GH4 Nailing Exposure Quickly on the GH4

Daniel Brown said:
I did a video today using the 70% values on the subject's skin tones.

Main Sequence.Still005.jpg
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Though the graded shot indeed has skin tones at about 70%, the original, ungraded shot you posted has those skin tones at just above 60%. At least that's how they read on my waveform monitor in Premiere.
 
Bern Caughey said:
It's not the grade but how the camera is setup.

I suspect you've pushed the Master Pedestal &/or Highlight/Shadow too far. What are your settings?

I've made similar mistakes on other 8bit cameras & it's easy to spot the problem on a gradient like your background.
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Master Pedestal was at +15. I was testing Andrew Reid's recommended settings. I didn't think of this being an issue, since everything else I've shot so far has graded spectacularly.

Here's where I'm at:

CinelikeD

Contrast: -2
Sharpness: -5
Saturation: -5
Hue: +0

i.Dynamic: Off
i.Resolution: Standard

Master Ped.: +15
Highlight / Shadow: None (No Change)

Should I scratch this profile completely? Dial down certain things?
 
Daniel Brown said:
Master Pedestal was at +15. ....

Should I scratch this profile completely? Dial down certain things?
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There are still various opinions about Master Pedestal, but my tests and my logic tell me that setting it to +15 is counterproductive. It doesn't increase dynamic range. In fact, it decreases it by lifting the lowest black of your image to a higher level and thus reduces the number of values that an 8-bit codec can use to represent the image. So instead of having 256 possible values for a pixel's brightness, it reduces it to something like 217 values.

I have read bad things about iResolution on photography forums. Apparently, it's just a localized edge enhancement function that adds false detail and when set too high can give the image a strange "painterly" look.

If I were you, I'd set Master Ped to 0, especially in a controlled lighting situation like the one you posted. I'd experiment with different levels of saturation, too. Cinelike-D already has less saturated skin tones than other GH4 profiles when set to 0. Setting saturation to -5 might be too much, unless you are going for that look on purpose.
 
After testing I've decided to leave the Master Pedastal & Highlight/Shadow at 0. This may change when I start recording 10bit.

In a similar lighting scenario my setup is:

Picture Profile: CineLike D
Contrast: -5
Sharpness: -5
NR: -5
Saturation: -2
Hue: 0
Highlight/Shadow: 0/0
i.Dynamic: Off
i.Resolution: Off
Master Pedestal: 0
Luminance Level: 0-255
 
stoneinapond said:
To me that looks like a light shadow from the subject.
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This.

It looks like a cast shadow from the subject onto the background. The "banding" is probably the umbra and penumbra of the cast shadow.

If it were an actual banded transition between bit-depth levels, the trasition would appear sharper, and we wouldn't see all that gradation within the area in question -- there would just be more bands instead of gradation.

It appears that the OP was using a large, softer and cooler source (possibly daylight balanced), and there was warmer ambient light (possibly tungsten balanced) filling the cast shadow.
 
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And here I have tweaked the background with the Red channel so you can see what is really happening back there.
 

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h-munster said:
It appears that the OP was using a large, softer and cooler source (possibly daylight balanced), and there was warmer ambient light (possibly tungsten balanced) filling the cast shadow.
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David W. Jones said:
And here I have tweaked the background with the Red channel so you can see what is really happening back there.
Click to expand...

My boss and I were talking about this over lunch. We thought it may just be due to the lighting and non-ideal shooting location. It wasn't a studio setting and we didn't flag off the natural light leaking into the scene. Plus in general 8-bit 4:2:0 doesn't do well with uniform, neutral backgrounds.

The softbox and fill light were tungsten while natural daylight was lightly leaking into the scene from too many windows to flag off. The windows were however not nearly as bright as they appear in the image here.

Here's where we shot for context:

notideal.jpg
 
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David W. Jones said:
Here is a quick grade. I see nasty artifacts & banding.
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Thanks for the tweaked images.

I don't see banding, but I do see artifacts.

The artifacts are also visible in the original image.

Judging from OP's side-view diagram (an overhead chart might have been clearer), there's a lot going on lighting-wise:
- window light;
- tungsten production lights;
- overhead linear fluorescents;
- overhead recessed can fixtures (possibly with 2800K tungsten or CFL with some version of tungsten/daylight/cool-white);
- bounce board possibly reflecting some mixture of the sources;
- posts casting shadows in half of the frame (from the window light);
- etc.
 
I thought I would write a quick conclusion about the original topic of 'Nailing Exposure Quickly on the GH4' for the sake of Google searchers and DVXUser forum browsers. The topic got a bit derailed, focusing on some issues with a video I shot. Anyways...

There are four methods for exposing an image during a run and gun situation on the GH4.

1) Zebras
2) Scene exposure tool
3) Histogram
4) Eyes

Zebras are perfect for exposing people's skin or for making sure you don't blow out precious highlights in a scene. 65-70% for skin and 85-90% for general. This can really let you select what you're exposing for. Zebras are really useful for telling when you're going to lose detail due to overexposure of backgrounds or foregrounds.

The scene exposure tool is very useful when trying to expose a wide shot (in averaging mode) or specific spot (in spot mode). This can be set up in metering settings. Perfect for landscapes and general everyday shooting. However, if in averaging mode, this is not ideal for low light because it can cause an image to be overexposed in important areas like a lamp or computer screen.

The Histogram is useful, but not ideal for run and gun situations. You can use it to tell if your scene is too crushed in the dark areas or clipping in the highlights.

Don't forget your eyes. They are indispensable, especially for low light. In low lighting you should expose for how the eye sees it. Take a step back, look at your scene, and ask yourself "Does it really look like it was shot in a dark setting, or have I exposed it to look like it's fully lit?".

I personally like zebras. They serve most of my purposes, and I find that it's simple enough to switch between 70% and 90% when mapped to a Function button.

Any edits, criticism, or input welcome. :)
 
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