If your phone offers RAW, use RAW. It generally preserves the most original sensor data and includes the metadata the camera records, making it the best option for technical analysis like MTF.

JPEG also supports extensive EXIF metadata, but it is lossy and already includes in-camera processing such as tone, sharpening, noise reduction, and color conversion. That processing can affect measurements.

PNG is not a good choice here: it typically carries less camera metadata and isn’t a common camera-native capture format.

WebP also isn’t ideal for MTF work. Its advantages don’t help for this use, and it’s typically 8-bit output with image processing already applied.

TIFF can support rich metadata and even lossless or uncompressed storage, but camera-recorded TIFF is usually still a processed image rather than untouched sensor data, so it’s generally not better than RAW for measurement purposes.

If RAW is unavailable, use JPEG with the least aggressive processing settings your phone allows.