Encontré la explicación, aquí os la dejo:
Blu Ray Screencaps – The Dark Knight » DarkRealmFox | DarkRealmFoxThe Dark Knight's 35mm shot footage was scanned from an InterPositive at 4K in order to make the IMAX prints, the DMR processing ( digital media remastering ) upconverted the 35mm footage, grain reduction and sharpening was applied, then it was recorded back out to an IMAX negative for creation of the IMAX prints and it is very likely this print was used for the Blu Ray edition. The problem is ugly edge enhancement. Check out frames 8 and 15 for examples and check out frame 12 which is a 70mm IMAX shot scene.
Its a very good film but it's let down by the poor transfer, you could argue it represents exactly what people saw in IMAX cinemas but sharpening is so ugly on blu ray.