{"course":{"slug":"image-editing","title":"Editing an Image","url":"https://addaly.com/learn/image-editing","level":"beginner","track":"create"},"lesson":{"slug":"why-composites-fail","title":"Six mismatches, and the eye finds them all","url":"https://addaly.com/learn/image-editing/why-composites-fail","position":50,"of":78,"minutes":8,"answer":"Composites fail on six measurable mismatches (perspective, scale, light direction, light quality, edge softness and grain) and the fastest ways to find them are flipping the image, shrinking it and blurring it.","keyIdea":"Composites fail on six measurable mismatches (perspective, scale, light direction, light quality, edge softness and grain) and the fastest ways to find them are flipping the image, shrinking it and blurring it, because each reveals a different class of error."},"body":{"format":"markdown","text":"## Wrong before it is noticed\n\nShow somebody a bad composite and they will say it looks fake before they can say why. That is not vagueness; it is how visual processing works. Consistency of light, perspective and focus is computed early and automatically, long before anything reaches conscious attention, and an inconsistency registers as wrongness with no accompanying explanation.\n\nThis is useful, because it means the fix is never \"make it look better\". It is a checklist of six specific things, each of which can be measured and corrected.\n\n## The six\n\n**1. Perspective.** Was the camera at the same height and the same distance relative to the subject in both photographs? A product shot from slightly above, dropped onto a table shot from eye level, sits wrong no matter how good the cut-out is. This is geometry and it is the next lesson.\n\n**2. Scale.** Is the element the right size relative to everything else on its ground plane? Scale errors are surprisingly hard to see directly and obvious via shadows and contact points.\n\n**3. Light direction.** Which way do the shadows fall on the element, and which way do they fall in the plate? A subject lit from the left placed in a scene lit from the right is the commonest failure and the easiest to check: look at the noses, the shadows under objects, and the shaded side of anything round.\n\n**4. Light quality and colour.** Hard or soft, warm or cool. A subject shot with a small flash has hard-edged shadows with sharp boundaries; an overcast street has shadows so soft they are barely shadows. Mixing them fails even when the direction agrees.\n\n**5. Edge quality.** Does the element's outline have the same softness as everything else at that distance? A razor-sharp cut-out in a photograph shot at f/2 announces itself immediately, and so does a soft element in a deep-focus scene.\n\n**6. Grain, noise and texture.** A clean studio element in a grainy night scene reads as pasted, because the surface texture of the two images differs. So does a JPEG-compressed element in a clean raw plate.\n\nThere is a seventh that is not about the element at all: **occlusion and contact**. Does the object touch anything? Does anything pass in front of it? An element floating with nothing overlapping it looks pasted even when the six are right, because real objects in a scene are partly hidden by other objects.\n\n## The order to work in\n\nDo them in the order that avoids redoing work.\n\n> Figure: The order that avoids doing the work twice. Steps: 1. Geometry first (Perspective, scale, position. Everything else depends on where the thing is, and the horizon crossing a standing figure fixes the scale exactly.); 2. Colour and exposure, roughly (Enough that you are judging the rest against something plausible rather than against an obviously wrong element.); 3. Light direction and quality (Relight with gradients clipped to the element, and cool the shade as well as darkening it. A hard-lit element cannot be relit from the opposite side; those shadows are baked in.); 4. Shadow and contact (The tight dark contact shadow first. Without it an element has no position at all, and a cast shadow alone still floats.); 5. Edge softness, then grain (Match the depth of field at that distance, then add grain to the whole flattened composite. Grain on the element alone leaves two textures in one picture.). Almost none of the time goes on the cut-out, which is the part beginners expect to be hard. A simple element into a simple plate is an hour; a person into a complex scene with matched light is half a day, and nearly all of it is steps three to five.\n\n1. **Geometry first**: perspective, scale, position. Everything else depends on where the thing is.\n2. **Colour and exposure**, roughly, so you are judging the rest against something plausible.\n3. **Light direction and quality**, by relighting the element.\n4. **Shadow and contact**, which fixes both the floating problem and most remaining scale ambiguity.\n5. **Edge quality**, matched to the depth of field.\n6. **Grain and noise**, last, applied over the whole composite rather than to the element.\n\nThat last point matters: adding grain to the element alone leaves two grain patterns. Adding it to a flattened copy of the whole composite unifies them.\n\n## Choosing the plate first\n\nThe single largest determinant of whether a composite will work is whether the two photographs were compatible to begin with.\n\nWhen you can choose, choose:\n\n- **Overcast or open shade** for both, because soft light has no hard shadows to match.\n- **Similar focal length**, because that sets the perspective relationship.\n- **Similar camera height.**\n- **Neutral light colour** in both, which you can then grade together.\n\nWhen you cannot choose (a client supplies two photographs) the honest assessment comes first. A subject shot with direct sun from the right cannot go into a scene with direct sun from the left. Reversing the element horizontally sometimes solves it, and then any text or asymmetric detail on the subject is mirrored. Say what is achievable before the work starts.\n\n## The checking method\n\nWhen the composite is done, three checks:\n\n**Flip it horizontally.** Your eye has habituated to the image. Mirrored, it is unfamiliar again and the errors reappear. Flip back afterwards.\n\n**Look at a small version.** Shrink it to 300 pixels. Errors of tone, contrast and light direction survive; errors of edge detail disappear. If it reads as wrong at 300 pixels, the problem is structural rather than in the mask.\n\n**Blur it heavily.** A 20-pixel Gaussian on a flattened copy leaves only the broad tonal and colour structure. If the element still stands out as a differently-toned lump, the exposure or colour match is wrong regardless of how good the edges are.\n\nAll three take seconds, and all three find different classes of error.\n\n## The honest note on effort\n\nA convincing composite is slow. A simple element into a simple plate is an hour; a person into a complex scene with matched light is half a day. Nearly all of that time is items 3 to 6 on the list, not the cut-out, which is the part beginners expect to be hard.\n\nIf the schedule does not allow it, the better decision is usually a composite that is *visibly* a composite: a cut-out on a flat or graphic background, which is honest design rather than a failed illusion. The failure mode to avoid is the half-finished attempt at realism, which reads as incompetence where a graphic treatment would have read as a choice."},"check":{"question":"An editor finishes a composite and it still looks wrong. They flatten a copy, apply a 20-pixel Gaussian blur, and the pasted element is still visible as a distinct lump. What does this tell them?","options":[{"text":"The mask has a hard edge, which survives heavy blurring as a visible boundary.","correct":false,"tempting":"Expects edge detail to survive a blur that is specifically chosen to destroy it: a 20-pixel blur removes any edge signature, which is why the test isolates broad tone."},{"text":"The problem is in the element's overall exposure or colour rather than in its edges, because the blur has removed all edge information and the mismatch remains.","correct":true},{"text":"The grain of the element does not match the plate, which the blur has averaged into a visible density difference.","correct":false,"tempting":"Identifies a real mismatch whose effect a blur removes rather than reveals, since averaging grain produces the same mean value in both regions."},{"text":"The element is at the wrong scale, and blurring makes scale errors more obvious by removing distracting detail.","correct":false,"tempting":"Names an error the test does not isolate: scale is judged from relationships to other objects, which the blur obscures rather than clarifies."}]},"prev":{"slug":"what-cannot-be-repaired","title":"Four losses that no tool undoes","url":"https://addaly.com/learn/image-editing/what-cannot-be-repaired"},"next":{"slug":"perspective-scale-and-horizon","title":"The horizon tells you where the camera stood","url":"https://addaly.com/learn/image-editing/perspective-scale-and-horizon"},"authorship":"Founder and series editor: Dr Mustafa Mun. Written by AI models to a written standard. Exam keys checked blind by a second model: 3,665 of 3,666 agreed. Academic review invited.","review":{"status":"Draft, open for academic review"},"cite":"Addaly (2026) 'Six mismatches, and the eye finds them all', in Editing an Image. Edited by M. Mun. Addaly. Available at: https://addaly.com/learn/image-editing/why-composites-fail (Accessed: 13 October 2026).","licence":{"name":"CC BY-NC-SA 4.0","url":"https://creativecommons.org/licenses/by-nc-sa/4.0/"},"reader":{"schema":1,"title":"Six mismatches, and the eye finds them all","courseTitle":"Editing an Image","module":{"index":6,"slug":"compositing","title":"Compositing: making two pictures one"},"answer":null,"keyIdea":"Composites fail on six measurable mismatches (perspective, scale, light direction, light quality, edge softness and grain) and the fastest ways to find them are flipping the image, shrinking it and blurring it, because each reveals a different class of error.","hero":{"kind":"figure","figure":{"t":"figure","label":"Figure 6.1","figure":{"type":"flow","steps":[{"label":"Geometry first","detail":"Perspective, scale, position. Everything else depends on where the thing is, and the horizon crossing a standing figure fixes the scale exactly."},{"label":"Colour and exposure, roughly","detail":"Enough that you are judging the rest against something plausible rather than against an obviously wrong element."},{"label":"Light direction and quality","detail":"Relight with gradients clipped to the element, and cool the shade as well as darkening it. A hard-lit element cannot be relit from the opposite side; those shadows are baked in."},{"label":"Shadow and contact","detail":"The tight dark contact shadow first. Without it an element has no position at all, and a cast shadow alone still floats."},{"label":"Edge softness, then grain","detail":"Match the depth of field at that distance, then add grain to the whole flattened composite. Grain on the element alone leaves two textures in one picture."}],"title":"The order that avoids doing the work twice","caption":"Almost none of the time goes on the cut-out, which is the part beginners expect to be hard. A simple element into a simple plate is an hour; a person into a complex scene with matched light is half a day, and nearly all of it is steps three to five."},"alt":"Figure: The order that avoids doing the work twice. Steps: 1. Geometry first (Perspective, scale, position. Everything else depends on where the thing is, and the horizon crossing a standing figure fixes the scale exactly.); 2. Colour and exposure, roughly (Enough that you are judging the rest against something plausible rather than against an obviously wrong element.); 3. Light direction and quality (Relight with gradients clipped to the element, and cool the shade as well as darkening it. A hard-lit element cannot be relit from the opposite side; those shadows are baked in.); 4. Shadow and contact (The tight dark contact shadow first. Without it an element has no position at all, and a cast shadow alone still floats.); 5. Edge softness, then grain (Match the depth of field at that distance, then add grain to the whole flattened composite. Grain on the element alone leaves two textures in one picture.). Almost none of the time goes on the cut-out, which is the part beginners expect to be hard. A simple element into a simple plate is an hour; a person into a complex scene with matched light is half a day, and nearly all of it is steps three to five."}},"blocks":[{"t":"h2","id":"wrong-before-it-is-noticed","runs":[{"text":"Wrong before it is noticed"}]},{"t":"p","runs":[{"text":"Show somebody a bad composite and they will say it looks fake before they can say why. That is not vagueness; it is how visual processing works. Consistency of light, perspective and focus is computed early and automatically, long before anything reaches conscious attention, and an inconsistency registers as wrongness with no accompanying explanation."}]},{"t":"p","runs":[{"text":"This is useful, because it means the fix is never “make it look better”. It is a checklist of six specific things, each of which can be measured and corrected."}]},{"t":"h2","id":"the-six","runs":[{"text":"The six"}]},{"t":"p","runs":[{"text":"1. Perspective.","b":true},{"text":" Was the camera at the same height and the same distance relative to the subject in both photographs? A product shot from slightly above, dropped onto a table shot from eye level, sits wrong no matter how good the cut-out is. This is geometry and it is the next lesson."}]},{"t":"p","runs":[{"text":"2. Scale.","b":true},{"text":" Is the element the right size relative to everything else on its ground plane? Scale errors are surprisingly hard to see directly and obvious via shadows and contact points."}]},{"t":"p","runs":[{"text":"3. Light direction.","b":true},{"text":" Which way do the shadows fall on the element, and which way do they fall in the plate? A subject lit from the left placed in a scene lit from the right is the commonest failure and the easiest to check: look at the noses, the shadows under objects, and the shaded side of anything round."}]},{"t":"p","runs":[{"text":"4. Light quality and colour.","b":true},{"text":" Hard or soft, warm or cool. A subject shot with a small flash has hard-edged shadows with sharp boundaries; an overcast street has shadows so soft they are barely shadows. Mixing them fails even when the direction agrees."}]},{"t":"p","runs":[{"text":"5. Edge quality.","b":true},{"text":" Does the element’s outline have the same softness as everything else at that distance? A razor-sharp cut-out in a photograph shot at f/2 announces itself immediately, and so does a soft element in a deep-focus scene."}]},{"t":"p","runs":[{"text":"6. Grain, noise and texture.","b":true},{"text":" A clean studio element in a grainy night scene reads as pasted, because the surface texture of the two images differs. So does a JPEG-compressed element in a clean raw plate."}]},{"t":"p","runs":[{"text":"There is a seventh that is not about the element at all: "},{"text":"occlusion and contact","b":true},{"text":". Does the object touch anything? Does anything pass in front of it? An element floating with nothing overlapping it looks pasted even when the six are right, because real objects in a scene are partly hidden by other objects."}]},{"t":"h2","id":"the-order-to-work-in","runs":[{"text":"The order to work in"}]},{"t":"p","runs":[{"text":"Do them in the order that avoids redoing work."}]},{"t":"ol","start":1,"items":[[{"text":"Geometry first","b":true},{"text":": perspective, scale, position. Everything else depends on where the thing is."}],[{"text":"Colour and exposure","b":true},{"text":", roughly, so you are judging the rest against something plausible."}],[{"text":"Light direction and quality","b":true},{"text":", by relighting the element."}],[{"text":"Shadow and contact","b":true},{"text":", which fixes both the floating problem and most remaining scale ambiguity."}],[{"text":"Edge quality","b":true},{"text":", matched to the depth of field."}],[{"text":"Grain and noise","b":true},{"text":", last, applied over the whole composite rather than to the element."}]]},{"t":"p","runs":[{"text":"That last point matters: adding grain to the element alone leaves two grain patterns. Adding it to a flattened copy of the whole composite unifies them."}]},{"t":"h2","id":"choosing-the-plate-first","runs":[{"text":"Choosing the plate first"}]},{"t":"p","runs":[{"text":"The single largest determinant of whether a composite will work is whether the two photographs were compatible to begin with."}]},{"t":"p","runs":[{"text":"When you can choose, choose:"}]},{"t":"ul","items":[[{"text":"Overcast or open shade","b":true},{"text":" for both, because soft light has no hard shadows to match."}],[{"text":"Similar focal length","b":true},{"text":", because that sets the perspective relationship."}],[{"text":"Similar camera height.","b":true}],[{"text":"Neutral light colour","b":true},{"text":" in both, which you can then grade together."}]]},{"t":"p","runs":[{"text":"When you cannot choose (a client supplies two photographs) the honest assessment comes first. A subject shot with direct sun from the right cannot go into a scene with direct sun from the left. Reversing the element horizontally sometimes solves it, and then any text or asymmetric detail on the subject is mirrored. Say what is achievable before the work starts."}]},{"t":"h2","id":"the-checking-method","runs":[{"text":"The checking method"}]},{"t":"p","runs":[{"text":"When the composite is done, three checks:"}]},{"t":"p","runs":[{"text":"Flip it horizontally.","b":true},{"text":" Your eye has habituated to the image. Mirrored, it is unfamiliar again and the errors reappear. Flip back afterwards."}]},{"t":"p","runs":[{"text":"Look at a small version.","b":true},{"text":" Shrink it to 300 pixels. Errors of tone, contrast and light direction survive; errors of edge detail disappear. If it reads as wrong at 300 pixels, the problem is structural rather than in the mask."}]},{"t":"p","runs":[{"text":"Blur it heavily.","b":true},{"text":" A 20-pixel Gaussian on a flattened copy leaves only the broad tonal and colour structure. If the element still stands out as a differently-toned lump, the exposure or colour match is wrong regardless of how good the edges are."}]},{"t":"p","runs":[{"text":"All three take seconds, and all three find different classes of error."}]},{"t":"h2","id":"the-honest-note-on-effort","runs":[{"text":"The honest note on effort"}]},{"t":"p","runs":[{"text":"A convincing composite is slow. A simple element into a simple plate is an hour; a person into a complex scene with matched light is half a day. Nearly all of that time is items 3 to 6 on the list, not the cut-out, which is the part beginners expect to be hard."}]},{"t":"p","runs":[{"text":"If the schedule does not allow it, the better decision is usually a composite that is "},{"text":"visibly","i":true},{"text":" a composite: a cut-out on a flat or graphic background, which is honest design rather than a failed illusion. The failure mode to avoid is the half-finished attempt at realism, which reads as incompetence where a graphic treatment would have read as a choice."}]}],"check":{"question":[{"text":"An editor finishes a composite and it still looks wrong. They flatten a copy, apply a 20-pixel Gaussian blur, and the pasted element is still visible as a distinct lump. What does this tell them?"}],"options":[{"text":[{"text":"The mask has a hard edge, which survives heavy blurring as a visible boundary."}],"correct":false,"tempting":[{"text":"Expects edge detail to survive a blur that is specifically chosen to destroy it: a 20-pixel blur removes any edge signature, which is why the test isolates broad tone."}]},{"text":[{"text":"The problem is in the element’s overall exposure or colour rather than in its edges, because the blur has removed all edge information and the mismatch remains."}],"correct":true,"tempting":null},{"text":[{"text":"The grain of the element does not match the plate, which the blur has averaged into a visible density difference."}],"correct":false,"tempting":[{"text":"Identifies a real mismatch whose effect a blur removes rather than reveals, since averaging grain produces the same mean value in both regions."}]},{"text":[{"text":"The element is at the wrong scale, and blurring makes scale errors more obvious by removing distracting detail."}],"correct":false,"tempting":[{"text":"Names an error the test does not isolate: scale is judged from relationships to other objects, which the blur obscures rather than clarifies."}]}],"order":[2,3,1,0],"why":null},"prev":{"slug":"what-cannot-be-repaired","title":"Four losses that no tool undoes","minutes":9},"next":{"slug":"perspective-scale-and-horizon","title":"The horizon tells you where the camera stood","minutes":9}}}