Hi All, Wondering if someone could offer some advice - I recently (1st Oct) purchased an Canon 50mm F/1.8 and got to use it in anger for the first time yesterday at a gig... Now - some of the shots are crystal clear, but on the vast majority the singer (or wherever is centre frame is out of focus, while the front of the stage (visible at the bottom edge of most pictures) is perfectly in focus, it's not a movement issue - as most shots were 120th + and the stage at the same disatance as the singer is also blurred. I was focusing using the centre AF point, which gets nowehre near to the stage in any shots... I'll post some pics up later to illustrate if required once my net starts working properly - but does anyone have any links to any self-test front/rear focusing tests? Not sure whether I should take it back to the shop... RwD
We had a couple threads about this a while back... Did you try searching? I remember someone posted links to guides on the subject as well as explained it in great depth.
Heh - thanks OleJ - i had tried searching but managed to spell focus with two c's... found a nice chart someone posted - cheers! RwD
There's also a battery test. Take three or more batteries, line them up in a diagonal line. Set the camera up, focus on the center battery, and take a few pics. This should quickly show whether the lens is focusing improperly, and is much easier to setup than a focus chart would be. You can use more batteries, like 5, or other items that can be easily staggered. How dark was it? I'm told that the 50 1.8 has a hard time focusing in low-light shots.
What aperture were you shooting at? If you were shooting at f/1.8, then it might be a matter of misfocusing rather then front focusing. The fact that some of the pictures are in focus points to that for me. Your DOF is rather small at 1.8 and your camera's AF might not be up to the task of following a moving target with such a small margin of error. Also were you using continuous focus or single focus? That makes a difference too, since in single it only focuses at the moment, and doesn't account for subject movement. Unless your subject is static, AF systems rely on a tad bit of play to work, since they can calculate only so fast. Which is why most people give the camera at least f/2.8 to work with, if not f/4. Or, are willing to accept a lower hit rate. Next time, try using a focus point on the part of the singer that is the most well lit, rather then the center on on his torso.
All great points. When I shoot concerts, I try to shoot at f4, use continuous AF, and use single point AF with it trained on the subjects face. There is a lot of stuff on a stage that can mess up the focus if you leave it to the automatic systems on your camera. Mic stands in particular piss me off regarding focus but that's just one example.
Set your camera up on a tripod and set the lens to MF and the lens to f/1.8. If you've got liveview use 10x mag to MF on a subject of your choice, something relatively small and contrasty in good even lighting (a ruler set on an angle or the three batteries set up as stuey mentioned is a good start), using the center point. Take a shot. Now, without moving the camera or adjusting the lens, swap over to AF. Depress the shutter 1/2, or use the AF lock button, to activate AF. If you hear the lens motor move and see the lens barrel move, right away you'll know it refocussed. Take a shot. Now bring both up in DPP/PS and view at 100%. If you notice a difference the lens is misfocussing, if not it's fine. The problem may be as Johnny said plus the fact the that 50/1.8 is a poor low light focusser, specifically in servo.
+1 What Vers said. That and the fact that the 50mm 1.8 isn't the sharpest lens to boot. I already have the 1.4 on my wish list I'm love having a prime. I use the 50 1.8 for lots of portraits. Now I just want a 50mm prime that draws nicer colors/contrast and sharpness
