Canon 50mm 1.4 needs focus adjustment?

[davidkenedy]

<p>I have a Canon 50mm 1.4 that seems to have a focusing error, the AF works fine but the spot that I focus on will always looks very slightly soft through the viewfinder, but in the resulting image that spot comes out tack sharp. And if I try to manually adjust and fine tune the image in the viewfinder to have my subject look sharp, the resulting image comes out very slightly blurry.</p>

<p>It's really weird, and I have no idea what the problem is or how to fix it. Anyone have any ideas what this is?</p>

[JDMvW]

<p>I'm not saying that this is your problem, but USUALLY when this occurs, people have forgot about the focus adjustment on the finder eyepiece. Of course that should affect <em>all</em> focus, but I suppose it might be more obvious at 50mm. :|</p><div></div>

[JDMvW]

<p>More obvious at f/1.4, that is.</p>

[davidkenedy]

<p>Ah yes, sorry I totally forgot to mention that I tried that and it doesn't seem to be the problem. I will get the diopter to where I can see everything very clearly but the manual/AF discrepency is still present. Thanks though!</p>

[PuppyDigs]

<p>Might need to reseat your focusing screen. Sometimes they get knocked slightly out of alignment. My EOS 3 used to need reseating as did my 5D. Realize your camera was designed for AF and the focusing screen isn't 100% accurate for MF. If you're really picky you can slim it to correct for the slight misalignment.</p>

[davidkenedy]

<p>I took it out and reset it back in there but the problem is still there. What do you mean slim it?</p>

[PuppyDigs]

<p>That's a typo. I meant to type shim, i.e., place a small spacer in the screen bracket to tweak alignment with the focus plane.</p>

[davidkenedy]

<p>Oh wow, ok that sounds tricky. Have you done this?</p>

[phule]

<p>Does your camera have Live View? If so, how does the focus look on the LCD after you AF the lens?</p>

[davidkenedy]

<p>Yeah it has Live View, its a Canon 5D mkII, with Live View the problem is still there. In fact I can detect it even more because of the digital zoom feature. If I center point AF on a contrasty subject with lots of detail I can zoom in digitally quite a bit and see that it is actually very slightly out of focus. Yet the resulting image is sharp. If I adjust manually while digitally zoomed in the subject becomes crystal clear on the screen, but the resulting image is softer. This is kinda driving me nuts.</p>

[PuppyDigs]

<p>Hmm, your escalating description to starting to sound more like "focus shift" than inaccurate screen placement. Some lenses exhibit a different point of focus stopped down than when wide open. </p>

[davidkenedy]

<p>Don't some higher end cameras have a focus fine tuning feature? I've heard about this somewhere but can't remember what it is actually called.</p>