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Thread: Using DOF Calculations Bestly for Print Size

  1. #11

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    Re: Using DOF Calculations Bestly for Print Size

    Quote Originally Posted by Doremus Scudder View Post
    How else do you get those shots anyway?
    Many times Scheimflug helps a lot !!!

    If the close part of the scene is at the bottom and the far part is at the top then some tilt always helps to save some diffraction, or a lot of diffraction, or all diffraction effect in the IQ. Or we can play with defocus, selective focus is also a great resource, if one likes that.

  2. #12
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    Re: Using DOF Calculations Bestly for Print Size

    Quote Originally Posted by Tin Can View Post
    I have used DOF Master Calculator often, this one. https://www.dofmaster.com/dofjs.html

    Probably incorrectly as even I see problems in my small enlargements.
    I think the problem with DOF calculations, especially when using pure math to make them, is that it supposes the whole depth of focus area will be the same sharpness.

    Regardless of aperture, only one point in space is "in-focus" while the rest inside the DOF is supposedly "close enough." I've found DOF calculators or DOF markings on small-format lenses to often grossly underestimate the acceptable DOF in most situations (35mm lenses especially, as they usually suppose a 4x6 "jumbo print" IIRC). If a given focus point calculates to have everything in focus front-to-back, I would stop down an additional 1-2 stops to ensure this if working at the extremes, regardless of "diffraction."

    I also tend to reject the "1/3 in front, 2/3 behind" focus paradigm in many situations, especially with a strong foreground element. A foreground element inside the DOF and math claims should be "acceptably sharp" to me often seems unacceptably fuzzy on the negative - so focusing a bit closer and stopping down a bit more seems more effective. YMMV.
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  3. #13
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    Re: Using DOF Calculations Bestly for Print Size

    POINT taken!

    Thank you

    Quote Originally Posted by Corran View Post
    I think the problem with DOF calculations, especially when using pure math to make them, is that it supposes the whole depth of focus area will be the same sharpness.

    Regardless of aperture, only one point in space is "in-focus" while the rest inside the DOF is supposedly "close enough." I've found DOF calculators or DOF markings on small-format lenses to often grossly underestimate the acceptable DOF in most situations (35mm lenses especially, as they usually suppose a 4x6 "jumbo print" IIRC). If a given focus point calculates to have everything in focus front-to-back, I would stop down an additional 1-2 stops to ensure this if working at the extremes, regardless of "diffraction."

    I also tend to reject the "1/3 in front, 2/3 behind" focus paradigm in many situations, especially with a strong foreground element. A foreground element inside the DOF and math claims should be "acceptably sharp" to me often seems unacceptably fuzzy on the negative - so focusing a bit closer and stopping down a bit more seems more effective. YMMV.
    sin eater

  4. #14

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    Re: Using DOF Calculations Bestly for Print Size

    The DoF calculator app (by Jonathan Sachs) for the smartphone I use tells the CoC in each place of the field, so we know what optic performance remains at each spot we want to consider.

    Click image for larger version. 

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    There is also a Windows version

    http://www.dl-c.com/DoF/


    One thing it was useful to me to learn to balance diffraction vs DOF was making a practice with a (cheap) laser range meter and the smartphone app, without the camera, just taking a real scene, considering different apertures and focus distances, and then checking the CoC for the different spots.

    This is an interesting exercise because one learns to balance optical performance in the plane of focus vs the rest in the DOF.

  5. #15
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    Re: Using DOF Calculations Bestly for Print Size

    Pere, need exact name of app iOS
    sin eater

  6. #16

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    Re: Using DOF Calculations Bestly for Print Size

    Quote Originally Posted by Pere Casals View Post
    Many times Scheimflug helps a lot !!!

    If the close part of the scene is at the bottom and the far part is at the top then some tilt always helps to save some diffraction, or a lot of diffraction, or all diffraction effect in the IQ. Or we can play with defocus, selective focus is also a great resource, if one likes that.
    Pere,

    After 30+ years of LF, I'm adept at using movements to position of the plane of sharp focus in order to optimize my aperture. I even wrote an article on the subject for the now-defunct View Camera magazine. Still, there are times when, even after applying optimal movements, stopping down into the realm of diffraction degradation is the only solution to get the necessary depth-of-field for a particular scene (think very near/far with lots of verticals... you get it). In cases like that, e.g., when I'm forced to use f/45 with a 4x5 camera, it's good to know in advance just how large one can print before diffraction becomes too distracting.

    As far as defocus goes... it's not really my style.

    Best,

    Doremus

  7. #17
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    Re: Using DOF Calculations Bestly for Print Size

    Of course it depends on what / where you photograph, but things rarely fit inside the perfect Scheimpflug "wedge" at f/22 for me.
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  8. #18

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    Re: Using DOF Calculations Bestly for Print Size

    Quote Originally Posted by Corran View Post
    I think the problem with DOF calculations, especially when using pure math to make them, is that it supposes the whole depth of focus area will be the same sharpness.

    Regardless of aperture, only one point in space is "in-focus" while the rest inside the DOF is supposedly "close enough." I've found DOF calculators or DOF markings on small-format lenses to often grossly underestimate the acceptable DOF in most situations (35mm lenses especially, as they usually suppose a 4x6 "jumbo print" IIRC). If a given focus point calculates to have everything in focus front-to-back, I would stop down an additional 1-2 stops to ensure this if working at the extremes, regardless of "diffraction."

    I also tend to reject the "1/3 in front, 2/3 behind" focus paradigm in many situations, especially with a strong foreground element. A foreground element inside the DOF and math claims should be "acceptably sharp" to me often seems unacceptably fuzzy on the negative - so focusing a bit closer and stopping down a bit more seems more effective. YMMV.
    Corran,

    You're exactly right. One has to do test for one's own acceptable circle of confusion and do the math based on that. Using some one else's standards, especially the overly-optimistic ones from many manufacturers, just doesn't cut it. After one has done one's homework, the system is really reliable.


    "1/3 in front, 2/3 behind" is just wrong except at one, rather close-to-the-camera distance. At longer distances, 1/2 / 1/2 is more like it. Finding good "near / far" points and splitting the focus spread (based on your own standards) automatically adjusts for the different distances in front of and behind the plane of sharp focus. When using tilt/swing movements, the situation becomes more complicated; "near" and "far" can be "down" and "up," or "right" and "left." Visualizing where the plane of sharp focus is in a scene helps immensely when choosing focus points.


    Quote Originally Posted by Corran View Post
    Of course it depends on what / where you photograph, but things rarely fit inside the perfect Scheimpflug "wedge" at f/22 for me.
    Me neither! I think my most used aperture for 4x5 is f/32. It seems to me, that any scene that has significant near/far depth will require stopping down past the optimal aperture if you want everything sharp (why do you think the West Coast School chose the name "f/64" ?)

    Best,

    Doremus

  9. #19

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    Re: Using DOF Calculations Bestly for Print Size

    Quote Originally Posted by Doremus Scudder View Post
    After 30+ years of LF, I'm adept at using movements to position of the plane of sharp focus in order to optimize my aperture. I even wrote an article on the subject for the now-defunct View Camera magazine. Still, there are times when, even after applying optimal movements, stopping down into the realm of diffraction degradation is the only solution to get the necessary depth-of-field for a particular scene (think very near/far with lots of verticals... you get it). In cases like that, e.g., when I'm forced to use f/45 with a 4x5 camera, it's good to know in advance just how large one can print before diffraction becomes too distracting.
    Doremus, of course... but let me propose next: if we have to shot at f/45 then diffraction limits our image quality to 35lp/mm at extintion, so a better alternative is using a MF back (or camera) with a shorter focal that it would allow an slower film for the same shutter speed, we save film without any IQ loss...


    IMHO sometimes in a great LF shot we see how the photographer searched the right framing and angle to make shine the view camera taking, perhaps we may leave some kind of scenes for the smartphones...


    Quote Originally Posted by Tin Can View Post
    Pere, need exact name of app iOS
    Randy, sorry, this one is only released for windows and for android. Best bet would be taking an old/used/cheap android phone for that.

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