Red-eye happens when light from a flash reflects off the retina at the back of the subject’s eye and travels back through the pupil to the camera. The pupil is dilated in low light, so a lot of light enters, hits the blood-rich retina, and comes back to your lens, giving that characteristic red glow from the blood vessels. This is different from lens flare, which is stray light scattering inside the camera lens; sensor bloom, which is saturation causing bright pixels to smear; and chromatic aberration, which is color fringing around edges due to how a lens bends different colors. To reduce red-eye, use red-eye reduction features, increase ambient lighting so pupils contract, or move/bounce the flash or use off-camera lighting.

Creating a selection with straight-line segments is done with the polygonal Lasso Tool. You place points around the edge of what you want to select, and each click creates a straight line to the next point. When you connect back to the start, the area inside becomes the selection. This is ideal when you need precise, angular edges or geometric shapes. The magic wand selects pixels based on color similarity, the quick selection tool grows a selection by following edges as you brush, and the regular Lasso Tool draws freehand with curved edges. So the polygonal Lasso Tool is the one that builds a selection from straight lines.

Leading lines pull the viewer’s eye along a path through the image. In this photo, the railroad tracks are the strongest lines, starting in the foreground and receding into the distance. As perspective makes parallel lines appear to converge toward the horizon, your eye naturally follows the rails, creating depth and a sense of movement. This directional emphasis is what makes it a clear example of leading lines. Other techniques describe different effects but don’t capture what’s happening here. The scene isn’t about placing a subject on grid lines (rule of thirds), surrounding a subject with elements (framing), or creating mirrored balance (symmetry); it’s about how the lines themselves guide your gaze through the frame. The vanishing point where the tracks seem to meet the horizon is a natural outcome of perspective, reinforcing the leading lines effect.

Layers let you edit non-destructively. Each element can sit on its own layer, so you can adjust, reposition, or hide parts of the image without changing the rest. You can apply effects or styles to a specific layer, like shadows or color tweaks, giving precise control over how that element looks. Changing the stacking order lets you move content forward or backward in the picture plane, altering which elements sit on top of others. This makes the editing process dynamic, because you can experiment with different arrangements and styles without starting from scratch. Keep in mind that layers don’t reduce file size, and they don’t prevent edits; and they don’t automatically flatten when you save—layers stay separate until you choose to merge or export a flattened file.