator shows a 150mm LF lens (comparable to an 80mm MF lens) focused at a subject 50’ away and set of f64 yields a DoF of 9 feet to infinity.

    Many thanks to the above responses, as I see there is more to consider with Large Format lenses.

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    Re: DOF vs Tilt

    Quote Originally Posted by cmcdarris View Post
    Regarding medium format cameras and looking at a Depth of Field calculator (or just using the distance markings on my medium format lens), I can see that a landscape composition with an 80mm lens, subject 50 feet away, and lens at f22 yields a Depth of Field from 8 feet to infinity.
    In the instructions for an earlier Hasselblad Super-Wide they made it clear that if one were to make particularly great enlargements, he should choose (at least) one stop smaller than the lens' guide. I agree, with experience making 40x40" enlargements. Sorry I do not have the full image here.

    Very much of perceived DOF depends upon viewing distance.
    .

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    Re: DOF vs Tilt

    Quote Originally Posted by cmcdarris View Post
    Regarding medium format cameras and looking at a Depth of Field calculator (or just using the distance markings on my medium format lens), I can see that a landscape composition with an 80mm lens, subject 50 feet away, and lens at f22 yields a Depth of Field from 8 feet to infinity.

    Considering a Large Format lens, I was just assuming it would work the same, as the DOF Calculator shows a 150mm LF lens (comparable to an 80mm MF lens) focused at a subject 50’ away and set of f64 yields a DoF of 9 feet to infinity.

    Many thanks to the above responses, as I see there is more to consider with Large Format lenses.
    Not quite. The circle of confusion for 45 is different then the CoC used for medium format. Since the film size is larger the film needs less enlargement for 45. Conversely the CoC for 35 is simarly different then MF or 45. There are pocket calculators to compute DOF as well as Scheimflug for formats from 35 to 810 like the Rodenstock/Linos one.

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    Re: DOF vs Tilt

    What enlargement factor or print size does your depth of field calculator assume? Often the depth of field markings on small and medium format lenses assume an 8x10 inch print size. If you are printing larger than that, then you will need more stringent calculations.

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    Re: DOF vs Tilt

    Quote Originally Posted by Bob Salomon View Post
    Not quite. The circle of confusion for 45 is different then the CoC used for medium format. Since the film size is larger the film needs less enlargement for 45. Conversely the CoC for 35 is simarly different then MF or 45. There are pocket calculators to compute DOF as well as Scheimflug for formats from 35 to 810 like the Rodenstock/Linos one.
    If the OP is using http://www.dofmaster.com/dofjs.html as his DOF calculator, then it's already taken into account the difference in the CoC's between the two formats.

    Edit: I don't know what he's using, but in http://www.dofmaster.com/dofjs.html, the 4x5 calculations for f64 are right, but the 6x6(?) calculation for f/22 are different--the markings on his lens aren't quite accurate to the caculator...

    Additionally: for both formats, focusing at 50ft is unnecessary since the hyperfocal distance is much closer than that. If you open up a 4x5 lens to f/32, you can focus at 23.6ft and get everything in focus from 11.8ft to infinity.

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    Re: DOF vs Tilt

    Quote Originally Posted by MAubrey View Post
    If the OP is using http://www.dofmaster.com/dofjs.html as his DOF calculator, then it's already taken into account the difference in the CoC's between the two formats.

    Edit: I don't know what he's using, but in http://www.dofmaster.com/dofjs.html, the 4x5 calculations for f64 are right, but the 6x6(?) calculation for f/22 are different--the markings on his lens aren't quite accurate to the caculator...

    Additionally: for both formats, focusing at 50ft is unnecessary since the hyperfocal distance is much closer than that. If you open up a 4x5 lens to f/32, you can focus at 23.6ft and get everything in focus from 11.8ft to infinity.
    You can open up a lens to, say, 5.6 but you would stop down a lens to f32. But on 45 that would also be in diffraction. Most lenses for 45 perform optimally at f22.

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