I hate my 50mm f/1.8 now

This lens worked fine with my XT it seems, but with my newly purchased 30D, it can never AF correctly. Why is this? It's backfocusing half the time under darker light. And I went back and made sure that the focusing dots were on the subject and not user error.

I used to like this lens, but now, I'm very frustrated with it. Could it be my 30D body? My other lenses focuses fine.

And this test shows that it works fine...

Shot with 50mm at f/1.8

Some lenses you need to adjust per body, try reading up on microadjusting for the 30D.

Aight ..that was weird.. post shows up LOL as i'm typing a reply to the first one..

In that case; which AF point are you focusing on? AF focuses by contrast, and cameras see in black and white. So I think the culprit is the black car - it's not seeing it as the exposure for the black car (at least from the cam's point of view) isn't light enough. That said, which AF point are you focusing on? From the look of this it's not the backfocusing - but the far right AF point.

Try holding down the asterix themed button (has an * on/over it) and changing your AF point for Center. To me it looks like the AF point is focusing towards the right more than the left.

Are these handheld shots? What was your shutter speeds at?

Kajuah wrote in post #6948851
Some lenses you need to adjust per body, try reading up on microadjusting for the 30D.

What? There is no microadjust with any XXD body before the 50D.

OP - I have no idea why your 50/1.8 is worse on the 30D than the Rebel, but I once owned a 50/1.8 and I found it to be incosistent. OTOH I cannot tell from your shots why they appear so soft. Presumably they are misfocussed, though the subjects are low contrast and it could be that the lens simply missed for that reason.

JeffreyG wrote in post #6948869
What? There is no microadjust with any XXD body before the 50D.

Not as a feature in the cam, but on test sheets there was (like the one he just supplied).

The first Mercedes shot was a tripod shot and I let the camera find the focus points (and the camera found the car, and focused there). The shot came out unfocused.

The second shot was handheld with the shutter at 1/640s. I used selective focus and pinpointed the focus on the badge area (center nose) of the car. It looked like it focused in the viewfinder perfectly.

I just bought this 30D used and I'm getting nervous that it might have issues or something.

sinitry23 wrote in post #6948852
Are these handheld shots? What was your shutter speeds at?

No shake, it's focusing, just not on the subject... weird...

How's it work with your other lens? Is the 30d in focus with that?
Could the glass (or filter) be dirty?

With the 18-55, no issues so far. I haven't tried my 28-105 yet, I'm gonna go out and try them under similar conditions.

So if the lens is fine on another camera, why do you hate the lens?

The fact its odd on the 30d leads to 2 possible issues. Possiblilty number one is that the 30d is in fact back focusing, but your focus chart does not indicate that (although that depends on you getting the 45 degree angle right). Possibility number two is that you use the 30d differently and this contributes to focus errors, if its a new camera to you, that could be more probable.

In the first shot the only contrast point appears to be half way back down the car with some refelction, so like someone already pointed out, maybe its not a contrasty enough subject for autofocus to work. This is why lenses still have and MF/AF switch. The 2nd shot certainly seems to have the same issue as it seemed to go for the grass in the background. The car fills most of the frame so I can only image the extreame outside points on the left and right being capable of finding a target, and they are over the grass.

One thing I have to pick up is you said "the focus points". If you are using all focus points then the camera will pick the easiest thing it can focus on, which may or may not be what you intended. You have 9 focus points, pick whichever one matches your intended composition and use it. Thats why Canon give you more than one.

KarlosDaJackal wrote in post #6949123
One thing I have to pick up is you said "the focus points". If you are using all focus points then the camera will pick the easiest thing it can focus on, which may or may not be what you intended. You have 9 focus points, pick whichever one matches your intended composition and use it. Thats why Canon give you more than one.

Well that's the issue, I focus on the car, and the car comes out unfocused. Like I said, in the first shot the camera found the car. In the second shot, I selectively chose to focus on the car. Neither came out focused.

What F speed where those shot at? can you give full EXIF data?

Can you try some test shots around the house? Maybe some cups or similar items.

Cotmweasel wrote in post #6949188
What F speed where those shot at? can you give full EXIF data?

First Pic:
Camera Make: Canon
Camera Model: Canon EOS 30D
Image Date: 2008:12:24 00:14:52
Flash Used: No
Focal Length: 50.0mm
CCD Width: 5.13mm
Exposure Time: 0.025 s (1/40)
Aperture: f/2.0
ISO equiv: 100
Exposure Bias: -1.00
White Balance: Auto
Metering Mode: Matrix
Exposure: aperture priority (semi-auto)

Second Pic:
Camera Make: Canon
Camera Model: Canon EOS 30D
Image Date: 2008:12:25 17:27:17
Flash Used: No
Focal Length: 50.0mm
CCD Width: 5.13mm
Exposure Time: 0.0016 s (1/640)
Aperture: f/2.2
ISO equiv: 100
White Balance: Auto
Metering Mode: Matrix
Exposure: aperture priority (semi-auto)