Curves vs. Sliders: Two Ways to Recover an Underexposed RAW Photo

I was shooting macro when I spotted a spider on a leaf high up in a tree — not easy to reach. I took several shots to nail the focus, but the flash couldn't keep up — it happens.

Later you decide whether the image is worth saving. This one was. The composition wasn't bad, the focus was sharp, and the detail was hiding in the RAW data. It was worth trying to pull it back.

I tried to recover it two ways. Once using only adjustment sliders, and once using only curves. Same image, same goal — two different paths. The idea was simple: to see what curves can actually do on their own, because most people skip them entirely.

The Unprocessed RAW

Here's the RAW image with no adjustments. This is what the sensor captured — dark, flat, and not much to look at. But that's the thing about RAW files: what you see at first glance is not what's actually there.

Pushing this much shadow data will inevitably bring up sensor noise along with the detail — that's the trade-off with any severely underexposed photo — but let's focus on the tonal recovery itself.

First Attempt: Sliders

The obvious move. I opened the Adjustments panel in Pixigy on my iPhone and started working through the sliders:

• Exposure raised to recover brightness
• Shadows lifted aggressively to pull detail from the darks
• Contrast pushed hard to restore depth lost from heavy shadow lifting
• Highlights and Whites pulled back to control brighter textures
• Blacks dropped to anchor the tonal floor
• Vibrance up, Saturation back — bringing color back naturally without overdoing it

Within seconds, the image came back. Detail and texture recovered, the edit done. Sliders work exactly this way — they're fast, they're direct, each one locks onto a specific tonal range and you see it move in real time. For a straight recovery like this, they do exactly what you need.

Second Attempt: Curves Only

I reset everything back to zero and opened the curves tool. This time, no sliders at all — the entire edit done with just the luminance curve and the RGB (master) curve.

On the luminance curve, I dragged the whites point down into the lower third of the tonal range. Shadow detail came forward, but what made the difference was how it came forward — the shape of the curve defined how gradually shadows transitioned into midtones. It wasn't a blanket lift. It was a reshape of the tonal response itself.

With the RGB curve, I pushed the overall brightness a bit further, added some saturation, and lifted the deepest blacks to keep the feel open rather than crushed.

The image was there — but it arrived differently. The tonal transitions were smoother. The midtones had more dimension. The shadow recovery had a quality to it that felt less mechanical. The histogram spread evenly, and the edit held up well at full zoom. And the whole thing was three points on two curves. That's it.

What I Noticed

Both edits recovered the image. Both produced something I could work with. But they got there differently, and the difference was visible.

Sliders are direct — each one targets a defined tonal range, and adjusting them is immediate and predictable. The curves tool does something else: instead of choosing how much to adjust a range, you define the shape of the adjustment itself. Dragging a point on the luminance curve doesn't just brighten shadows — it defines the rate at which shadow tones transition into midtones, and how midtones roll into highlights.

The luminance curve turned out to be the key. It adjusts brightness without affecting color, keeping color relationships intact while reshaping the light. This matters especially in RAW photo editing, where preserving the full tonal and color information your sensor captured is the whole point.

And the thing that surprised me most, even though it shouldn't have: how simple the actual edit was. Curves may look intimidating — the grid, the diagonal line, the multiple channels. But the entire edit here was a single drag on the luminance curve and two points on the RGB curve. No complex shapes, no dozen control points. If you've avoided curves in mobile photo editing because they seemed like a desktop-only tool, this is a good example of how little it actually takes to get meaningful results.

Better Together

After doing this comparison, the takeaway wasn't that one tool is better than the other. It's that they do different things well.

Sliders are fast for establishing a baseline — getting the overall exposure and contrast into the right range. Curves are where you refine — shaping tonal transitions, fine-tuning shadow recovery, and adjusting brightness in specific ranges without side effects. In practice, the best version of this image would probably start with a rough slider pass and finish with curves to shape the tonal character. They complement each other, and using both gives you the full range of control.

Try It Yourself

Open a severely underexposed RAW file in Pixigy on your iPhone or iPad. Edit it once using sliders, reset, then edit it again using only the luminance and RGB curves. Compare the two results side by side — not to pick a winner, but to feel the difference in how each tool handles the recovery.

The curves tool is available in the editing view, with luminance, RGB, red, green, and blue channels. If you've been avoiding curves because they seemed complex — start with an underexposed image and a single point.

The Pixigy Team