6d Focusing Problems

[perklax]

Hello,

I've recently purchased a 6d. It's a great camera and I love the look it has, but I'm having all sorts of troubles focusing. I mainly do portraits, and that requires me to consitently hit sharp focus on the eyes. For the life of me I can't do that. I'll focus on the eye using the middle autofocus point and then will recompose and take the picture, but it still won't work. It works half the time, but that's not good enough at all. It's been driving me crazy and I can't confidently go into a shoot. I'm getting paid for shoots also, so this isn't acceptable. 

[perklax]

Thanks to everyone. Appreciate the help!

[Waddizzle]

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@perklax wrote:

I only use the primes actually. Never had the zoom. But when shooting vertically oriented portraits, I usually have to focus with the outermost one, which has almost always caused a soft image. 

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If you are selecting just a single AF point with a 6D, you will get best results with the center point.  The remaining 10 points are useful for the "Basic" modes, and are practically useless in any of the "Creative" modes.  Stick to using just the center point in Creative modes, and you will get better results.  I say, focus and recompose.  Others, say not.

If you want "PRECISE" focus for portraits, you will not get consistent results relying on the camera's AF system.  The reason is really simple.  The AF system is not very exact, because like all electronic systems there is some error..  The AF system has a margin of error, and that margin error is nearly as large as the DoF with wide apertures at short distances. 

Exactly where the camera locks down focus can vary slightly.  Manually focus for the most ciritical shots.

[Peter]

Correct me if I am wrong.

Perklax uses a 85/1,8

The angle of view is 16 degrees on the short side and 24 on the long side. 28 degrees diagonal.  If you make a huge recompose about 10 degrees at 150 cm you will get the focal plane 2,28 cm away from you. At 150 cm and a 6D with 85/1,8 the "acceptable" depth of field will be from around 148.33 cm to 151.71 cm

If the recompose will be a smaller one, maybe the half of it ( the difference between the center point and the one most far away?) the focal plane will move around 0,57 cm away with 5 degrees. Acceptable? Only you can decide that, but every photographer should know what will happen when you recompose.

[Waddizzle]

"If the recompose will be a smaller one, maybe the half of it ( the difference between the center point and the one most far away?) the focal plane will move around 0,57 cm away with 5 degrees. Acceptable? Only you can decide that, but every photographer should know what will happen when you recompose" 

http://www.learn.usa.canon.com/resources/articles/2015/tips-for-getting-sharp-images.shtml

You are making the assumption that the plane of focus is flat.  For many lenses, it is not.  Try taking a picture of a wide wall mural sometime, or a wide, large, flat side of a building.  The outside edges can become out of focus.  Something similar happens when people try to "scan" old photos by taking pictures of them, and the edges are out of focus. 

Unless you have a macro lens, then the plane of focus is most likely not a perfectly flat plane, but more of a curved surface.

But, all of this moot, because if you want your "PRECISE" focus, then you probably shouldn't be relying on the camera's AF system to perform the focusing for you.  If you want "PRECISE", then focus manually.

[EDIT]  The curved plane of focus applies at both ends of the lens...what is going into it at the front, and what is coming out of it at the back.  The focus plane of the subject, and the focus plane of the image being projected onto the image sensor. 

[perklax]

[perklax]

A lot of it is stuff like this. Nothing is in focus and it's all blurry. Settings were 1/150th, f/5.0 and iso 1000. I made the shutter longer to account for the fact that I was missing focus, which I thought was that I wasnt stopped down enough. But I'm not sure what the real problem is. Motion blur?

[Peter]

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@perklax wrote:

A lot of it is stuff like this. Nothing is in focus and it's all blurry. Settings were 1/150th, f/5.0 and iso 1000. I made the shutter longer to account for the fact that I was missing focus, which I thought was that I wasnt stopped down enough. But I'm not sure what the real problem is. Motion blur?

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Seems like camera shake to me. But at 1/150 you should have made it without any problems. Try a tripod or monopod.

[perklax]

That's what most of the out of focus looks like. It looks like slight blur and then a lot of noise is added also

[Waddizzle]

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@perklax wrote:

A lot of it is stuff like this. Nothing is in focus and it's all blurry. Settings were 1/150th, f/5.0 and iso 1000. I made the shutter longer to account for the fact that I was missing focus, which I thought was that I wasnt stopped down enough. But I'm not sure what the real problem is. Motion blur?

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What focal length?  Subject distance?  Here is a depth of field, online calculator.

http://www.dofmaster.com/doftable.html

It does look a little soft.  I think the first thing to correct is the high ISO. You are definitely losing detail.  Drop the ISO as low as you can squeeze it.  Don't be afraid to open up the aperture, either.  Use the above link, to help guide you in setting up shots. 

A tripod can take camera motion out of the equation.  I would also use the tripod to level the camera, too, for these types of shots.  Look at the brick lines.  Use a remote shutter switch, or the camera's shutter delay timer, to further eliminate camera motion.

[perklax]

Yeah I jacked up the iso because I thought that the wide aperture was the problem, so maybe that's another thing to focus on. And yeah the bricks are an issue. I straightened them after the fact. But this was using the 50mm at around 8-10ft.