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    DOF comparison between BMC and "Full Frame" (DSLR)
    #1
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    Ok so we know at this point what the crop factor is for most lenses which are coming from a full frame photography reference (2.31x)

    However, what interests me is some kind of chart or database which shows what happens to depth of field from one format to the next.

    An example, I believe I have heard Barry state that roughly what would be the equivalent of f1.4-f2 on the BMC would be equivalent in the depth of field of to f4-f5.6 on a full frame DSLR. (very roughly)

    From a practical standpoint, in considering the MFT mount vs. the EF, we know that the MFT would offer greater opportunites for faster lenses and shallower DOF for wide angle lenses.
    A chart like this at various F stops starting with say f0.95 would be very helpful in clarifying for me a decision as to the value of switching to the MFT.
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    #2
    Senior Member nickjbedford's Avatar
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    The depth of of field only changes because you have to use a wider focal length or move back to reframe your subject.

    I'm pretty sure the calculation is f-stop x crop factor = depth of field (equivalent f-stop) with same framing.

    So frame the same subject with two different focal lengths and your depth of field in terms of f-stop should be 2.3x smaller.

    I expect F2.8 to be approximately similar to F6.4. But in reality, I'm used to F2.8 on APS-C so in my experience of F2.8 it's more like F3.5.
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    #3
    Quote Originally Posted by nickjbedford View Post
    I expect F2.8 to be approximately similar to F6.4. But in reality, I'm used to F2.8 on APS-C so in my experience of F2.8 it's more like F3.5.
    This is important. In professional film, this is what every DoP is used to, as standard is Super 35, not full frame!
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    #4
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    http://www.tawbaware.com/maxlyons/calc.htm

    or http://www.abelcine.com/fov/

    you need to use them backwards, sort of!

    Of course if you have your own FF camera you could fo your own tests using cropping to create the BMC vision

    To 'match' images you would need to choose a wider lens on the BMC of course

    My feeling after experimenting with the H1, D3 and D80 is that DOF drops in an inverse square manner

    so to half the DOF you need to quadruple the sensor area

    personal conclusion - MFT is miles nicer than 1/3 and not far at all off s35/FF if you can get the lenses

    I would be interested to see is compared to S16 where you can get the lenses

    S
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    #5
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    Quote Originally Posted by Gabriel De Bourg View Post
    This is important. In professional film, this is what every DoP is used to, as standard is Super 35, not full frame!
    Not interested in entering into that polemic, thank you.
    Last edited by yoclay; 09-27-2012 at 08:15 AM.
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    #6
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    The Lens Equivalence / Diffraction Calculator is perfect for the job. Much appreciated Morgan_Moore!

    Important to note that for the FF reference, the dimensions we would be using are 36 x 20.3 (not 24mm)
    as that corresponds to the 16x9 crop for video.
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    #7
    Senior Member Willian Aleman's Avatar
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    Here is an interesting manual for Expoaperture2, a tool to calculate aperture, images sharpeness, focal length lens, hyper focal, circle-of-confusion.
    The manual has a historical and an extensive explanation of critical lens measurements as a tool for composition.

    Content:

    1. - An Introduction to Depth-Of-Field
    1.A. - Focus as a Compositional Tool
    1.B - Controlling Depth of Field
    1.C - Image Sharpness
    1.D - Permissible Circle-of-Confusion
    1.E - The Advent of Digital Cameras
    1.F Conclusion: Taking Advantage of Depth-of-Field in Your Photography
    2. - Using the ExpoAperture2 Depth-Of-Field Guide
    2.A - Distance Dial
    2.B - Focus Zone Dial
    2.C - Focal Length Dial
    2.D - f/stop and Circle-of-Confusion Dial
    2.E - Determining The Correct Aperture and Focal Point
    2.F - Determining Depth-of-Field for a Given Aperture and Focal Distance
    2.G - Determining Hyperfocal Distances
    2.H - Setting Apertures for Lenses with Focal Lengths Greater than 135mm
    2.I - Close and Macro Photography

    http://www.expoimaging.com/MediaFile...ions/EN_34.pdf

    ExpoAperture2 Depth-of-Field Guide
    http://www.expoimaging.com/product-d...of-Field_Guide
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    #8
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    A depth of field comparison database would be almost next to useless. Almost all lenses render out of focus areas differently, with wide ranging characteristics, colour and artefacts.

    Any 2.8 lens will give you plenty DOF control on the BMC's sensor (assuming your not using a WA). If you're shooting talking heads/narrative 2.8-4 is a great starting point for complete focus.

    I have the Nokton 25/0.95 and it requires a ninja to pull focus.
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    #9
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    Quote Originally Posted by itimjim View Post
    it requires a ninja to pull focus.
    With what camera?

    You are gonna be farther back for an equiv FOV with the bmc focus will not be the same?

    S
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    #10
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    To me this seems a very circular debate, and not massively productive on location.

    Comparing the camera you will be using on a shoot to a camera that you're not using seems somewhat pointless. Each camera has it's own strengths and weaknesses and you will be able to get great DOF out of the BMCC but you will have to position your camera and choose your lens according to what you want to shoot. (I've been getting lovely shallow DOF on 2/3 cameras for over a decade).

    Sure these tables and comparisons make interesting and informative reading but on a shoot that goes out of the window as you'll be working to get the best out of the camera (and sensor) that you have available within the limitations of your lens choice, the available light and the geography of the location.

    The biggest concern for the BMCC has always been can you get fast and wide in a confined space? IMO the Tokina 11-16 or various lens options for the MFT mount will give you that most of the time. If that doesn't work you either need to change camera, lens or location - probably never going to get super wide in a broom cupboard with the BMCC.

    You will get beautiful footage from the BMCC with it's own unique aesthetic when you play to its strengths. Similarly you can get beautiful shots from a 5D (or even an iPhone) when you play to those cameras strengths - but what you don't get with them is much (if any) latitude outside of their strength areas thanks mainly to a lousy codec. With RAW (or even ProRes) the BMCC will give you far more latitude even when not everything is hitting the sweet spot.
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