You have seen this even if you did not know its name. A character's head sits in front of the clock on someone's lock screen, as though the numbers were printed on a wall behind them, and it looks designed rather than downloaded.
Then you try it with your own anime art and the toggle is greyed out, or it switches itself off when you move the image. Nothing in the interface explains why.
The rule behind it is simpler than it looks. Once you know what iOS checks for, you can tell from a thumbnail whether a picture will work.
What the depth effect actually does
When you set a lock screen photo, iOS looks for a main subject and separates it from the background. If it finds one, it can draw that subject on top of the clock instead of behind it. That is the layered look.
This is the same subject detection that lets you press and hold a photo to lift a person out of it. It is not depth data from a portrait-mode shot, which is why it works on drawings at all.
The switch lives in the lock screen editor, under the customise or more-options menu, once a photo is chosen. On some models and older iOS versions it is not offered at all, so if you never see it, that may be your device rather than your image.
iOS is looking for a subject, not a portrait
The system wants one clear thing it can cut out. Anime art is often ideal, because cel shading gives hard outlines and flat colour areas, far easier to separate than a soft photographic edge.
Specifically, it wants a subject that is large in the frame, clearly separated from what sits behind it, and roughly upright. A chest-up or head-and-shoulders crop is close to perfect. A full-body figure in a landscape is much weaker: small subject, more competing detail.
Why some anime art never triggers it
If a picture refuses to work, it is usually one of these five.
The character is surrounded by effects. Energy auras, flames, smoke, petals and glow blur the boundary between subject and background, and the prettier the effect, the less clean the edge.
Colours run together. Dark hair against a dark background, or white clothing against a pale sky, leaves little for the system to work with.
There is more than one subject. Two characters, or a large weapon crossing the frame, leaves no obvious single thing to lift.
The art is a collage. Panel layouts, framed borders, text overlays and montage edits get treated as one flat image.
The file is low quality. Compression softens exactly the edges subject detection depends on, so a blurry upscale often fails where a sharp original works first try.
The clock is half of the equation
This is the part that is easy to miss. The effect only appears when the subject actually overlaps the clock, so if the character's head sits well below the time, there is nothing to layer and iOS will not offer it.
There is a limit the other way too. If the subject would cover so much of the time that you could not read it, the system switches the effect off rather than hide your clock. Aim for a narrow band: the top of the head crossing into the bottom of the digits without swallowing them.
Pinch and drag instead of hunting for another image
Most images that fail are the right picture at the wrong zoom. In the lock screen editor you can pinch to zoom and drag to reposition before saving. Zoom in slightly, pull the image down so the head just reaches the bottom of the clock, and watch the numbers as you move. When the digits drop behind the head, you have it. It is worth trying before you go looking for a different image.
Widgets and filters quietly switch it off
Two settings disable the effect without explaining themselves.
Widgets under the clock are the common one. When that row is populated, the layered look is generally turned off, since the subject would cover the widgets. Remove them and the option often reappears.
Wallpaper styles are the other. Swiping between the colour treatments in the editor — black and white, duotone, colour washes — can disable depth on some of them, so if the toggle vanishes after you change an image's look, swipe back to the plain style. Behaviour on both points has shifted between iOS versions, so test rather than assume.
Picking art that works on the first try
Look for a chest-up or waist-up character filling half the frame, against a background clearly different in tone from their hair and clothes. Simple backgrounds beat detailed ones, sharp outlines beat soft painted styles, one character beats two.
Portrait-shaped images win for a practical reason: a wide image gets cropped to your screen, and that crop usually pushes the head out of the band where it needs to be. A collection like Anime Wallpaper 4K – Live is easier to work with here because the art is already cut to phone proportions.
Quick answers
Why is the depth effect greyed out on my lock screen?
The usual causes are a subject that does not overlap the clock, widgets under the clock, a non-plain wallpaper style, or an image with no clear single subject. Remove the widgets first, then switch to the plain style, then zoom so the head reaches the digits.
Does the depth effect work on every iPhone?
No. It arrived with the redesigned lock screen and is not available on every model or iOS version, so older phones may not offer it at all. If you are on a current version and still never see the option, check your model before troubleshooting images.
Can I use the depth effect with a live wallpaper?
Generally not on the same lock screen. The layered look and Live Photo playback tend to be alternatives rather than a pair, and how that is handled has varied across iOS releases. If you want both, save a depth-effect still as one lock screen and a live one as another, since iOS lets you keep several.
Does it work on the home screen too?
No. It is a lock screen effect, built around layering the subject with the clock. A home screen wallpaper sits flat behind the icons regardless, which is why a calmer crop or a blurred version usually works better there.
Where to get it
Depth works best with sharp, phone-shaped art of a single character, which is a narrow thing to search for. Anime Wallpaper 4K – Live has a large set of vertical character crops at full phone resolution, which is most of the work.
Save two or three candidates, then spend five minutes with the pinch-and-drag trick rather than settling for the first one that works.