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Ursa Mini Pro at 1600 ISO vs Red Gemini at 500 ISO

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  • Ursa Mini Pro at 1600 ISO vs Red Gemini at 500 ISO

    Recently had the opportunity to have these cameras side by side on set. Talent was lit with a 800w Joker modified with a Profoto Beauty Dish a few feet away from the talent. I was incredibly surprised that I had to push the Ursa Mini Pro to 1600 ISO, wide open on a 24-70 at 2.8 in order to get a well exposed image. (Face is Grey/pink on False Color)

    From the same distance, two RED Geminis were at 500 ISO and a 6.3 aperture on Cooke primes. 6.3!! Is there really that big of a disparity between the two sensors? The ISO difference I can understand, but the f-stop difference is completely mind blowing. This is a 800w Joker we are talking about.

    And p.s - no, the ND filters were not active. I double checked them in disbelief. I never really cared for camera comparisons but this was an eye opener.

  • #2
    That doesn't sound right. Just a few days ago I shot some interviews with my UM46k and Tokina Cinema 50-135 T3.0.
    It was lit by a Rayzr7 300Watt daylight LED through a softbox, 2 meters away. I had the aperture closed down to T5.6 and the ISO at 200, shutter was 180°. Filmed at 25fps.

    Are you sure that the UMP had the same shutter setting as the REDs? I mean you saw an almost 4 stops difference. If that would be correct, then ISOs would have absolutely no meaning. It is normal that ISO 400 differs from camera type to camera type - but certainly not by 4 stops.

    Or maybe did the UMP lens have an ND or polarizing filter mounted onto the front?
    Happened to me, when I forgot the filter on a lens and put the lens onto the camera, wondering why the preview looked so dark compared to what I'd expected it to look like.

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    • #3
      No filter. Both cameras were at filmed at 60 fps
      .. thanks for confirming my suspicion that something is wrong though.

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      • #4
        You could examine the metadata of your UMP footage - the camera logs every setting used. It should show you the ISO, shutter speed, WB, lens aperture (except for manual lenses without metadata transmission), internal ND filter setting.
        Maybe there lies the answer hidden somewhere.

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        • #5
          And - is it maybe possible you mis-read the ISO setting on the RED Gemini? Could it have been set to LL-Mode at ISO 5000?

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          • #6
            Originally posted by Robert Niessner View Post
            You could examine the metadata of your UMP footage - the camera logs every setting used. It should show you the ISO, shutter speed, WB, lens aperture (except for manual lenses without metadata transmission), internal ND filter setting.
            Maybe there lies the answer hidden somewhere.
            I will check over the weekend. I have the camera in question as well as a Bmpcc4k with an XLspeedbooster - perhaps there's a way to accurately test values when compared side by side and seeing what exactly the difference is between the two.

            And no, definitely not- The geminis were at 500 iso for sure. It could be a bad sensor on the ursa pro.

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            • #7
              Appreciate all the input so far rob!

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              • #8
                Yes something is VERY wrong there. Some mistake must have happened OR that Ursa mini pro is defective. I've shot with a Scarlet W and my UMP g2 side by side with the same settings and the images were very identical apart from a bit of colour shift. I know you shot on with a Gemini but point is the differences should not be mind bogglingly different as in this case.
                Darren Scott
                Freelance Director/Director of Photography


                https://vimeo.com/jambredzvisions/videos

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                • #9
                  Are you sure it was wide open on the ursa? I once had the same on a Arri , the camera showed it was at 2.8 but it wasn’t. I had to open and close the apature on a sigma 18-35mm en voila it suddenly was at 5.6. Maybe a bug!

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                  • #10
                    Yeah something is definitely wrong. Even if you ignore the Geminis, a Joker 800 20 feet from talent with the super wide lens throws ~160fc, putting you in T8 territory for your exposure settings. I imagine the beauty dish much closer would throw even more light. So yeah, that's baffling, to say the least.
                    Aaron Lochert

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                    • #11
                      Four stop difference? No way, I meter frequently and personal taste aside BM cameras land where they’re supposed to. I’ve never shot Red, I’d wager they’re close as well. Somewhere, something isn’t reporting correctly. If you meter it will be simple to isolate which camera is reporting incorrectly.

                      Good Luck

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                      • #12
                        I once tested the BMP 4,6K against the Red Scarlet and they were very close. I'd also assume a basic flaw in the test mentioned here.

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                        • #13
                          Can you check that all ND filters in the unit are different, and that clear is actually clear?
                          Blackmagic Design
                          My BMD LUTs.

                          **Any post by me prior to Aug 2014 was before i started working for Blackmagic**

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                          • #14
                            Adding in my 2 cents - my Gemini is significantly "darker" to my eye when at the same ISO to other cameras.

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                            • #15
                              I had this happen with my UMP Sigma 18-35 and BMPCC 6K with a Canon CNE18-80. 6K was 1200 ISO @f5 and higher while UMP had to be 1600 @ f1.7 to get equal exposure. I assumed something was wrong with the lens and I wasn't actually anywhere near f1.7...

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