How do you focus precisely with a big aperture and a body with no Live View?

Question

I currently shoot with the Canon XS, and often I have to turn to its Live View to have the 50mm focus on the person's eyes at f/1.8. When I try to both manual and auto focus through the viewfinder, I often miss.

I'm asking this question because I was looking for another body and some of my choices don't have Live View and I want to be able to focus at aperture 1.8.

If I have such a body then would my options only use a smaller aperture, or practice, brighter viewfinder, etc.

Answer 1

I'm surprised that you "miss". Auto focus on modern cameras is really rather good (providing you have enough light). I only use the center focus point. I focus (with a half press on the shutter), then recompose the photo and press the shutter all the way.

If I focus on the eyes, it works just fine.



Perhaps you are expecting a bit much DOF from your f1/8 lens - your DOF will be quite small, so no matter how accurately you focus, only SOME of your photo can ever be sharp.

Your bigger problem might be movement.... if you lock in excellent focus, but then either your camera or your subject moves a little bit, the focus will be out.

I doubt your camera is doing anything wrong at all.

Answer 2

Autofocus is almost always accurate, unless you're shooting in low light. Use the viewfinder for focusing, because the sensors in the viewfinder perform better. When focusing in Live View, it judges focus based off of contrast on the image sensor.

I don't understand how you can miss with manual focus. Unless you're closer than the minimum focusing range, it's possible. If your depth of field too small (for example, not all of the face is in focus), then use a smaller aperture (larger number). As long as you do that and your subject doesn't move, you can't miss.

Edit: Yes, a smaller aperture is better for full-body shots. Also, most lenses are sharpest a few stops smaller than their largest, that lens included. Just an added bonus.

Answer 3

If you miss focus at f/1.8 you must be medically blind. The lens is wide open already!



Additional Answer

No, you did not miss the eyes (which means you're not blind). Someone (either you or the model) moved. F/1.8 produces a very shallow DOF. Set to single focus at center then mount camera on a tripod with IS off. Use the self-timer to avoid any shake from the camera's end if you don't have a remote and yes, use manual focus only at such large apertures.

Answer 4

Your example is exactly why portrait photographers using large apertures don't use auto focus.



Live view is going to be harder to get fine focus with than looking through the viewfinder, with less than 1/10th the resolution of your capture, what looks focused on the screen could be quite blurred in the final print.



It's important to make sure the diopter adjustment on the eyepiece is set correctly.



Full body shots should just about be possible at f/1.4 with the focus properly set, definitely possible at f/1.8



Head or Head and Shoulder shots and you need to drop to f/1.8 / f/2.



You really need to learn to look around the frame while you are previewing and not concentrate on one spot (that's why auto-focus fails), and play with the focus. As it's digital you can also try minutely pushing and pulling (ie moving the focus point forward and back) in subsequent frames.



Get this right, and it won't matter what body you are using!



@Dansby, we're spoilt, Sony's A65 & A77 have modes that work slightly more intelligently than PREVIOUS generations of Canons' and Nikons', their next generation will catch up though.

Answer 5

If you are indeed attempting to manually focus (the other answers already explained autofocus) you need to make sure the body and lens are both set to manual focus first. You also might need to adjust your viewfinder to your eyes (there's a little dial next to it).



I don't know how the Canon works, but my Sony a77 does great with autofocus. It shows little green focus points when you half press the shutter and you can keep half pressing and they move a bit. Then take the photo when the green boxes are over the spot you want to focus on.

Answer 6

Considering 99.99% of professional photographers shoot without LiveView, I wonder what your problem is. If the autofocus isn't working for you (and we are often challenged with the camera can't read our mind and know exactly what we want it to focus on), we simply turn off the autofocus and use manual focus, via the all-important viewfinder.



Frankly, LiveView autofocus is usually contrast based, and is slower that regular autofocus. And nothing beats a trained photographer using careful manual focus.

Answer 7

If you are shooting with a SLR, then all you need is plenty of light to focus. However camera blur can come from other problems like vibration or very slow shutter speed. Always use a tripod if possible and use camera timer for steadying the camera.