Focusing speed in the dark with the 1Dx and Focus Assist. Some lenses suck.

JimKarczewski

Are there different types of USM motors in the lenses? I ask because last night I decided to go play natural light shooter where it was necessary to crank up ISO 24k to get a decent shutter speed at say f2 on 2 of the lenses I was trying (the 50/1.4 and the 85/1.8) Both of those lenses with the assistance of a focusing beam from a 580EXII set to not fire (except of course use the AF assist beam.)

Camera was set to single shot (otherwise the AF assist of the 580EX would had been useless..) and those 2 mentioned lenses just were DOGS. Complete DOGS. If I popped on any of my L glass (16-35, 24-70, 70-200) almost instant focusing.

So I'm guessing there is something different in the focusing system between L and Non-L glass??? Disappointed I couldn't at least use my 50/1.4 for shots (at about f2) and honestly having never been able to shoot in such low light before (while the 5DII has ISO 24K it's not something I'd ever use vs the 1Dx)

Matthew Saville

Yes, there is a difference in USM, google "ring type USM vs rod type USM" or something like that.

However, both the 50 1.4 and the 85 1.8 have the newer type of USM, as far as I know. Maybe I'm wrong about the 50 1.4, but I know I'm not wrong about the 85 1.8... Only the super-cheap lenses like the 50 1.8 have truly abysmal AF motors...

I would love to hear more about what you mean by "dogs". Did they not acquire focus well? Were they just slow, but still focusing accurately? Front-focus or back-focus maybe? Or were they just completely hit-and-miss?

=Matt=

JimKarczewski

Matthew Saville wrote: »

I would love to hear more about what you mean by "dogs". Did they not acquire focus well? Were they just slow, but still focusing accurately? Front-focus or back-focus maybe? Or were they just completely hit-and-miss?

=Matt=

Matt-

By "Dogs" I mean, they would take anywhere from 1-4 seconds to lock focus, if they even locked focus. Stupid me should had done manual focus, it would had been faster and probably more accurate. If I put my L lenses on the focus lock was almost immediate.

Matthew Saville

JimKarczewski wrote: »

Matt-

By "Dogs" I mean, they would take anywhere from 1-4 seconds to lock focus, if they even locked focus. Stupid me should had done manual focus, it would had been faster and probably more accurate. If I put my L lenses on the focus lock was almost immediate.

That doesn't sound right. Since your signature tells me you have experience with other camera bodies, don't those bodies focus well with your 50 and 85? It defies logic to think that the 1DX should be somehow crippled to only work well with high-end lenses. If anything, EVERY lens you put on a flagship body, even the cheapest, should work a little better than on a lesser body. I'm sure you would agree!

Clean the lens contacts, check the focus calibration using a tripod, cable release, and immobile high-contrast subject, ...and if all else fails, send things in for calibration / service.

I'm sure others will have a few other suggestions as to why these lenses might be focusing worse on the 1DX.

=Matt=

ziggy53

Canon has the following AF motor technologies:

Micro-Motor
Micro-Motor USM
Micro-Motor USM II
Ring USM
Stepper-Motor

The simple micro-motor is used in the basic and entry level consumer lenses, and has the advantages of being light and cheap to produce. It has relatively little torque but can run at a fairly high speed. Unfortunately, lenses with this technology generally have poorer focus accuracy than any of the USM technologies. Micro-motor driven lenses have an audible "hum" in operation, due to the motor type and gearing involved.

The Micro-Motor USM and Micro-Motor USM II are similar in size to the micro-motor, but they use the principle of piezo vibrations to drive the motor segments at a very high frequency, improving focus accuracy and with little noise. Since they use gear trains there can be some sound from the gears, and the AF speed is generally not up to sports standards. (The total driven weight of the lens elements being focused along with the gear ratios helps to determine AF speed.) The difference in these 2 types of motor relates to their size, but performance is similar

Ring USM is a more "direct drive" approach to AF motor technology and presents the current best in AF speed and accuracy. Canon's best sports lenses tend to use ring-USM AF motor technology. Since there is no gearing involved, ring-USM lenses move very quietly and the motor is intrinsically self-braking.

Stepper-Motor drive is the latest AF motor technology and only available in the "STM" series lenses. While these are the newest lenses in the Canon lineup, so they are not known very well, they are noted for being quiet and fast. Because stepper motors can know focus positions through counting the finite steps and rotations, both focus direction and focus distance information should be available to the host body. I am not aware of any current Canon body using this direction and/or distance information, but benefits for both still image and (especially) video applications may soon be able to leverage the information to improve focus accuracy and focus repeatability. (Programmed follow-focus and repeatable focus pulls are predictable future capabilities.)


The following is a list of current USM motor, lens applications (courtesy Canon-Europe):

Ring-type USM
EF 14mm f/2.8L II USM
EF 20mm f/2.8 USM
EF 24mm f/1.4L II USM
EF 28mm f/1.8 USM
EF 35mm f/1.4L USM
EF 50mm f/1.4L USM
EF 85mm f/1.8 USM
EF 85mm f/1.2L II USM
EF 100mm f/2 USM
EF 100mm f/2.8 Macro USM
EF 135mm f/2L USM
EF 180mm f/3.5L Macro USM
EF 200mm f/2L IS USM
EF 200mm f/2.8L USM
EF 300mm f/2.8L IS USM
EF 300mm f/4L IS USM
EF 400mm f/2.8L IS USM
EF 400mm f/4 DO IS USM
EF 400mm f/5.6L USM
EF 500mm f/4L IS USM
EF 600mm f/4L IS USM
EF 800mm f/5.6L IS USM
EF-S 60mm f/2.8 Macro USM
EF 16-35mm f/2.8L II USM
EF 16-35mm f/2.8L II USM
EF 17-40mm f/4L USM
EF 20-35mm f/3.5-4.5 USM
EF 24-70mm f/2.8L USM
EF 24-85mm f/4-5.6 USM
EF 24-105mm f/4L IS USM
EF 28-105mm f/3.5-4.5 II USM
EF 28-135mm f/3.5-5.6 IS USM
EF 28-300mm f/3.5-5.6L IS USM
EF 70-200mm f/2.8L USM
EF 70-200mm f/2.8L IS USM
EF 70-200mm f/4L USM
EF 70-200mm f/4L IS USM
EF 70-300mm f/4.5-5.6 DO IS USM
EF 100-300mm f/4.5-5.6 USM
EF 100-400mm f/4.5-5.6L IS USM
EF-S 10-22mm f/3.5-4.5 USM
EF-S 17-55mm f/2.8 IS USM
EF-S 17-85mm f/4-5.6 IS USM

Micro USM
EF 50mm f/1.4 USM
EF 28-200mm f/3.5-5.6 USM
EF 55-200 f/4.5-5.6 II USM
EF 70-300mm f/4-5.6 IS USM
EF 75-300mm f/4.5-5.6 III USM

Micro USM II
EF 28-105mm f/4-5.6 USM
EF-S 18-55mm f/3.5-5.6 II USM

ziggy53

I'm afraid that I would have to see the scene being photographed before I would comment on what particularly might have happened in this instance.

I do know from my own experience that reflections from mirror or glass surfaces, as well as specular lights in the background, will potentially throw off "any" current passive AF system. There are probably other circumstances I'm forgetting too.

JimKarczewski

Ziggy, I'll get some pics as soon as I get them processed...