AF Issues at extreme ends of kit lens

[SandeeWig]

Hey all!
I read the other thread posted about a very similar to issue to what I'm having all of the sudden, but thought I'd post my own thread here as I have a different camera and slightly different issue.

I have a Canon XSi that's about 3 years old. I noticed last night that at the extreme ends of my kit zoom (18mm and 55mm), the AF is not working (Single Shot mode, single focal point selected). If I zoom in/out slightly, it focuses fine.

I may be posting prematurely here, as I have not had a chance to test the AF on my 50mm or the other zoom lens I own (a 75-300mm) to see if it's happening elsewhere, but I'm wondering if you think it is the camera, or the lens that is giving the trouble?

If it's the lens, no problem, I can do w/o the kit - or easily replace it.
If it's the camera body, then what do I do?! It was a refurbished body, and I'm way beyond the warranty for it even if it was new...so, would I contact Canon directly and have to send it in for them to see if it can be fixed?

Anyone else have this problem and/or have suggestions as to how to fix this problem?

Really hoping it's not the body...ugh!!!

TIA

[SandeeWig]

Also, I'm plenty of distance away from my subject, so that's not an issue.
And, I'm using a speedlight in addition to ambient lighting. However, I've read alot that if it's too dark, and my shutter is too fast, then it won't take the picture. Could it be that I have my SS set too high (like 1/100) for it to find focus w/ the low ambient light in the room?

(this is why I don't typically use my kit lens in the house! lol! )

[inkista]

Low light is typically an issue when it comes to autofocusing. A lot of a camera's ability to focus has to do with finding contrast, and low light means less contrast. Try aiming for a sharp edge where black meets white. If you don't have this issue outside in bright sunlight, it's unlikely that the gear's at fault, it could just be the lack of light.

Also, was the autofocus assist from the flash being used?

Try posting an example unfocused image, with the basic exposure EXIF information and we can try to help you.

[Hill Country Hack]

Originally Posted by inkista

Low light is typically an issue when it comes to autofocusing. A lot of a camera's ability to focus has to do with finding contrast, and low light means less contrast. Try aiming for a sharp edge where black meets white. If you don't have this issue outside in bright sunlight, it's unlikely that the gear's at fault, it could just be the lack of light.

Also, was the autofocus assist from the flash being used?

Try posting an example unfocused image, with the basic exposure EXIF information and we can try to help you.

I agree with inkista, it seems a light issue. You can also reproduce the fault in the usual conditions, then shine a bright light at what you are trying to focus on and try again. If you get a good focus with the added bright light, then there ya go.

[dasmith232]

Hi Aimee,

The AF design requires enough "overall" light to work properly.

Regardless of what shutter/aperture you choose, it comes down to how much light is in the real-world scene and how much light can reach the sensor based on the maximum aperture on the lens. This is regardless of what shutter speed or aperture settings you select.

This means that your shutter speed selection is not an issue.

The 18-55 isn't a high-end lens, but it has an aperture of f/3.5 (when set to 18mm) and is plenty capable of focusing in a moderately lit room. So, you really should not be having focus problems unless you have an equipment problem of some kind. Plus, if "AF assist" is enabled on the Speedlite, then you should be able to focus with that lens in a VERY dark setting.

I'd say to definitely try your 50mm. (Is it the f/1.8 aperture?) It should be plenty fast enough to focus successfully. That could eliminate (or confirm) that the problem is with the lens.

To your other question, if the body needs repair, Canon has a pretty consistent repair policy. You've got to send the body in for them to even quote something; they won't even guess over the phone. Many repairs fall into a "flat fee" category and I'm guessing will be in the neighborhood of $250 - $300. At some point, you'll start to think about upgrading vs. repair.

[SandeeWig]

Originally Posted by inkista

Low light is typically an issue when it comes to autofocusing. A lot of a camera's ability to focus has to do with finding contrast, and low light means less contrast. Try aiming for a sharp edge where black meets white. If you don't have this issue outside in bright sunlight, it's unlikely that the gear's at fault, it could just be the lack of light.

Also, was the autofocus assist from the flash being used?

Try posting an example unfocused image, with the basic exposure EXIF information and we can try to help you.

Thanks, Inkista. Yes, the AF Assist from the flash was being used. I'll take some test shots tonite and post any relevant ones if I don't resolve the problem. Thanks so much!

Originally Posted by Hill Country Hack

I agree with inkista, it seems a light issue. You can also reproduce the fault in the usual conditions, then shine a bright light at what you are trying to focus on and try again. If you get a good focus with the added bright light, then there ya go.

Thanks for your input as well HCH. I'll try your suggestion also.

Originally Posted by dasmith232

Hi Aimee,

The AF design requires enough "overall" light to work properly.

Regardless of what shutter/aperture you choose, it comes down to how much light is in the real-world scene and how much light can reach the sensor based on the maximum aperture on the lens. This is regardless of what shutter speed or aperture settings you select.

This means that your shutter speed selection is not an issue.

The 18-55 isn't a high-end lens, but it has an aperture of f/3.5 (when set to 18mm) and is plenty capable of focusing in a moderately lit room. So, you really should not be having focus problems unless you have an equipment problem of some kind. Plus, if "AF assist" is enabled on the Speedlite, then you should be able to focus with that lens in a VERY dark setting.

I'd say to definitely try your 50mm. (Is it the f/1.8 aperture?) It should be plenty fast enough to focus successfully. That could eliminate (or confirm) that the problem is with the lens.

To your other question, if the body needs repair, Canon has a pretty consistent repair policy. You've got to send the body in for them to even quote something; they won't even guess over the phone. Many repairs fall into a "flat fee" category and I'm guessing will be in the neighborhood of $250 - $300. At some point, you'll start to think about upgrading vs. repair.

Hi Dave. I was in a small living room w/ a halogen stand up lamp on. I don't generally have issues focusing in there w/ my 50mm, but didn't think it'd be an issue w/ the kit lens either using the speedlight. The AF Assist lamp was working (unless I was trying to focus too soon after it fired...hmm...). Yes, the 50mm I use is the 1.8.

I was playing around w/ my baby last night when I noticed the problem. I'll spend some time tonite testing it after she goes to sleep to really figure this out. Really hoping its operator error, not hardware issues (camera, or lens for that matter).

And, thank you for your insight on Canon repairs. I was afraid it would be something like that. As much as I'd love a new camera....sheeeesh!

Thanks very much to all of you!!!! I'll let you know the results of my testing tonight.

[SandeeWig]

Well, after further testing in similar conditions using the kit lens, the 50mm 1.8 and the Tamron 75-300; it appears that the problem is the kit lens. It's definitely a low light situation, but not so low as to not be able to focus. Even when shining a light on the subject, the camera fails to attempt to focus - at all now - with the kit. Focusing directly at a light source, it fails to attempt focus.

The 50 and the 75-300 had no problems focusing, with or without the flash.

I'm going to test the kit lens outside tomorrow to see if it continues to have issues in good light. It's not a huge issue, as I mainly use the 50, but it is definitely going to be missed for everyday shooting. Easily replaced, but hardly worth it...time to start researching lenses...my birthday's in April, so maybe I'll know what I want by then!

Thanks again for all your help today!