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Thread: All you ever wanted to know about depth of field and bokeh...

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    rpcrowe's Avatar
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    All you ever wanted to know about depth of field and bokeh...

    and a lot you never cared to know about "Schärfentiefe" or "Tiefenschärfe".

    This is an in-depth study of the above subjects from the Carl Zeiss Camera Lens Division...

    http://www.zeiss.com/c12567a8003b8b6f/embedtitelintern/cln_35_bokeh_en/$file/cln35_bokeh_en.pdf

    BTW: it is a pdf file 45 pages long.

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    Re: All you ever wanted to know about depth of field and bokeh...

    Start throwing mathematical formulae at me and I glaze over. I think that needs a quiet day with no disturbances to get to grips with.

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    rpcrowe's Avatar
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    Re: All you ever wanted to know about depth of field and bokeh...

    I agree! I just thumbed (if you can use that verb with a pdf document on a computer) through the article and decided that I would save it until I had several hours of free time and I was absolutely bored.

    Actually, I wanted to confirm or discount one of my thoughts about DOF. That thought is the depth of field in macro work is dependent on the image ratio and doesn't change with different focal lengths and camera to subject distances; as long as the image ratio remains the same.

    In other words, an image with a 1:1 image ratio has the same DOF if it were shot with a 50mm, 60mm, 80mm, 100mm, 150mm or 180mm lens as long as the image was shot at the same f/stop and with the same format camera. The reason that the format would make a difference is that the circle of confusion for one format is different from a smaller or larger format.

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    Re: All you ever wanted to know about depth of field and bokeh...

    Any in-depth discussion of depth of field apparently requires an in-depth discussion of the circle of confusion, which...well... always leaves me confused. I'll leave this stuff to you heavyweights who understand it.

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    Moderator Donald's Avatar
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    Re: All you ever wanted to know about depth of field and bokeh...

    Quote Originally Posted by Mike Buckley View Post
    I'll leave this stuff to you heavyweights who understand it.
    Doh!

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    Re: All you ever wanted to know about depth of field and bokeh...

    Quote Originally Posted by rpcrowe View Post
    Actually, I wanted to confirm or discount one of my thoughts about DOF. That thought is the depth of field in macro work is dependent on the image ratio and doesn't change with different focal lengths and camera to subject distances; as long as the image ratio remains the same.

    In other words, an image with a 1:1 image ratio has the same DOF if it were shot with a 50mm, 60mm, 80mm, 100mm, 150mm or 180mm lens as long as the image was shot at the same f/stop and with the same format camera. The reason that the format would make a difference is that the circle of confusion for one format is different from a smaller or larger format.
    For the 'image' to have the same 1:1 ratio (I assume you are meaning that the subject will be the same size on the sensor whether being taken with a 50mm or 150mm focal length lens) the DOF will be the same for each different focal length lens used. I had a quick look at a DOF calculator but this was also mentioned in an answer to a query I put up on another thread a while ago.

    I'm certainly no expert on this and when it comes to circles of confusion I'm totally lost but will be interested to hear other answers to your question.

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    rpcrowe's Avatar
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    Re: All you ever wanted to know about depth of field and bokeh...

    Grahame, you replied, "For the 'image' to have the same 1:1 ratio (I assume you are meaning that the subject will be the same size on the sensor whether being taken with a 50mm or 150mm focal length lens) the DOF will be the same for each different focal length lens used."

    I was pretty sure this is true, however, I could not find way to confirm it since I am reluctant to access DOFMaster website because of the posting that the site had been hijacked and was transmitting a virus...

    Mike, in the midst of the rather involved article on DOF I referenced there is an rather clear explanation of Circle of Confusion.

    However, I usually explain it in even more simple terms. A smaller format needs to be enlarged to a greater degree than a larger format. Therefore the image on the smaller format needs to be sharper that the image on the larger format to have the same degree of sharpness when enarged to equivalent size.

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    Re: All you ever wanted to know about depth of field and bokeh...

    Quote Originally Posted by rpcrowe View Post
    I agree! I just thumbed (if you can use that verb with a pdf document on a computer) through the article and decided that I would save it until I had several hours of free time and I was absolutely bored.

    Actually, I wanted to confirm or discount one of my thoughts about DOF. That thought is the depth of field in macro work is dependent on the image ratio and doesn't change with different focal lengths and camera to subject distances; as long as the image ratio remains the same.

    In other words, an image with a 1:1 image ratio has the same DOF if it were shot with a 50mm, 60mm, 80mm, 100mm, 150mm or 180mm lens as long as the image was shot at the same f/stop and with the same format camera. The reason that the format would make a difference is that the circle of confusion for one format is different from a smaller or larger format.
    Try this link http://berniesumption.com/photograph...f-field-table/ it tends to confirm your assumption.

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