AF-I vs AF-S

[gen.PIRX]

takie male mam pytanko co mnie nurtuje: czym rozni sie AF-I od AF-S w teorii i praktyce - i jak sie ma to do D70 - chodzi mi np o tele 300 z AF-I - czy jest to duzo szybsze od AF i czy duzo wolniejsze od AF-S :D ...itd

[gALL]

AF-I to protoplasta AF-S.

Wiecej za www.kenrockwell.com

"AF-I

These add an internal motor to focus the lens. There is no mechanical AF connection between camera and lens, it's done electronically.

Nikon introduced these in their super-telephotos in the early 1990s, which is the only sort of lenses you'll find as AF-I.

All Canon AF lenses have been this way, even the cheap ones, all along.

Not all Nikon AF cameras can autofocus with these lenses, make sure to investigate if you are buying an AF-I lens. AF-I lenses are usually $10,000 super-teles, so Nikon rightfully didn't go to the expense of adding this ability to the low-end cameras that would not be likely to be used with these lenses. In other words, why add $10 to the cost of every N60 when none of them would likely to be used on a 600mm f/4?

AF-I introduced a sloppy A/M, or automatic switching between AF and manual focus operation. It's a kludge; you have to keep your finger on the AF button (usually the shutter on the camera) while you grab the focus ring and it does eventually klunk over to manual focus. Nice try, but still years behind Canon's system introduced years ago. Nikon's AF-S lenses are much better this way.

The 300/2.8 and 600/4 AF-I lenses are not very fast. They sort of grind while focusing. The 400/2.8 AF-I is newer and much better. The 400/2.8 AF-I motor is super fast and very quiet, with just a hint of a very high-pitched whine that sounds like an AF-S lens. The 400/2.8 AF-I is as fast as the AF-S version, but the A/M switching is still primitive.

AF-I lenses usually offer several very nice focus hold buttons on the lens itself. The AF-I lenses are built like the tanks you should expect, unlike the plasticy AF-S lenses.

All AF-I lenses are AF and AI-s, and probably AF-D. They work great on manual focus cameras, too, giving you all features. You may need to have a coupling prong installed for pre-AI cameras.

I have measured that AF-I lenses draw the same amount of battery power from an F100 as do ordinary AF lenses.

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AF-S

These lenses have magical motors built into them to focus. The main advantage is not speed, but that you can just grab the focus ring and turn it even in the AF mode to get instant manual focusing, without having to mess with any switches.

The AF-S motor is driven by the electronics of your camera, and therefore you still get faster focusing with the faster cameras like the F5 and D1H and slower focusing with the slower cameras like N65 and D100. Only the newer cameras have the required electronics, so not all AF cameras can use AF-S lenses.

AF-S first came out only on Nikon's $1,500 lenses, and today AF-S can be found on $300 lenses. AF-S is always better than regular focus, mostly again due to the easy manual focusing and not necessarily speed.

All AF-S lenses are AF-D, and if you've been paying attention, they are also usually AI-s for complete compatibility with manual focus cameras. In this case, the S in AF-S has nothing to do with the s in AI-s. They fit all Nikon SLR cameras, and give all features with all manual focus cameras. You may need to have a coupling prong installed for metering on pre-AI cameras. Watch it, AF-S G series lenses are not AI-s and will not work on manual cameras.

I have measured the power drain from the F100 camera to focus these lenses. They take the same power that conventional Nikon AF lenses do."

[Pawel Pawlak]

AFi ma już wewnętrzny motor i jest sporo szybsz od AF. Co do różnic szybkości mięcy AFI / AFS to trzeba by porównywać konkretne modele. Z tego co pamiętam, AFI300 ma chyba jako jedne z pierwszych blokadę ostrości, tak samo jak AFS ma 3 strefy AF.Poza tym AFI wspołpracują z tymi samymi konwerterami co AFS. Mój znajomy, który miał jedną i drugą 300tkę, twierzi że różnica w szybkości nie jest wielka.