The three most misunderstood GH4 settings – PART 3: Highlight & Shadow
Not all curve controls are created equal. I thought I knew what to expect from the GH4 Highlight and Shadow settings. I was wrong.
In part 1 I demonstrated how the “Luminance Level” setting was not a tool for protecting highlights. In part 2 I demonstrated how the “Master Pedestal” setting simply shifts the black level without revealing any more real detail. Now, I’ll end this three parter with other setting that “flat” shooters love to crank-up…
Highlight and Shadow
First, let’s talk about what this setting is not…it’s not a gamma curve. Nope. Really. I promise. Look at the on-screen curve as you adjust highlight and shadow. What stays in place? That’s right, the midpoint. You can’t adjust the midpoint. You can’t directly adjust the gamma. (For the record, a traditional gamma curve would directly adjust nothing but the midpoint.)
So, what do these settings do?* Or what should they do? Let’s start with my expectation.
As a curve adjustment, and based on the graphics the camera displays during adjustment, I expected the settings to leave the absolute black point (0%), midpoint (50%) and white point (100%) the same. In between those points, I expected that the Shadow setting would shift more of the data towards (+ settings) or away (- settings) from the midpoint. Conversely, I expected that the Highlight setting would shift more of the data towards (- settings) or away (- settings) from the midpoint. Additionally, I expected that the total amount of highlight or shadow data would remain the same…just distributed differently relative to the midpoint.
Is that what they do…well, sort of. Let’s go to the tape:
So what’s happening here?
What I expected to see, and did:
- The 50% midpoint basically stays put.
- The 100% white point basically stays put.
What I didn’t expect to see, but did:
- The absolute black point is shifted upwards (losing usable data) as the Shadow setting is increased.**
- While white point stays consistent, the total quantity of highlight data lowers (not just shifts) as the Highlight setting is lowered.
* They really are two separate settings, grouped together – they don’t really impact each other. It is convenient to manipulate them as one, though.
** I think this was partly exacerbated by the fact that my image was over exposed, and those didn’t have any true blacks. Even so, looking at the +4 image seems to indicate that the black point is shifting. I need to shoot another test with a properly exposed image to confirm.