Lens focusing speed

Duckys54

I'm currently looking at getting the Canon EF 85mm ƒ1.8 and I was wondering how fast it would focus in low light accurately on my 40D versus something like the 50mm ƒ1.4 or another similarly priced lens.

Also, what would you say is the fastest focusing lens Canon makes or does the camera body have more to do with it?

Thanks,
Trevor

ziggy53

Duckys54 wrote:

I'm currently looking at getting the Canon EF 85mm ƒ1.8 and I was wondering how fast it would focus in low light accurately on my 40D versus something like the 50mm ƒ1.4 or another similarly priced lens.

Also, what would you say is the fastest focusing lens Canon makes or does the camera body have more to do with it?

Thanks,
Trevor

The Canon EF 85mm, f1.8 USM uses a "genuine" ring-type (arc-drive) motor which is both fast and accurate. It is commonly used as a sports lens as a testament to its speed.

The fastest AF lenses are the Canon "L" lenses which are also designed for sports. The fastest that I own are the EF 70-200mm, f2.8L USM and the EF 135mm, f2L USM.

The camera body does contribute to AF speed and accuracy and the Canon 1D and 1Ds series bodies have the fastest AF section in the Canon lineup. Sensitivity in low light is part of the reason and those bodies' AF sensors are twice as sensitive in low-light as the subordinate bodies.

There is also a difference due to the processor and it has been noted that the 5D MKII is about the same as the original 5D is single-shot AF mode, but seems noticeably/considerably faster in AI-Servo mode.

The Canon 1D MKIV is reported to have a further improved AF for low-light and may (or may not) prove to be the fastest AF yet. It will take some time and testing to tell for sure.

I can say for sure that the 1D MKII is faster than the 40D in AF speed and accuracy, especially in low-light, from my own experience. The 70-200mm and 135mm mentioned before are just superb on the 1D MKII body.

divamum

The 85/1.8 and 100/f2 are both champs in low light conditions, as is the 135L. I use them with an xsi, and even with the "lesser" AF of that camera, they are extremely fast most of the time!