Focusing question

[jimmy83]

Now I've switched to selecting a certain focus point using my 40d. Which is normally Center point. Pretty much all of my photos since have been of friends and family so I've been focusing on the eyes.

Bit of an odd question, but when you guys are shooting depending on the subject. What do you focus on? Is it normally the nearest point of the subject to the camera? For instance buildings and landscapes, where would you focus in this instance?

 

[Bristolian]

Irrespective of what I'm shooting I always focus on the bit that I want to be sharpest. For anything with eyes that almost always means focussing on the eyes but otherwise it really is dependent on what I'm trying to achieve.

Sorry I couldn't be more vague

 

[HoppyUK]

Now I've switched to selecting a certain focus point using my 40d. Which is normally Center point. Pretty much all of my photos since have been of friends and family so I've been focusing on the eyes.

Bit of an odd question, but when you guys are shooting depending on the subject. What do you focus on? Is it normally the nearest point of the subject to the camera? For instance buildings and landscapes, where would you focus in this instance?

You obviously want your main subject to be sharp, so if this is something with depth, ie some points nearer the camera than others, then the focus position must be decided in conjunction with depth of field considerations.

 

[jimmy83]

When focusing on eyes, how do you get both in focus?

 

[Phil789]

Depends on the depth of field (aperture setting) and the alignment of the subject to the focal plane of the sensor.

If you are shooting someone who is looking at you at an angle with a wide aperture like f/2.8, if you focus on the eye closest to you then you will probably find the other eye is slightly less in focus.

If the subject is looking straight at you (both eyes same distance away) then if you focus on one, the other should be focus too.

If you want more detail to be in focus that is at different depths within the photo (if someone is looking at you at an angle then one eye is further away as above) then you would need a smaller aperture, f/6.0 for example, as this would provide a larger depth of field.

Hope this helps

 

[HoppyUK]

When focusing on eyes, how do you get both in focus?

You need sufficient depth of field. That's the name for the the zone of acceptable sharpness in front of and behind the spot focused on, and it varies a lot. DoF is a key create control.

Have a look here http://www.dofmaster.com/dofjs.html It's a DoF calculator. Input your camera top left, and that sets the parameter according to the size of the sensor. Then input your camera/lens settings and focusing distance below, and the answers pop up on the right.

You'll notice that depth of field is increased when:
a) distance is greater
b) focal length is shorter
c) f/number is higher

You will also see that a) and b) cancel out if you maintain the size of the image by, for example, using a lens of double the focal length, but also move back to twice the distance.

Other things to note, there is always more DoF behind the focused spot than in front. At very close range it is close to 50/50%, like a tight head shot; at medium distances eg groups of people it is about one third in front and two thirds behind (hence the common phrase 'focus a third in') and with distant landscapes there is much more DoF behind the focused spot, all the way to infinity.

There are various little DoF calculators about, or phone apps.