[JamieP]

Looks like the 1/500 shutter speed is fast enough to freeze any slow movement on the subject; it appears to me that there is a slight BF issue with the lens. Also, I would use AF.S in this case as you would want to camera to lock the focus once you nailed it. I would also use AF selective point to avoid any movement of the camera; just my 2-cents.

I agree that motion blur is not the issue. I'm thinking it was motion between the time that I locked the focus and took that shot that moved his face/eyes in front of the area of sharp focus.

I tested the lens in the past and then again after this shot and feel pretty confident that it isn't a BF issue.

[Kerrowdown]

I'm just old school, it's all in eyes, if you get them right, the rest kinda falls into place.

[Class A]

switch to AF.C and keep an AF point on his eye while holding the shutter at half-press. When you see the expression you want, click !

Exactly. That's what all the AF points are for.

Recompostion also introduces a slight focusing error which, however, is rather negligible in most situations. I'm still puzzled why so many swear by the centre-AF point + recomposition even if that means that they'll lose time and sometimes focus in the process.

[Marc Sabatella]

Exactly. That's what all the AF points are for.

Recompostion also introduces a slight focusing error which, however, is rather negligible in most situations. I'm still puzzled why so many swear by the centre-AF point + recomposition even if that means that they'll lose time and sometimes focus in the process.

Good question. I'd say it's because the flip side is the possibility of missing shots because you've forgotten the focus point is somewhere other than center, or you can't work the fiddly little buttons fast enough to get the focus point where you want it. Or you just get tired of having hit buttons before every picture. Presumably, people accustomed to using the selectable focus points would scoff at this and say it isn't a problem in practice once you get used to it. I have no trouble believing that; I'd just observe that I could say the same about criticisms of center point focus-recompose...

[Rich_A]

switch to AF.C and keep an AF point on his eye while holding the shutter at half-press.

Another vote for this process.

I shoot lots of portraits just like this one and this is exactly the process I use to solve the dilemma you described. The only thing I modify is the ISO to match the lighting and to maintain a shutter speed of around 1/60 to 1/250 sec. depending on the subject's movement. Trying to refocus and recompose and snap the pic with a moving subject at close distance is simply too slow and clunky in my experience, not to mention frustrating when you miss that "perfect shot". I shoot with center AF point for landscape and recompose, but then again, I don't think that pine tree is going to run anywhere.

[Class A]

I have no trouble believing that; I'd just observe that I could say the same about criticisms of center point focus-recompose...

Marc, I didn't say "I don't understand why someone doing 'centre-focus & recompose' doesn't get it and switches to non-centre AF point usage". I believe that everyone should do what works best for them. I just expressed my puzzlement regarding the high number of posters I see reporting on their "centre-focus & recompose" technique. After all it costs money to support multiple AF points and for most they seem just superfluous. Entirely my problem, no criticism towards anyone else.

[Barnster]

I shot the picture below with my Sigma 24-60 at 35 mm, 1/500 and F 2.8. I wanted to shoot it wide open to really make my son pop from the background. I really liked it on the lcd preview (of course), but was disappointed once I got it on my computer. I think I missed the focus- it looks to me that the hair on the very top of his head is sharp, but his face and eyes are soft. My son was acting very silly when I took this, which means he wasn't holding still. Is 2.8 to shallow to use in a situation like this when the subject is moving around a bit?

I'd appreciate any thoughts on whether the focus is what's lacking in this shot and suggestions about how to prevent missing shots like this in the future.

Thanks in advance!

For a portrait you really woudn't go below f5.6,and focus up on the eye area,then click away.Going to f2.8 you run the risk of anything beyond the nose,eye area not be sharp.Experiment,try different f stops.You'll work on something that you'll be satisfied with.Just Practice,practice,practice!!!

[Andreas]

Marc, I didn't say "I don't understand why someone doing 'centre-focus & recompose' doesn't get it and switches to non-centre AF point usage". I believe that everyone should do what works best for them. I just expressed my puzzlement regarding the high number of posters I see reporting on their "centre-focus & recompose" technique. After all it costs money to support multiple AF points and for most they seem just superfluous. Entirely my problem, no criticism towards anyone else.

For me the biggest drawback is the fact that these other focus points are slower than the central one. The autofocus of my Ds is slow; focusing with the non-central points is even slower and therefore no option in many situations. (That's my only reason to long for a different camera.)

But as said -I don't think that focus-recompose has anything to do with the problem here, the DOF must be about 2 cm (less than an inch) -about 1 cm in both directions. Any move will hurt. (And stopping down to f/4 won't help much.)

[JamieP]

For me the biggest drawback is the fact that these other focus points are slower than the central one. The autofocus of my Ds is slow; focusing with the non-central points is even slower and therefore no option in many situations. (That's my only reason to long for a different camera.)

But as said -I don't think that focus-recompose has anything to do with the problem here, the DOF must be about 2 cm (less than an inch) -about 1 cm in both directions. Any move will hurt. (And stopping down to f/4 won't help much.)

I think the DOF was thin, but not that thin. I think I was a bout 4 feet away. According to the calculator in the lens forum, that puts my DOF at:

Near limit 3.79 ft
Far limit 4.23 ft
Total 0.44 ft

In front of subject 0.21 ft (47%)
Behind subject 0.23 ft (53%)

I'd have to be inside 2 feet away to get the DOF you mention.

[Lowell Goudge]

a couple of points of DOF

first of all, it is not equally divided by in front and behind. it is 1/3 in front 2./3 behind

second, it is based upon a specific image size, roughly 8 x 10 inch.

if you enlarge ebyond this DOF is reduced because DOF is defined as acceptible focus, not perfect focus

[Andreas]

I think the DOF was thin, but not that thin. I think I was a bout 4 feet away. According to the calculator in the lens forum, that puts my DOF at:

Near limit 3.79 ft
Far limit 4.23 ft
Total 0.44 ft

In front of subject 0.21 ft (47%)
Behind subject 0.23 ft (53%)

I'd have to be inside 2 feet away to get the DOF you mention.

Indeed, I assumed about 1.75 feet. That makes a difference! I think I'll have to dig up my FA 35mm to get the feeling again.

[Andreas]

a couple of points of DOF

first of all, it is not equally divided by in front and behind. it is 1/3 in front 2./3 behind

second, it is based upon a specific image size, roughly 8 x 10 inch.

if you enlarge ebyond this DOF is reduced because DOF is defined as acceptible focus, not perfect focus

Lowell, this 1/3 and 2/3 is just a (very general) rule of thumb. In this case it's more like 50/50. (But indeed DOF depends on other assumptions too!)

[D4rknezz]

Wow nice picture!!

I dont know much about the answer to the question, but you can definitely work on this picture just as suggested, post-processing it by making the hair blurrier, and sharpening the face to bring out the eye.

[Lowell Goudge]

Lowell, this 1/3 and 2/3 is just a (very general) rule of thumb. In this case it's more like 50/50. (But indeed DOF depends on other assumptions too!)

actually no, it is not a rule of thumb but a law of optics, distorted by non ideal characteristics of some lenses, that can in specific cases make it appear to be more 50/50. one of these points is the lack of sharpness of lenses wide open.

[JamieP]

actually no, it is not a rule of thumb but a law of optics, distorted by non ideal characteristics of some lenses, that can in specific cases make it appear to be more 50/50. one of these points is the lack of sharpness of lenses wide open.

I have no expertise in this area, but will offer the observation that from playing with the DOF calculator the % in front vs. % in back of subject change with the focal length of the lens, size of the sensor, apperture and distance to the subject. This does not seem to support the statement that the 1/3 in front and 2/3 behind is a law of optics.

If it is a law of optics, please explain how I should be interpreting (or ignoring) the results from the DOF calculator: Online Depth of Field Calculator

Thanks