Thread: 4.6k Sensor Checklist

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  1. #1 4.6k Sensor Checklist 
    So I took the plunge and pre-ordered the Ursa Mini 4.6k Pro...I know... I know... But I've liked some of the footage I've seen come off the Blackmagic 4.6k sensor and with the "must-have" (for MY kind of work) add-ons to the Pro version I thought it was time to give Blackmagic a shot.

    What I was hopping to do was compile a check list of things to do to ensure I did in fact receive a "good sensor" while I still have the option to return or exchange it. So I appreciate any info, tips, etc. anyone with firsthand experience with the sensor can give not just myself but anyone scouring the forums and websites for info.
    Last edited by digitalinnovations; 03-07-2017 at 05:57 PM.
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  2. #2  
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    Quote Originally Posted by digitalinnovations View Post
    So I took the plunge and pre-ordered the Ursa Mini 4.6k Pro...I know. I know. I've liked some of the footage I've seen come of the Blackmagic 4.6k sensor and with the "must-have" (for MY kind of work) add-ons to the Pro version I thought it was time to give Blackmagic a shot.

    What I was hopping to do was compile a check list of things to do to ensure I did in fact receive a "good sensor" while I still have the option to return or exchange it. So I appreciate any info, tips, etc. anyone with firsthand experience with the sensor can give not just myself but anyone scouring the forums and websites for info.
    Thanks for making this post. I, too, ordered a pro and was wondering if I'd miss anything that QC didn't catch.
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  3. #3  
    - Vertical line FPN in the shadows at ISO 800. A little can be expected, a lot should not.

    - Crosshatching FPN -- if you see any, return. It is possible to get a sensor without any, and it's better to pursue that than to use the black shading calibration to *mostly* remove it.

    - Excessive magenta vignetting at f/5.6. I haven't seen a 100% clean sensor, but I've seen a terrible one (about 33% of image was tinted), a very clean one (~15%), and an almost invisible one (~5%).
    Shooting random videos on the 4.6k:
    https://vimeo.com/stephenplusplus
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  4. #4  
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    Yeah it would be GREAT to see someone shoot an evenly lit white wall, with the Sigma 18-35mm lens set to f/8 and 35mm. Id love to see DNGs (not compressed DNG) and if you have to set exposure, use the shutter angle to do it?

    I do wonder if the mini 4.6k Pro has the exact same sensor, or whether this magenta vignetting issue will be mitigated. Very interesting. Anyone who can share those DNGs, I would truly appreciate it!
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  5. #5  
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    Quote Originally Posted by stephenplusplus View Post

    - Excessive magenta vignetting at f/5.6. I haven't seen a 100% clean sensor, but I've seen a terrible one (about 33% of image was tinted), a very clean one (~15%), and an almost invisible one (~5%).
    They all have magenta vignette, I wouldn't even check for it. I did, and it depressed the hell out of me and a didn't use my camera for three months. If you shoot a white wall and get nothing it's clean by BM's standards - however all lenses (I get it with the 24, 35, and 50 leica R's I use the most from f4 and upwards, a contax 28 i tested had it to a terrible degree, a tokina 11-16 was as close to clean as I've seen) will exhibit it to some degree if you look closely enough. So maybe just do the white-wall-no-lens test and be done with it. It really has very little effect in everyday use unless you shoot a lot of landscapes at small f-stops.

    I have yet to see FPN in something a actually shot to use with ok amounts of light, Im sure I can bring it out if I want to, but after the magenta-test depression I had, I really prefer to be blissfully ignorant. Also to be fair the one production I've done on the Alexa also had FPN in a severely underexposed scenen. If you want to shoot in the dark, get a Sony cam instead.
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  6. #6  
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    Quick question, when buying a blackmagic ursa mini seconhand, is there a way to view the amount of hours the ursa mini has been used/running/shooted with?

    Thanks!
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  7. #7  
    Quote Originally Posted by yxfilm View Post
    They all have magenta vignette, I wouldn't even check for it.
    It's something that varies from "holy moly" to "oh, that's not so bad," so I still think a new buyer should judge for themselves if they will be bothered by it while they can still exchange or return it.

    Quote Originally Posted by yxfilm View Post
    If you want to shoot in the dark, get a Sony cam instead.
    Your exact thoughts on this are repeated a lot, but as the former owner of 2 4.6ks with terrible FPN and 1 with very acceptable FPN, it's not an opinion-- there are simply cameras with better sensors than others.
    Last edited by stephenplusplus; 03-10-2017 at 05:39 PM.
    Shooting random videos on the 4.6k:
    https://vimeo.com/stephenplusplus
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  8. #8  
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    Like all tests, best you also consider real world scenarios. Don't just look at the screen, shoot footage, put it into Resolve, GRADE IT and then look at it in the distribution formats you plan to render too...ie not the resolve viewer.

    If you look in FILM (log) you can often see a lot of issues that won't be there by the time you grade the image.

    If you shoot a chart for aliasing you'd get the impression the camera had a crippling problem. But in the real world, it rarely presents in that way. As well as shooting the "tests" also shoot the way you'd normally shoot a subject. The best way to really test of course is by shooting a project. It also then tests things you'll never think of like, do you accidentaly hit the power off switch, are you finding it easy enough to change the iris....

    JB
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  9. #9  
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    Last edited by rick.lang; 03-10-2017 at 04:57 PM.
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  10. #10  
    Thank you all for the tips / things to look for and a little dose pragmatic advice.

    I'm not, by any means, a "pixel peeper" but I do like to feel comfortable and secure with my gear before gambling on a client's project. Luckily, in my market, the clients mostly care about the end result and how the footage turns out so it allows me a certain amount of freedom to use tools like the Ursa Mini 4.6k Pro - as long as it produces "the goods".

    I'll probably shoot a couple of the "tests" above and definitely some skin-tones because that was my main reason for trying the camera in the first place. My FS7, while a very good camera that I intend to keep using, can be a bit challenging with those.
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