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Message: <blockquote data-quote="Blue439" data-source="post: 826824" data-attributes="member: 53455">I would say that every lens has a sweet spot, an f-stop value (or a series of such values) at which it performs best optically. This best optical performance chiefly concerns sharpness, color aberrations and resistance to flare, but it may also has an influence on color rendition. Of course, this is a question of lens type by lens type, not in general. For example, this particular lens will have a sweet spot at ƒ/5.6 to 8, and that will be true for all copies of that same lens, but not true for another type of lens.What is also for sure is that such best performance will not be at the very small values mentioned by the original poster years ago: values such as ƒ/14 or 22 are not going to bring out the best in a lens, as diffraction would have set in to degrade optical performance.I also beg to differ with Mogiskito above: when they say “The more light being let in, the deeper and richer the color”, one may be lead to believe (as I am) that colors will be best rendered when the lens is wide open. This is almost never true, the maximum aperture is not where a lens performs best, color-wise or otherwise, and very far from that. Only very expensive modern lenses achieve that, one good recent example is Nikon’s 135mm ƒ/1.8 S Plena which has surprised all reviewers with its image quality wide open. Other lenses need to be stopped down to their specific sweet spot, as I explain above. Sweet spots can very often be found by looking up “MTF charts” on the internet for a specific lens type.</blockquote>

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