Need focus help!

[janestudios]

I am self-taught and shoot with a Canon 5D with my 50mm f1.4 or my 24-105L lens. I tend to center point focus (AF) and recompose. I always seem to be out of focus on the eyes and tend to pick up the shirt front or lower ground etc...

I have been reading about back button focus, but cannot figure it out on my 5D (I even went to Canon's site and am still not finding specific instructions for the 5D) and was hoping for some advice from some real focus pros.

Again, Iam looking for options and am open to hearing what you all do (except manual, I am not ready for that and have bad eyes anyways!)

Thanks for taking time to answer this. I am usually desperate if I turn to my forum instead of googling everything

[LoveDSLR]

5D does not have the feature of lens fine tuning like the 5D2. You may have to send the lenses back Canon for calibrations.

Are you sure they are both front/back focus? You can try the 45 degree test (e.g., Focus Testing - photo.net or Nikon D70 Focus Chart). Otherwise, you may have to practice more on the focus and compose technique.

[SandeeWig]

Hi Jane,
I used to do the same thing (focus-recompose) and never had any trouble with that until I got my dSLR. After inquiring about essentially the same thing on this forum, a user pointed me to this article, which explains in some detail about how that method can often cause focus problems because of the change in the plane and arc of what you originally focused on, compared to where you end up after you recompose.

I had to read it a couple of times to really get it but it did finally sink in. Here's another article I found in searching for the original one; I glanced at it and it says essentially the same thing, but does indicate that focus-recompose doesn't always fail, depending on your aperture setting and focal length.

I suspect if you're shooting anywhere near wide open on your 1.4, then focus-recompose is exactly what is causing your problems. Ever since then, I have predetermined my focus point and composed around that point and it has made all the difference.

All the best...

[janestudios]

Thanks for the advice you all. I actually read the second article myself yesterday, I understand what it is saying (although doing the math in my head is difficult!). So I am hearing a lot of new info, like back button focus or sharper aperture and focus center.

Any additional thoughts anyone on a better technique?

[janestudios]

I think I will have to call canon and check the lenses out and see about recalibration. I read a few people that have had to do that.

thanks!

[LoveDSLR]

Originally Posted by janestudios

Any additional thoughts anyone on a better technique?

I practiced focusing (and lighting techniques) on a mannequin head (that was decades ago) and I have no problem focusing my 85 f/1.2 on 5D & 5D2 using the center focusing point (focus & recompose).

[kencaleno]

Try setting auto focus on single shot-then shutter won't fire unless focus is spot-on. have you adjusted the dioptre? Ken

[kencaleno]

Originally Posted by SandeeWig

Hi Jane,
I used to do the same thing (focus-recompose) and never had any trouble with that until I got my dSLR. After inquiring about essentially the same thing on this forum, a user pointed me to this article, which explains in some detail about how that method can often cause focus problems because of the change in the plane and arc of what you originally focused on, compared to where you end up after you recompose.

I had to read it a couple of times to really get it but it did finally sink in. Here's another article I found in searching for the original one; I glanced at it and it says essentially the same thing, but does indicate that focus-recompose doesn't always fail, depending on your aperture setting and focal length.

I suspect if you're shooting anywhere near wide open on your 1.4, then focus-recompose is exactly what is causing your problems. Ever since then, I have predetermined my focus point and composed around that point and it has made all the difference.

All the best...

Here's my take:

NOTE: In your camera’s viewfinder, depending on camera-flagship models generally have many focusing spots, and lesser, entry-level dslr’s will have around 5 focusing spots. With lens wide open, any of these spots can be used for selecting where to auto focus-But, depending on maximum aperture of lens in use, the ones you are able to use get fewer. Top-of-the-line cameras will only have the centre spot usable at F8,and entry level cameras at F5.6, and less than that, even these single spots aren’t reliable.]
Actually it is more beneficial to set auto focus by the centre spot, then re-compose, rather than use the peripheral spots-The reason being that only the centre spot has vertical and horizontal pixel rows. This means that if you use the peripheral spots (top and bottom spots have horizontal pixels only and right and left spots have vertical pixels only) To focus, you must have a part of the scene crossing a line of pixels at 90 degrees, and the centre spot gives you a more accurate reading ,having both vertical and horizontal pixels)

[sybren]

Originally Posted by kencaleno

Actually it is more beneficial to set auto focus by the centre spot, then re-compose, rather than use the peripheral spots-The reason being that only the centre spot has vertical and horizontal pixel rows. This means that if you use the peripheral spots (top and bottom spots have horizontal pixels only and right and left spots have vertical pixels only) To focus, you must have a part of the scene crossing a line of pixels at 90 degrees, and the centre spot gives you a more accurate reading ,having both vertical and horizontal pixels)

This is probably true for Nikon and maybe other brands. However, Canon uses cross-type sensors for all the AF points.

[LoveDSLR]

Originally Posted by sybren

This is probably true for Nikon and maybe other brands. However, Canon uses cross-type sensors for all the AF points.

Unfortunately my cheaper Canon 5D2 and 5D use one cross-type sensor in the center only while my Nikon D300 has 15 cross-types.