Wednesday, September 22, 2010

I Have a Photography Question!!!

Seriously y'all, I need your help. I've been noticing something when I'm shooting with my Canon 50mm f 1.8 lens, and I'm honestly not sure whether this is normal, or indicative of some other problem. Here's the deal--when using auto-focus, I have been noticing that the focus is good at about 2-3 feet, but beyond that, it isn't as sharp, even when the auto-focus has "locked" onto a point.

Take a look at these--all images were shot at f. 1.8| 1/100th sec| 800 ISO. All were set to focus on the middle point, which I aligned with the lamb's eye. In each case, I got the red "locked" focus point. 

2 Feet

4 Feet

6 Feet

Here's the 6 Foot shot cropped closer: 

The focus is significantly less sharp at 6 feet compared to at 2. Is this normal for using auto-focus?


  1. It might have to do with your ISO setting since the cropped in at 6 feet looks grainy more than straight up blurry?

  2. One thing I've noticed with my 50 mm is that it's not always sharpest at 1.8...try backing it up to say 2.8 (same thing with my 28-75 mm, I shoot at a minimum of f/3.2 rather than 2.8). Each lens has it's own sweet spot and you may just need to experiment to find yours.

  3. Yes, in my admittedly meager experience, that is the case. At least, that's what we told folks at OfficiusMaximus when they asked. Who knows; I could've been lying them the whole time. I lied about plenty of other things. Reasons their ink cartridges didn't work, for example. Generally, the reason for that is either "cuz you screwed it up" or "planned obsolescence," neither one of which customers like to hear. But I digress.

  4. I think it's a mix of both the ISO using the auto-focus with such a small aperture. 1.8 is a very narrow depth of field or area of focus. It all depends on what your auto focus internally is focusing on. In the 6' photo it looks like it's locked on your couch buttons so that's what's going to be in focus, nothing else will be as sharp. Take that same shot at f32 and everything will be in focus. Try using the 1.8 with manual focus and you'll have much better luck.

    Anywho, hope that rambling makes sense.

    Oh, and hi! I've been a lurker for a while, but couldn't resist putting my two cents in on this one.

  5. Lots of good information on how the Canon system works can be found here:


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