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Thread: Choice for the Circle of Confusion?

  1. #21

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    Re: Choice for the Circle of Confusion?

    Quote Originally Posted by Bob Salomon View Post
    Why do you keep reinventing the wheel? Photographers controlled DOF accurately and easily well before digital came about.
    Bob, at all I'm not saying that attachig a DSLR in the back is the way to adjust DOF in the field, just I'm saying that's a very useful exercise to learn very well that matter from direct view of the real effects. Me, I learned a lot about what matters and what not with this exercise.

    First hand, I can say that this way helped me to understand/learn easily and fast the DOF/diffraction effects.

    It is a WYSIWYG, as we stop we inmediately see in the monitor the blurring effect of diffraction in the focus plane, and the sharpening effect in the DOF, so it's useful to learn the trade-off and the good balance.




    Quote Originally Posted by Bob Salomon View Post
    Get your self the pocket Rodenstock and do it easily, no batteries, no electronics, no rulers needed!
    Well, this is very good advice, no doubt.

  2. #22

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    Re: Choice for the Circle of Confusion?

    I agree with Pere that looking at large format lenses with a high res DSLR can be a useful exercise. For example it showed me that the 180mm Renstock Sironar S 180mm at f/8 is as good as the native glass I have for the Sony A7RIII (42MP) at a pixel level. That goes against a lot of what I've seen published. The Nikon 180mm lens is also as good (as measurable by the test) in the center, but seems to have some field curvature as you move towards the edges. You can of course also see the effect of stopping down and resolution does indeed drop as you stop down, as we all know with out needing to test it.

    But I don't see much benefit to the test in a practical manner for composing large format photos, other than letting you know you want to use a large aperture that still meets your depth of field needs. If I know I need F/32 to get the whole subject in the acceptable DOF then that's what I need. I also know there will be upper limits to how large a print I can make that's "acceptably sharp". That balance is the heart of this thread.

    I really like the approach outlined in the article, https://www.largeformatphotography.info/fstop.html, linked by Doremus Scudder in answer #6. For me that's all I want to consider while shooting.

  3. #23
    Tin Can's Avatar
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    Re: Choice for the Circle of Confusion?

    It's get confusing as some wrote in this old LFPF thread.

    Bob often suggests the Rodenstock Depth of Field Calculator which is available at that link, but seemingly out of production back in 2007 as indicated in the early post.

    I cannot find out how big the circular slide rule is, one says it's made of plastic. Any thoughts on durability?

    I may have difficulty reading the fine print on the slide rule in the field.

    As I recall from my brief Sinar P experience there are scales on a P to use for deciding ideal focus directly on GG the near and far points.

    Does a Norma have this function also?

    The slide rule costs more than my reliable new Walmart iPhone SE which has zoom to read fine print enabling an App to be read anywhere, even in the dark.

    Plus, having the slide rule instructions seems very important.

    I grew up using slide rules...the only one I have now calculates compound interest and mortgages.

    So we ask for more discussion.

  4. #24

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    Re: Choice for the Circle of Confusion?

    Quote Originally Posted by Bob Salomon View Post
    Why do you keep reinventing the wheel? . . .

    There will always be an endeavor to integrate the new with the old. Even if a given effort isn't fruitful, at least different avenues are being explored. And, who's to say what other possibilities might not emerge?

  5. #25

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    Re: Choice for the Circle of Confusion?

    Quote Originally Posted by Larry Gebhardt View Post
    that looking at large format lenses with a high res DSLR can be a useful exercise
    It also can be useful to check exposure. If lacking a shutter tester we may set B position in the DSLR (that's in the back of the view camera) and firing the LF shutter, then comparing the image with the the LF shutter open in B and firing the DSLR. Also it can check the aperture calibration, and it would also work as a TTL spot meter for the view camera that accounts for bellows extension and lens transmission, working like a probe.

    Again this would not be much for the field, but it would be useful to check/adjust gear.



    Quote Originally Posted by Larry Gebhardt View Post
    I really like the approach outlined in the article, https://www.largeformatphotography.info/fstop.html, linked by Doremus Scudder in answer #6. For me that's all I want to consider while shooting.
    +1

    But I'd add using a DOF App in the smartphone and the pocket Rodenstock calculator, it can be found used.

  6. #26

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    Re: Choice for the Circle of Confusion?

    Quote Originally Posted by Tin Can View Post
    It's get confusing as some wrote in this old LFPF thread.

    Bob often suggests the Rodenstock Depth of Field Calculator which is available at that link, but seemingly out of production back in 2007 as indicated in the early post.

    I cannot find out how big the circular slide rule is, one says it's made of plastic. Any thoughts on durability?

    I may have difficulty reading the fine print on the slide rule in the field.

    As I recall from my brief Sinar P experience there are scales on a P to use for deciding ideal focus directly on GG the near and far points.

    Does a Norma have this function also?

    The slide rule costs more than my reliable new Walmart iPhone SE which has zoom to read fine print enabling an App to be read anywhere, even in the dark.

    Plus, having the slide rule instructions seems very important.

    I grew up using slide rules...the only one I have now calculates compound interest and mortgages.

    So we ask for more discussion.
    It is now called the Linos calculator as Rodenstock Precision Optical was sold to Linos and then Linos was sold to Qioptiq.

    The scale is about the width of a dress shirt pocket as the calculator easily fits in one, in its case. One side calculates DOF at several scales for 35mm to 810. So it can also calculate DOF for DSLR FF Cameras. It also calculates the angle of the camera to the subject.

    The opposite side calculates Scheimpflug for the same film sizes and also camera angles.
    Lastly the calculator will indicate how much exposure correction might be required, depending on the chosen image scale.

    The scales are printed in very legible type on the calculators and are easily readable even with my 78 year old eyes with or without my glasses.

    While it comes with a detailed instruction sheet the designer, Dr, Schön, numbered each step to do the calculation determination and even his some pictograms to show what each step is doing on the calculator.

    Unlike dragging a DSLR out with you to do the DOF the Linos weighs about 2 or 3 ozs and fits flat in your shirt pocket. In all the years that we distributed them we never had one wear out nor had we ever had to replace one. They are extremely durable and easily cleaned off, if necessary. Rodenstock also supplied them OEM for other European companies like Sinar and Linhof without reports of problems, save for people who didn’t read the instruction sheet. But simple, short telephone conversations fixed those problems.

  7. #27

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    Re: Choice for the Circle of Confusion?

    Quote Originally Posted by Pere Casals View Post
    It also can be useful to check exposure. If lacking a shutter tester we may set B position in the DSLR (that's in the back of the view camera) and firing the LF shutter, then comparing the image with the the LF shutter open in B and firing the DSLR. Also it can check the aperture calibration, and it would also work as a TTL spot meter for the view camera that accounts for bellows extension and lens transmission, working like a probe.

    Again this would not be much for the field, but it would be useful to check/adjust gear.





    +1

    But I'd add using a DOF App in the smartphone and the pocket Rodenstock calculator, it can be found used.
    It would seem that if you wanted to use a DSLR on a view camera as a spot meter then you would be constantly moving the view camera to meter different spots on the scene.
    It would be much easier to just use a spot meter in the first place.

  8. #28
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    Re: Choice for the Circle of Confusion?

    Good answer Bob. I like things that fit in a shirt pocket.

    My eyes used to focus on anything very close, such as a GG, but since my cataracts were removed and far sight 10 diopters lenses installed in both eyes, close up now requires at least 3X readers.

    And 20X loupe seems best, but I hate using my Nikon AF 50mm f1.4 as field loupe. It will get damaged.

    I am going to start another loupe thread.


    Quote Originally Posted by Bob Salomon View Post
    It is now called the Linos calculator as Rodenstock Precision Optical was sold to Linos and then Linos was sold to Qioptiq.

    The scale is about the length of a dress shirt pocket as the calculator easily fits in one, in its case. One side calculates DOF at several scales for 35mm to 810. So it can also calculate DOF for DSLR FF Cameras. It also calculates the angle of the camera to the subject.

    The opposite side calculates Scheimpflug for the same film sizes and also camera angles.
    Lastly the calculator will indicate how much exposure correction might be required, depending on the chosen image scale.

    The scales are printed in very legible type on the calculators and are easily readable even with my 78 year old eyes with or without my glasses.

    While it comes with a detailed instruction sheet the designer, Dr, Schön, numbered each step to do the calculation determination and even his some pictograms to show what each step is doing on the calculator.

    Unlike dragging a DSLR out with you to do the DOF the Linos weighs about 2 or 3 ozs and fits flat in your shirt pocket. In all the years that we distributed them we never had one wear out nor had we ever had to replace one. They are extremely durable and easily cleaned off, if necessary. Rodenstock also supplied them OEM for other European companies like Sinar and Linhof without reports of problems, save for people who didn’t read the instruction sheet. But simple, short telephone conversations fixed those problems.

  9. #29

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    Re: Choice for the Circle of Confusion?

    Challenge becomes translating the target circle of confusion into meaningful image elements for any given image to be made?


    Bernice

  10. #30

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    Re: Choice for the Circle of Confusion?

    Quote Originally Posted by Bob Salomon View Post
    It would seem that if you wanted to use a DSLR on a view camera as a spot meter then you would be constantly moving the view camera to meter different spots on the scene.
    It would be much easier to just use a spot meter in the first place.

    Of course, a good spot meter is a perfect choice, but I've not one.

    Using a DSLR/SLR in the back of a view camera is not for everyday, IMHO, but it allows to calibrate and check many things. In fact a (near for free) Nikon F65 in the back is a perfect Probe meter accounting all, lens transmission, aperture calibration, fall-off, bellows extension... It has a viewfinder so it's very convenient to navigate in the framing with the shift-rise.

    Also I can use the DSLR/SLR (+zoom) as if it was a Director's Scope that will tell if framing fits in the negative (Hor and Vert eq focals in the zoom), so when I haul the cambo 8x10 and my insanely heavy Bilora is just to shot, this way I avoid dragging around all those irons to find the good shot.

    Also, as DOF rules are the same, in the zoom I may place the same focal and aperture, and I can check what will happen in the 8x10 shot. So I focus to the intended distance, and with focus blocked I can explore and (DSLR) shot the rest of the field, by zomming in the rear screen of the DSLR I see how the rest will be compared to the object in the focus plane (if no tilt).

    I'm not saying that this has to be the regular procedure, at all, just it's useful for a learner like me.



    Quote Originally Posted by Bernice Loui View Post
    Challenge becomes translating the target circle of confusion into meaningful image elements for any given image to be made?
    At all, we can make top notch art with an smartphone in auto mode.


    An artist may take advantage from softness, from sharpness or from both at the same time. But there is nothing wrong in mastering DOF management, if one wants that.

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