PXW-X70: Legend of the Green Shadow!

[Paul Anderegg]

No, not a comic book hero, rather a consistent inconsistency that may exist in HD mode on the X70.

My X70 has a definitive GREEN push in shadows, those would be the dark areas above 0IRE. When I took the camera into a broadcast shop, the guy said he could not calibrate it, because he could not find a black balance adjustment. In the past, I would simply add a +1 magenta in the WB PP LL menu. The problem with that is AWB, or any WB setting would have a magenta cast on highlights, like whites.

Now this issue is obviously more pronounced and noticeable at night, at higher gains. Adding black gamma + adjustments just makes it more apparent. The solution, as I have come to terms with, is to fix it in post. In FCPX, going to the color board, selecting shadows, moving it over to where global is, and going -1 (green), eliminates this for the most part, without affecting highlights.

For some reason, the only way to get an accurate black balance on my camera is to be in AWB mode. In a different post, someone commented they have the same green shadows I do, so i thought i would post this fix, because post is the ONLY method of turning green shadows into black ones even with the best PP color correction settings on my X70.

Paul

[Joachim Claus]

Paul,

this is a typical effect for low light bahavior. If you consider the sensitivity spec of sensors (CMOS as well as CCD), you will find, that green has highest sensitivity. In dark environments, red and blue loose their output signals earlier than green. The result is, that you get green shadows in darkness. This can only be corrected in the camera, if there are still red signals and blue signals present and can be boosted by color adjustments. However, if blue and red do not provide sufficient signals, there is no way to boost. I hope this helps to understand the green shadow effect.

Joachim

[Paul Anderegg]

Unfortunately, in the X70, this cannot be adjusted in camera. :-(

Strange fact though, in 4K UHD mode, you DO NOT get the green shadow effect. You do however got pretty blue spreckles, which look similar to those you see in Cinematone mode on the CX900/AX100.

Paul

[Ignacio Rodriguez]

I have been able to get gracefully around the green shadows problem by using Catalyst Browse (free Sony software) to bring up mid tones and leave the shadows alone. The Catalyst Browse curve works far better than what I was doing previously: bringing the mid tones up and the shadows down using color correction in Apple Compressor ended up adding unacceptable noise and I could never seem to get it right.

I am sure there is still some green noise in there but it is practically invisible. Further tweaking the curve could probably get rid of the green in more challenging shots with lower light and/or less contrast.

[Paul Anderegg]

I tried adjusting things in CB previously, but the waveforms 100IRE display limit kept that from going anywhere.

If you shoot a greyscale chart with the X70 properly white balanced, then crop the black bars to full screen on the vectorscope, you will see the little center blob firmly over on the green vector side of things, while white remains centered.

This really is an issue that should be considered a MANDATORY post process, because that little bit of green can and will adversely throw off all your colors, even midtones to some degree. Play with shadow colors in your NLE and watch what even slight magenta/green changes do to the overall look of your coloromitry. On my X180, it has a black balance issue as well, but it allowed R and B black adjustments, so that you can push those to the center on the vectorscope for prettier colors. The auto black push to black balance menu option in the X180 doesn't work correctly. :)

Paul

[Tom Grushka]

Frustrating. Any way we could get a petition from X70 users going to Sony to get these color (and maybe highlight) issues fixed with a firmware update?

Then again, could this be considered a warranty issue? If I send in my X70 to fix this issue, and Sony does not fix it, is it a lemon?

[Paul Anderegg]

The black balance is an "issue", The highlight thing is a limitation of the technology. I think at a minimum, Sony should give us a black balance adjustment, ABB or R B off-setting like in the X180. I have come to live with the fact that to get pretty video at night from the X70, you must grade and correct it in post. A 100% white clip option would be useful as well.

Paul

[Tom Grushka]

What do you mean by "limitation of the technology"? Does it have to do with only one sensor instead of three (other one sensor cameras I've used don't seem to have the highlight problem as much)? Is it "clipping" signals at 100IRE instead of 107/109 like other cameras? Limited dynamic range of this sensor? Something else? I've never seen highlights blown quite like the X70/AX100 before. Are you sure a software fix is impossible? I'm talking about something like lamps with shades, etc. totally blowing out very quickly instead of gracefully like other cameras, if that makes sense. Changing the knee setting does seem to help a little.

[Paul Anderegg]

By technology I mean the cost of the components and processors they have put in the X70 to save money. My consumer police scanners are technology limited in their ability to receive compared to a Motorola with much more advanced components. The same is true for trying to make the most of a single sensor.

Sony could probably put a multi-matrix control in the camera in place of the "color correction" setup. That would at least allow proper color balancing, but the highlight issue is probably beyond firmware.

Paul

[Tom Grushka]

It's just weird, because I had a Canon XF 100 before and that didn't have the highlight issue (or seem to) and cost about the same. I also have a Sony a6000, which is APS-C. I'll have to check, but don't think harsh highlights are a problem on that one. Then there's other consumer cams on the market that certainly have other shortcomings, such as low rate codecs. Its just bizarre. But if I could change only one thing on the X70, it would be the color. It would at least be calibratable to better spec than what you discovered, and surely that could be firmware fixed, I think.

[Paul Anderegg]

Yeah, colors that are off are my number one pet peeve about video cameras. When you shoot at night (ENG) and you have lots of bright intense colors popping, it is really noticeable and distracting to have very acute color shifts on PRIMARY colors! :(

Paul

[Paul Anderegg]

This is my 2014 X70...my 2017 X70 has the issue, but not as severe.

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