My experince might be a bit critical as I am using rather slim DoF lenses like EF100 f2 and EF85 f1.2 L II for the tests. Please stated your equipments when sharing your experinces. Subject & lighting details also please provide if possible la

And here is my findings on 300D -> Sucks no matter what.

10D/30D -> about 8~9/10 are sharp with EF100 f2. While 85L wide open drop to 1/3 (30D) ~ 1/5(10D) of the shots only. Subject static, some slight turning around body la...

40D -> Increase the success rate into about 5~6 out of 10 shots with 85L wide open. Subject static.

5D -> 10/10 sharp on EF50 f1.4 wide open, 8/10 on 85L wide open. Subject static.

1D mark III -> 0 out of 10 sharp on 85L wide open. Must be something wrong with the setting.

1Ds mark III -> 7 out of 10 sharp on 85L wide open

While with 70-200 f2.8 USM L, those 10D/30D/40D perform flawlessly of close to 9/10 shots sharp. Even on moving subject such as runway, can easily get 7 out of 10 sharp. I guess the major contribution on the excellent result is because of the ultra-fast and smooth autofocusing.

So if you ask me to rank my 40D for its autofocusing performance, I can only give 5~6 out of 10. And it seems 5D autofocusing sensors are superior than my 40D. And lenses does make differences. I found those lenses that fast in autofocus tends to do better job. Maybe same thing can be applied on Nikon gears.

Hope you guys can be honest on the test results. I am also interested to know those popular camera like 350D/400D as well as Nikon D300 performance.

Best Lenses on Autofocusing (close to perfect success rate) -> EF85 f1.8 USM, EF100 f2 USM, EF135 f2 USM L, EF70-200 f2.8 USM L

Lenses with normal success rate -> EFS17-55 f2.8 USM IS, EF17-40 f4, EF16-35 f2.8, EF50 f1.4, EF50 f1.2 USM L

The worst autofocus performer -> EF85 f1.2 L -> Thus it is the best lense to test camera body autofocus capability.

there are 2 types of USM ... the ring type (which is the best, and Canon most probably put it on higher end lenses) and micro drive motor type (which is low end, cheapo, and prone to breakdown).

lao this statement will cause problem woh later...

Ya I know... but I prefer to know the actual performance in real life rather than on paper. Even the 85L is on ring type USM, but it is the slowest autofocusing lense in Canon lineup.


What's the problem?

It is sharing of personal experince. Nothing more than that.

And to be frank, it is also the only reason I might want to upgrade my camera body is to improve the success rate with 85L.

Anyway, I believe this discussion might not concern most of the forumers here as they do not need critical autofocusing with slim DoF...

I guess it also depends on the metering capability of the camera.

metering? You mean exposure?

Actually exposure issue can be solve via raw file captured...

Handshake pula can be solve by using high shutter speed...

It is the success rate of autofocusing with small DoF lenses that is the headache... If OOF, it cannot be fixed!

Also depends on the subject matter right? Darker conditions harder for camera to selectively focus.

Some lenses have their sharpest focus points at the center rather than at the side. Quite obvious for some of the third party lenses.

Right also...

I found my 40D really hunt on very low light condition. Example; back to Vietnam trip that I need ISO1600 on f1.2 that only give me 1/30. I guess it is out of my camera limitation. And I think the autofocusing limit is around ISO1600 / f1.2 / 1/125, which still can give me some sharp pictures.

Talking about only center sharp, I found my friend Nikon 85 f1.4 only sharp (wide open) around the center, even it is on the cropped sensor of D200/D300. Do you have the same findings? Even my friend 50 f1.2 L also suffer the same (wide open).

Yeah, I tried the 85mm f/1.4 at wide open on a D200. Center is extremely sharp but side focusing still looks a little soft. Need to turn on in camera sharpening to max and get slightly better results.

i'm not refering to exposure, but the light metering capability.

So my finding is still valid.

On the other hand, I found the Canon 85 f1.2 L II is sharp across the screen for crop sensor such as 40D. But yet to try on Full Frame at the border yet... However, I believe the Canon cost about double of the Nikon... And very slow in autofocusing....

Like one Sifu used to say, if a lense is too expensive and not affordable for him/her to buy & use, it is a bad lense. Thus all super telephoto lenses like 300 f2.8 and above are bad lenses to me...

Sometime it is so hard to find affordable solutions...

(1) 85L perform great on 5D, but I do not like the effective focal length.

(2) 1D series should be good with 85L, but no money...

So the best at this moment is using 40D + 85L, shoot more with re-focus every picture in order to get more picture sharp in focus lo....

The brighter the lens, the more precision is required by the lens motor.

That's why F1.2 lenses are slower to focus.

Can't you save your focus bias to the 85mm F1.2L lens you have? I thought the 40D would remember any AF finetuning.

I think only 1D has that feature...

But anyway, it will not help because I am not facing front/back focus.

I will seriously try on some 1D mark III with experinced users and with the right setting in the future... If it can get me at least 7 out of 10 sharps pictures at f1.2, I might consider upgrade.

Its a portrait lens. Its meant to be like that.