Using a lens without a hood or filter, is likely to degrade the quality of your images - both of these improve contrast, but also impact in other ways too, such as removing or reducing flare, increases colour saturation and therefore accuracy. I would not mind betting that with an AF lens, focussing speed and accuracy, is also affected, since any diffusion or defraction reduces it's ability to 'snap' into focus on something. Not often mentioned are the problems that flare causes when editing an image, as it 'creeps' across the boundaries or and edges of an object or colour, a bit like fringing. This can cause major problems because when trying to locate the edge of an object from that surrounding it. I suspect that the loss of definition that the lack of either of these causes, is a bit like having ultra-accurate hearing or less than perfect eyesight. Unless someone better equipped than you points out what is missing or shouldn't be there. This is a bit off tangent but I remember meeting someone who mixes paints for Film and TV scenery and was amazed by their ability to see minute differences and identify what was needed to enable a more accurate match.