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How will the depth of field compare to a Canon t2i or similar cropped frame DSLR's?

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  • How will the depth of field compare to a Canon t2i or similar cropped frame DSLR's?

    Will it be nearly as shallow or will it be similar to a Canon xl2?

    Also whats the crop form on the BMC, I'm sure these answers are all over this thread and I'm simply overlooking it.

    If we use 50mm will it remain 50mm?

  • #2
    use the calculator from abelcine

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

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    • #3
      If you compare it to 35mm film it is only 60% less angle of view or 60% longer lens. If it is a 50mm lens for 35mm film then it will be an 80mm lens on the BMDCC. Just look multiply the current lens you have by 1.6 and that will be your lens size.

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      • #4
        It will not be as shallow as a t2i, and it won't be anywhere near as deep as an XL2. In reality it'll be about halfway inbetween them.

        The t2i has a 22mm sensor. The XL2 has about a 6mm sensor. Halfway between those two would be 14mm, which is almost the same size as the BMC sensor: 15.6mm.

        There is no format that has the same size as the BMC (and therefore, the same DOF characteristics). The closest format out there would be Super16, at 12.4mm wide, but the BMC will be a little shallower than Super16. If you're familiar with the GH2, the BMC will not be as shallow as the GH2, but it'll be about halfway between a GH2 and Super16.

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        • #5
          Originally posted by Barry Green View Post
          It will not be as shallow as a t2i, and it won't be anywhere near as deep as an XL2. In reality it'll be about halfway inbetween them.

          The t2i has a 22mm sensor. The XL2 has about a 6mm sensor. Halfway between those two would be 14mm, which is almost the same size as the BMC sensor: 15.6mm.

          There is no format that has the same size as the BMC (and therefore, the same DOF characteristics). The closest format out there would be Super16, at 12.4mm wide, but the BMC will be a little shallower than Super16. If you're familiar with the GH2, the BMC will not be as shallow as the GH2, but it'll be about halfway between a GH2 and Super16.
          Interesting. I wasn't aware the sensor was so small. I was under the mistaken impression that the DOF would be closer to the AF100.

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          • #6
            Originally posted by Jesus View Post
            ... Also whats the crop form on the BMC ...
            In addition to the info previously posted, the BMCC’s crop factor is reported to be about 1.6 compared to S35 motion picture cameras, and about 2.3 compared to a full-frame digital still camera. The first comparison is perhaps the more meaningful one for filmmakers.

            So, for example, mounted on a BMCC the FOV of a Tokina 11-16mm f2.8 DSLR zoom lens at its wide end is about the same as a 18.5mm lens on a S35 camera. If that’s not wide enough, one might use the slower but wider Sigma 8-16mm DSLR zoom lens for a FOV comparable to an 13mm lens on a S35 cam. There are many other lenses, including some cinema-style primes, that can also be used on a BMCC.

            On a related note, someone noted that the BMCC’s shape allows it to be backed up into a corner or against a wall to yeild as wide a view as possible. Obviously you must leave room to poke its LCD touchscreen with your finger, but it’s an interesting thought. Cheers.
            www.peterdv.com
            Blog: http://HereForTheWeather.wordpress.com

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            • #7
              Use this for AOV comparison against any sensor/negative size you want http://www.abelcine.com/fov/

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              • #8
                put a lens on yer t2i and leave it at f5.6 and you're about there on a bmc at f2.8
                edit: give or take 1/3 of a stop
                edit: corrected on post 12
                Last edited by J Davis; 08-14-2012, 07:24 AM.
                J.Davis
                jdMAX.com

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                • #9
                  Originally posted by J Davis View Post
                  put a lens on yer t2i and leave it at f5.6 and you're about there on a bmc at f2.8
                  edit: give or take 1/3 of a stop
                  Really? I'm not really sure, but 2 stops seems too much to me... How do you get to such calculations?
                  Film Director
                  enricoatwork.com

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                  • #10
                    the t2i is confusing, because it introduces a crop factor itself, which is 1,6 compared with a 35mm Full frames sensor (or negative) on PHOTO cameras.
                    The BMC camera is said to be crop factor 2.2 (or 2.3) for canon mount lenses (35mm photo sensor).
                    I'd say f2.8 on the BMC is about the dept of field of f4.0 on the t2i

                    To go from the crop factor of the t2i to the BMC, it's 2.2 divided by 1.6 = 1.375, lets say 1.4 (because 2.3 is possible)
                    2.8 x 1.4 = 3.92, so yeah let's say f4.0

                    of course, the dept of field doesn't REALLY change. The image stays the same but is cropped. That's ALL.
                    The dept of field will get larger when you take a step back to get the same stuff in the image (field of view) as on the t2i.
                    If you stay on the same spot with your BMC, technically, the dept of field REDUCES, because those blurred circles (COC) are getting bigger relative to your frame.

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                    • #11
                      the depth of field does change in practical use ... the reason why? You are now at a shorter focal length to get the same field of view
                      J.Davis
                      jdMAX.com

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                      • #12
                        Originally posted by rheex View Post
                        Really? I'm not really sure, but 2 stops seems too much to me... How do you get to such calculations?
                        Thanks sir you are correct. Was a tired and early a.m. post where my mind was thinking the bmc is like the old proposed 2/3 scarlet. Well it is in res but not in size, the bmc is 150% bigger. I recalculated the dof difference would be f2.8 on a t2i is roughly equivalent to an f3.5 / f4 split with the same lens on the bmc
                        J.Davis
                        jdMAX.com

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                        • #13
                          I agree:
                          "The dept of field will get larger when you take a step back to get the same stuff in the image (field of view) as on the t2i."
                          I guess you are right that, indirectly, DOF does change in the end result.

                          Dept of field is not affected by changing focal length as long as you keep the same field of view BTW.
                          If you have a zoom lens, and you change distance to the subject, but keep the field of view and aperture the same, the DOF will stay the same, regardless of the focal length you set the zoom in. (the SIZE of the background relating to the subject will change, though).
                          So a 20mm and a 100mm will have about the same dept of field if the framing is identical. It's just that you would need to get really close with a 20mm to match a closeup from a 100mm.

                          This is why I can get an incredibly small dept of field with my Ricoh GRD's 8mm lens. It's because it can focus as close as 1cm.

                          So same framing plus same aperture = same dept of field regardless of the lens.
                          If you want shallow dept of field, then the downside of the BMC Camera is that there are no really fast ultra wides, it's too hard/expensive to make them. For very long lenses, the BMC can provide a shallower dept of field then full frame. It's not very useful in reality, though.

                          Anyway, to understand the result on the BMC Camera best, is to simply take a photo from a t2i camera, and crop it to the BMC size. That is the ONLY change that will occur.

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                          • #14
                            Originally posted by traviswears View Post
                            Interesting. I wasn't aware the sensor was so small. I was under the mistaken impression that the DOF would be closer to the AF100.
                            It is certainly closer to the AF100 than it is to a t2i. The AF100 sensor is 17.8mm wide. The t2i is 22.3mm wide. The BMC is 15.6mm wide.

                            Compared to the t2i, the BMC has a crop factor of about 1.43; compared to the t2i the AF100 has a crop factor of about 1.25.
                            Compared to the AF100, the BMC has a crop factor of about 1.15.

                            It's not that the BMC sensor is very small, it's still way bigger than a 2/3" sensor.

                            The t2i's sensor is about 264 square mm.
                            The AF100's sensor is about 178 square mm.
                            The BMC's sensor is about 137 square mm. So it's about 50% the size of the t2i, and about 75% the size of the AF100.

                            It's bigger than S16 film (which is about 93 square mm). So I guess it's fair to say the BMC sensor is about halfway between S16 and Af100. It's not going to be hyper-shallow, but it's way bigger than S16 and with a very fast lens you will be able to get some nice shallow DOF shots with it.

                            Continuing with the prior comparisons, the XL2's sensor is about 5.3 x 3, so about 16 square mm. Halfway between a t2i (264) and XL2 (16) would be 140 square mm. And the BMC is 137 square mm, so ... yes, it's pretty much exactly halfway between an XL2 and a t2i.

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                            • #15
                              For the non technicals:

                              50mm on a t2i should be the same field of view as 35mm on a BMC.

                              So if you have a BMC at 35mm f2.8
                              and a t2i at 50mm f2.8
                              both filming the same scene showing the same field of view, the difference
                              between the two is the dof.

                              The t2i , 50mm f2.8 dof , shallower
                              The BMC , 35mm f2.8 dof , deeper

                              Same scene, same field of view
                              J.Davis
                              jdMAX.com

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