Image stabilization and focus speed

ziggy53

Has anyone noticed a correlation between Image Stabilization (IS) and the speed at which a camera locks focus?

I followed a pro around this weekend who was using a Canon 1D MkII and a Canon 28-135IS lens. He was achieving very fast focus latch and it got me wondering if there was a relationship between the two technologies.

My own thought is that the focus algorithm has an easier time with an image which doesn't "jump around", thus potentially faster focussing.

Ideas? Speculation? Ruminations? (I "Googled" but didn't come up with anything.)

Thanks,

ziggy53

luckyrwe

My 400/5.6 seems to AF lock the fastest of my three lenses, the 24-70 being very close then finally the 70-200IS. I think the 70-200 may be slower due to IS, but it also has more glass to haul around.

wxwax

ziggy, yer profile says yer shooting with a KM A2. Is that a Konica Minolta DiMage A2?

If so, it's not surprising that a pro body and a not-too-slow lens will autofocus faster. Also, doesn't the A2 have image stabilization?

If that's not what KM A2 means, please ignore.

Chase

I used a 70-200 f2.8 IS on my dreb and that thing focused really, really quickly. It handily destroyed any other lens i have tested on it.

ziggy53

wxwax wrote:

ziggy, yer profile says yer shooting with a KM A2. Is that a Konica Minolta DiMage A2?

If so, it's not surprising that a pro body and a not-too-slow lens will autofocus faster. Also, doesn't the A2 have image stabilization?

If that's not what KM A2 means, please ignore.

wxwax,

I am getting a Canon 350XT, possibly this week. Since IS lenses are more expensive than non-IS glass, part of the cost justification could be if they also focus faster. I will gradually acquire some new EOS-mount lenses, so I'd like as many perceptions/opinions as possible before-hand.

At work I also use a Kodak DCS460 (ancient dSLR, 6MP, Nikon based) and I think my perception of lens focus speed is mostly based on that experience. All I have for that camera are two prime Nikon lenses, and they're not too slow, but the Canon 28-135 was much faster.

(I've also played with a Canon dRebel 300 with the 18-55 kit lens and a Nikon D70 with the Nikon 18-70 kit lens recently, and I think the Canon 28-135 would beat even the Nikon in Hotel lighting. I haven't done any real tests, so these are simply my observational perceptions.)

My KonicaMinolta A2 is a prosumer digicam with builtin IS and yes, it really does work and it does help eliminate camera shake. I also use a Sony F828 at work and I actually take the Minolta in to work every day because it saves me time on some shots and makes my life easier when hand-held will suffice. The Sony is much tougher to hold at full telephoto, even though it has a lens 1 stop faster. Neither the KM A2 or the Sony F828 is going to set any focus speed records, compared to a dSLR with decent lenses. The F828 has the holographic focus mode which is simply amazing in extremely low-light for focus accuracy.

Thanks,

ziggy53

wxwax

Cool beans, zippy. FWIW, I've never heard of IS helping autofocus. Obviously, what really helps is a faster lens, and also the smaller the elements the faster it should be.

mercphoto

wxwax wrote:

Cool beans, zippy. FWIW, I've never heard of IS helping autofocus. Obviously, what really helps is a faster lens, and also the smaller the elements the faster it should be.

I am suspicious that IS helps AF as well. The image doesn't stabilize immediately, which discounts the "stabler image focuses faster" theory. Also, the 28-135 is not known as a particularly fast focusing lens.

Even the faster lens focusing faster theory is not always true, but it seems to be usually true. I think that fast glass focuses faster than slow glass (even though fast glass has heavier elements). And I think primes focus faster than zooms. As a general rule of thumb.

deckeda

ziggy53 wrote:

Has anyone noticed a correlation between Image Stabilization (IS) and the speed at which a camera locks focus?

No. For example, my 75-300 IS often has to hunt for focus ... but since long lenses have shallow depth of field, that might not be surprising.

Auto focus speed is a function of several things, such as:
1) Is the focus mechanism sophisticated? Canon's USM lenses, particularly the ring-type, tend to focus very quickly.

2) Is it a fast lens? Since modern lenses only close down to the exposure aperture when the shot is taken, a fast lens not only makes for a brighter viewfinder for you, but lets in more light for the camera's auto-focus system.