How do I focus when the AF is poor?

I love my 50mm 1.8 for its sharpness when focused properly. But with my lens, and I believe it's quite common for that model, the AF gets pretty useless for any distances over 5 feet it seems. That is, it focuses short of what I'm aiming for - and I am using the centered single point.

AFAIK there is no way to calibrate the AF of my lens (please correct me if I'm wrong).

Are there any great tips/techniques for getting fast and accurate focusing with such a lens? I have been trying to focus manually but struggle to get it perfectly focused based on what I'm seeing in the viewfinder, especially when I'm shooting with a low DOF.

Some camera bodies permit "micro-adjust" on the AF, but you don't say what body you're using. There's no reason why the AF should be poorer at longer range. Are you using it in low light (where it is often said to be a poor focuser), or against low-contrast targets, where the AF has nothing to work with? Bear in mind that when your DOF is very thin, not much of the image will be sharp, which can give the impression of an out-of-focus image. If your shutter speed is slow, small amounts of camera shake can look the same as poor focus. If you want a better diagnosis you need to show an example of the kind of image you are unhappy with.

In low light, like indoors at night when only one lightbulb is on, even my 1D2 struggles to focus at the center AF point (set to center AF with no neighboring AF points, ONE SHOT). It would focusing forward and back forward and back, which was frustrating since my 24-70 can easily nail it. I was focusing on something with contrast, such as a furniture against a white wall. I just ended up using manual.

Madweasel wrote in post #10625104
Some camera bodies permit "micro-adjust" on the AF, but you don't say what body you're using. There's no reason why the AF should be poorer at longer range. Are you using it in low light (where it is often said to be a poor focuser), or against low-contrast targets, where the AF has nothing to work with?

The body is the 450D/XSi.

Poor AF is the case both in good and bad lighting.

I'll try to take a few test shots for demonstration.

Go manual if you have live view or something that lets you zoom in and focus.

Eventually you'll get a feel for the DOF as you watch it shift back and forth while twisting the focus ring, and you'll be able to manual focus through the view finder fairly accurately by 'landing' the sharp area on the subject.

Of course this has its limitation for fast action and opportunity shots, but once you get the muscle memory down for manual focusing it is pretty fun

Besides manual focusing , there's not much you can do with this lens. I suggest replace it with another one of the 50mm lens.

CountryBoy wrote in post #10625511
Besides manual focusing , there's not much you can do with this lens. I suggest replace it with another one of the 50mm lens.

And judging from your signature it looks like you've had some bad experiences with the 50mm 1.8 AF as well?

My AF was fine, but it seems to be the first thing to go if you drop it or do other damage to the lens. Mine split in half and, though I was able to put it back together, the AF is completly gone now. It's MF for me and I can do well with that in certain circumstances, but it really stinks (so slow) in other ones.

PhotoCupcake wrote in post #10625568
And judging from your signature it looks like you've had some bad experiences with the 50mm 1.8 AF as well?

Yes, it took a few to get one that was usable wide open , none really had a great or good AF.

Here are 100% crops of three test shots that I did with ISO 100 f/2.5 1/200s and flash bounced by ceiling. The distances noted aren't accurate as the camera was positioned behind the zero line and obviously above. They are relative, i.e. 30 was closest, 60 middle, 90 furthest away. The paper pieces show where my focus point was.

No sharpening was done aside from default RAW conversion.

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YankeeMom wrote in post #10625599
My AF was fine, but it seems to be the first thing to go if you drop it or do other damage to the lens. Mine split in half and, though I was able to put it back together, the AF is completly gone now. It's MF for me and I can do well with that in certain circumstances, but it really stinks (so slow) in other ones.

Mine has been this way out of the box. And yes, it is capable of taking great photos with MF, but it's just not versatile enough for most situations, I find.

The 50 is really a toy, my 85 never came off my camera until I got the 50 3 weeks ago, then last week I put the 85 back on. It handles low light much better. The auto focus is sharp quick and bugless. It produces better pictures and is more durable. Go with a better lens such as the 85 but if you like primes there is also the 35L 100 macro etc.

Funny thing about the Mk II, the AF and MF both suck, and it can all be attributed to the build.

The focus is definitely off on your copy of the 50mm. That lens would work great on a camera with micro-focus adjustment.

EGO_09_BOI wrote in post #10625801
The 50 is really a toy, my 85 never came off my camera until I got the 50 3 weeks ago, then last week I put the 85 back on. It handles low light much better. The auto focus is sharp quick and bugless. It produces better pictures and is more durable. Go with a better lens such as the 85 but if you like primes there is also the 35L 100 macro etc.

It's not a toy and the 85 is awfully hard to use in close quarters (on a crop camera.) Of course, if you can afford a more expensive version, the 50 1.4 is a good option -- but you will not see a huge improvement in quality.