Yesterday, I did a little experiment. I put the camera back to factory settings, and I put it in Auto mode. My husband took a picture of our son, then I stood in the exact same spot and took an identical picture of DS.
My husband's photo is tack sharp. My photo? DS's ears are nicely in focus, but his face is out of focus.
So I dragged it to the closest camera shop (which is a Ritz) and the store clerk and I did the same thing with the same frustrating results. The only advice he gave me was to keep practicing. (I have taken hundreds of photos with this lens, trying to get it right.)
It is obvious that the problem is me, not the lens, not the camera, not the focal point.
Does anyone have some advice? I'm ready to give up.
To give you an example, lets say you're standing 5 feet away from someone with your F-stop set to 1.8. If you very carefully focus on their eyes, it is very possible that their ears may be slightly out of focus because the focal length is THAT short. Its fine and good to do that, just be aware that you have to be VERY precise with this method, and it is of course best to always focus on the eyes. Just a note as well, that the further back you are from your subject, the more apt you are to have more area in that tack-sharp focal area.
(Another note that the blur you're seeing is referred to as "bokeh" - the ever-desired blur for the wide-open f-stop that you get with prime lenses. Its beautiful in background to make your subject pop out of the frame, but when misplaced can appear "blurry" rather than done on purpose)
HOWEVER, if you set your f-stop to 5.6 or above, you will likely have their entire head in focus, and be more likely to have that tack-sharp look over more depth. To better explain this, you could have sharpness from the front of the nose all the way back to the ears without a problem, and your background will still have some bokeh (though it won't be AS much).
A good way to play with this is to set your camera settings to "aperture value" (AV on Canon cameras - on Nikons it is simply A). Then you can manually adjust your aperture, testing out the different focal lengths, while your camera adjusts appropriately for shutter speed and ISO.
ETA: It might be a good test for you to set up a scene (say a bowl of fruit on a table or something else that won't move), and try taking pictures of it one after the other with different aperture settings to see what the difference is with the blur (bokeh) and focus effects. Just make sure to have good lighting (such as a wide north-facing window or in an open garage) so that your shutter speed is at least 1/100 of a second, since anything lower can take away from that "tack sharp" look you're going for. You can help this by upping your ISO if you see your shutter speed is going below 1/100 on an automatic setting.
Hope that helps a bit.
your focal point is what needs adjusting. What I do is use the center focal point, hold down half way to focus on what I want and then move the camera to compose the shot. If you pair that with setting your shutter speed to 250 or higher (so you can freeze movement while hand-holding your camera) you should be good.
GreenMama has another good point about depth of field. When you set your shutter to 250, you're going to end up with much bigger aperatures (lower numbers). So, you'll have a shallow depth of field with this method, but you will have focused images. Standing further back will help to get a whole face, for example, in focus and you can crop down to the ideal size later...
Proud Mama to West - a delightful 3 yr old who loves to and . Excited for a new little bean in late April 2013!