Every composite I’ve ever seen fall apart does so for the same reason. Not because the mask was sloppy. Not because the resolution didn’t match. It’s because the light in the subject came from a completely different universe than the light in the background plate.

I learned this the hard way. Early in my agency days, I spent the better part of a week on a composite for a client pitch — a person standing in a dramatic desert landscape at golden hour. The cutout was clean. The colors were close. But something was off, and I couldn’t name it until a senior designer leaned over my shoulder and said, “Your shadows are going the wrong direction.” She was right. The background light source was hitting from camera left at roughly 45 degrees, and my subject’s shadows were pointing straight down like it was noon. The composite looked like a hostage photo taken in a studio and dropped onto a postcard.

That one correction — rotating and rematching the light logic — changed everything. It’s the foundation of believable compositing, and it’s where I want to start.

Reading the Light Before You Touch a Single Layer

Before you open the Extract panel or reach for a layer mask, spend two minutes analyzing your background plate. Look for three things: the direction of the key light, the color temperature of that light, and the intensity of the shadows.

Direction is easiest to find by looking at where highlights fall on objects in the scene. Color temperature shows up in the shadow areas more than the highlights — an overcast sky will push cool blue-gray into shadows, while a golden hour scene punches warm amber into them. Shadow intensity tells you how hard or soft the light source is. A harsh midday sun gives you tight, dark shadows with sharp edges. An overcast sky gives you soft, diffuse shadows with almost no edge at all.

Write these three things down, literally, before you start placing your subject. I keep a sticky note on monitor two (yes, I have three) with these values noted so I don’t drift as I work.

Matching Color Temperature With Curves, Not Hue/Saturation

Most people reach for Hue/Saturation when they need to shift the color of a composited subject. Don’t. Hue/Saturation changes color uniformly across the tonal range, which looks synthetic. Real-world lighting shifts color differently in the highlights than in the shadows.

Instead, use a Curves adjustment layer clipped to your subject layer. To warm a subject to match a golden hour background, pull the Red channel curve up slightly in the midtones (move the midpoint from input 128 to roughly output 138), push the Blue channel down slightly in the midtones (128 down to about 118), and leave the Green channel mostly alone or nudge it up by 3 to 5 points in the highlights.

These are small moves. The numbers feel tiny but the visual difference is significant. Compositing is almost always about restraint — you’re trying to make the viewer not notice anything, not make them go “wow, look at that color.”

Building Edge Lighting That Sells the Illusion

Even with perfect color temperature matching, flat-lit subjects look pasted onto backgrounds. You need to simulate the way environmental light wraps around the edges of a subject. This is called rim or edge lighting, and faking it convincingly is one of the most satisfying skills in compositing.

Create a new empty layer clipped to your subject. Set the blend mode to Screen for light effects or Soft Light for a more integrated glow. Sample a color from the brightest part of your background light source, then use a large, soft brush (300 to 600 pixels, hardness at 0%, opacity around 15 to 20%) and paint along the edge of the subject that faces the key light direction. Build it up in 3 to 4 passes rather than one heavy stroke.

For the opposite edge, do the same thing on a new layer set to Multiply, but sample from the shadow areas of your background. This adds fill shadow wrap and makes the subject feel like it exists inside the environment rather than floating in front of it.

Unifying the Scene With a Color Grade Layer

Once your subject is matched and your edge lighting is done, everything still needs to be glued together. I always add a single color grade at the top of the layer stack that applies to the entire composite, not just the subject.

My go-to is a Gradient Map set to Soft Light at 10 to 15% opacity. I set the shadow color to a desaturated version of the scene’s dominant shadow hue (for a golden hour desert scene, something like a warm dark brown, hex around #2C1A0E), and the highlight color to a near-white with just a hint of the key light color (hex around #FFF5E0 for that same scene). This single layer ties the subject and background together visually by imposing a shared tonal signature across both.

After that, I add a Camera Raw Filter on a merged stamp layer (Ctrl+Alt+Shift+E) and make micro adjustments — usually just dropping clarity by 5 to 8 points and adding 3 to 5 points of vignette. This softens any remaining hard edges between elements and grounds everything in the same optical context.

The One Thing Most Tutorials Skip

I once had a student ask me why their composite still looked off after they had done everything right. I looked at their file and the technical execution was genuinely solid. The problem was the ground contact. Their subject had no shadow on the surface they were standing on. No contact shadow means no gravity. No gravity means your brain registers something is wrong even if it can’t say why.

Always add a contact shadow. New layer, Multiply blend mode, a soft black brush at 5 to 8% opacity, a few strokes directly under the subject where they meet the surface. That’s it. It takes thirty seconds and it’s the difference between a subject standing in a scene and a subject floating over it.

Light logic is the grammar of compositing. Get it wrong and nothing else you do will save the image. Get it right and even an imperfect mask will hold up.