'Honest' compression artifacts. There are various approaches to how to do lossy compression. Different techniques lead to different artifacts. Some artifacts are less "annoying" than other artifacts. For example, blurring, smearing and mild ringing are probably not very annoying (or even desireable to some, because it might eliminate noise and increase perceived sharpness), while pixelation, blockiness and color banding are annoying and obvious compression artifacts. Also, some artifacts are not very "honest", in the sense that the image looks deceptively better than it actually is. For example, JBIG2 in lossy mode or HEIC at low bitrates can produce images that look like they are high-quality (e.g. they have sharp details at the pixel level), but they are actually very different from the uncompressed image. For example, JPEG artifacts are "honest" and "annoying", while WebP and HEIC artifacts are "not honest" and "not annoying". FUIF aims for compression artifacts that are "honest" and "not annoying". At low bitrates, pixelation will become obvious at a 1:1 scale, but the overall image fidelity will still be as high as possible (e.g. comparing a downscaled lossy FUIF image to a downscaled original). Rationale: this is a matter of preference, but we think that image fidelity is more important than hiding the fact that lossy compression was used. An image format should not act as an artistic filter that modifies an image more than necessary. At least that's our opinion.