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Fixed Pattern Noise / Spec?


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#1 Carl King

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Posted 01 July 2014 - 03:14 PM

Hi,

 

I've tested a Blackmagic Design 4K camera and was very disappointed by the vertical fixed noise pattern. It was apparent to me even before I knew it was called that, or that there was an online petition about it. I could even see it on the internal LCD while shooting, and immediately thought "This is not something I want to work with."

 

I have seen some well-respected video geeks defending Blackmagic by saying, "There is nothing wrong with the camera -- it is just the spec." 

 

In all sincerity, what is meant by that argument? 

 

I don't understand why raising the ISO / ASA one stop from Native 400 to 800 and getting that much noise is considered acceptable. I am used to working with 5Dmk3 or C100, and having much more room to work the ISO / ASA before getting that much noise. Having only one choice above 400 (and introducing that much noise) seems odd. 

 

Would some of the more experienced cinematographers mind explaining? Is this something more common in what is considered a "cinema" workflow? Meaning, are "cinema" cameras generally set at their Native ISO / ASA -- leaving control of exposure through aperture, shutter, and lighting?

 

-Carl. 


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#2 Carl King

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Posted 01 July 2014 - 03:23 PM

PS -- my primary line of work is music documentaries and educational content, so I have very little experience with a narrative filmmaking workflow. 

 

-Carl. 


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#3 Adrian Sierkowski

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Posted 01 July 2014 - 03:23 PM

Lower end cameras, by providence of their insane compressions, have lots of time to hide that at the expense of dynamic range and the like. The nearly unadulterated signal off of a BM camera also means all the flaws which would be hidden in, say, h.264 compression or any GoP based compression, show through.

That said, what you are seeing in the BM4K is really a limitation of the specific sensor they have gone with. Other sensors, and better put, much more expensive and often proprietary sensors, often include hardware and software designs which minimize such things.

As for the one stop push, you are effectively doubling the "signal" in the camera by pushing it one stop, and therefore doubling any of the issues therein. The sensor, and really every sensor, has a "native" sweet spot, the native ASA, wherein you maximize dynamic range and minimize noise and the like. In the case of the 4K that's about 400iso, or so they say I haven't tested. On something like an Epic, it's 800 ASA, same for Alexa and the Pocket/Cinema. On cameras such as the Alexa, Epic, for example, though, there is much more "stuff" between the sensor and the recorder which helps with noise thresholds and color reproduction etc.


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