CRT filters for iPhone and iPad emulators

Choose the display, then the strength

Nearest-pixel mode leaves the original pixel edges sharp and unblended. CRT treatments bring scanlines, masks and edge shading; LCD treatments layer in a pixel or subpixel grid. Either way you are changing how the picture is drawn, not the game's resolution.

• Look at the unfiltered picture first, as a baseline.
• Inspect small text, bright edges and shadow detail rather than only the title screen.
• Judge the result at the size and orientation you really play in.

No integer-scale requirement

Integer scaling gives every game pixel a whole number of display pixels. That stays crisp, yet it often wastes a strip of screen. Retropa's advanced filters instead measure the real output area, so their structure is not locked to 2x, 3x or any other whole multiple. You keep the game's aspect ratio and still fill the viewport your phone or skin provides.

• The output size decides the pattern, not a fixed multiplier.
• Aspect ratio is preserved even when the viewport is not a whole multiple.
• Compare presets at your normal playing size before settling on one.

More than a scanline overlay

CRT Lite, LCD Grid and Scanline are the light presets, and they are honest about it. Advanced presets model parts of the display itself: how wide the beam looks, how light passes through phosphor, or how a liquid-crystal cell reflects light. A source-sized grid can look uneven when the picture is scaled between whole pixels; using the real output area lets fine detail settle more naturally. None of this means every ordinary filter demands integer scaling, or that some device and preset combination will never show an artifact.

What the browser comparison shows

On the website you can preview the basic filters alongside CRT V4, Trinitron V1 and DMG, which follow their native formulas. The advanced modes are adapted from those formulas, pixel-footprint integration included, and share one presentation curve. The browser build skips temporal persistence, the full multi-pass bloom chain and native color management. Treat it as a demonstration of display character, not a pixel-for-pixel match to Metal output or a capture of real gameplay.

Import RetroArch shader presets

One .slangp preset may point at several shader passes, textures and parameter values. Bring those dependencies along in the same import. A preset on its own can be incomplete, and a .slang file describes a single shader rather than a whole collection.

• Stick to packages built for the supported shader workflow.
• When a preset will not load, look at its referenced files and compatibility before you touch the game.
• Drop to a lighter preset if a long chain hurts frame pacing or drains the battery.

Picture quality has a performance cost

A multi-pass filter asks more of the GPU than a plain nearest-pixel picture does. How much depends on the device, the emulator core, the output resolution and the preset itself. Retropa makes no promise that an imported shader will run the same way on every iPhone. Advanced filters need Retropa Plus; the app shows you which presets qualify.