Focus lock issue with Canon EOS 400D Digital

09 Oct

Posted by Jayce as Hardware, Photography

After getting my Canon EOS 400D Digital back from service, I took a lot of shots with it. There is no back focus issue. However, I still face fail to focus lock issue as I mention at Check Canon EOS 400D Digital with EF 50mm f/1.4 USM back focus issue post.

I took lot of my sister baby photos lately. I faced lot of fail to focus lock issue. I did not use flash on baby. I used ISO 800 and above in low light room. But still failed to focus lock sometime. Is this a common issue with Canon EOS 400D Digital?

I am not satisfied. Therefore, I did some test on it. I took wall as sample. I cannot get a focus lock with built-in flash and without even with ISO 1600. Same applied to plain surface. However, I could get focus lock easily with my Canon Speedlite 580EX II even in very low light environment. Below is the shot I take with Canon Speedlite 580EX II. Is my Canon EOS 400D Digital having focus issue? Or just Canon Speedlite 580EX II is too powerful in focusing?

Shot with Canon Speedlite 580EX II

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5 Responses

My Canon EOS 400D Digital and EF 50mm f/1.4 USM are backed! by Jayce Ooi’s Paradise

October 9th, 2007 at 10:42 pm
1

[…] Related topics: Check Canon EOS 400D Digital with EF 50mm f/1.4 USM back focus issue Focus lock issue with Canon EOS 400D Digital […]
Check Canon EOS 400D Digital with EF 50mm f/1.4 USM back focus issue by Jayce Ooi’s Paradise

October 9th, 2007 at 10:42 pm
2

[…] Related topics: My Canon EOS 400D Digital and EF 50mm f/1.4 USM are backed! Focus lock issue with Canon EOS 400D Digital […]
Jayce

October 10th, 2007 at 9:50 am
3

I got this reply from Doug Pardee at dpreview forum.

JayceOoi wrote:
> I used ISO 800 and above in low light room.
> But still failed to focus lock sometime.

Autofocus is separate from ISO. The autofocusing system requires a certain minimum amount of light to operate.
> I took wall as sample. I cannot get a focus lock with built-in flash

The autofocus system looks for a contrasting edge within the AF sensor area. A wall has no contrasting edges. A door frame (white wall with a dark area behind it) would be SO much better.

The built-in flash won’t help here. It’ll add light (through that terribly annoying sputter of AF-assist flashes), but it can’t create a contrasting edge.
> even with ISO 1600.

Again, ISO is irrelevant to autofocus.

> Same applied to plain surface.

Again, no contrasting edge.

> However, I could get focus lock easily with my Canon Speedlite 580EX II

The AF-assist function in the Speedlite throws lines of light onto the subject, thus creating contrasting edges.
keeyit

October 10th, 2007 at 3:04 pm
4

wow.. it is clear ! sure lol expensive camera lel
Jayce

October 10th, 2007 at 3:14 pm
5

Still ok la…