Camera Focus

GregSD

Hi All-

I would love if someone could help me out with a focusing issue I am having. I am not a professional photographer by any stretch, nor am I trying to be. My photography consists of taking photos of my kids.

I use a Nikon D5100 and have recently purchased the 50mm AF-S 1.8g prime lens. I have started to notice the focus on some of the pictures seems off.

Here is a picture I took today, where my focus point was on his nose. Now I usually try and focus on one of his eyes, however I feel this photo best illustrates the issue I am having. When I open the file in Nikon ViewNW 2 it, shows the focus point his nose. But the nose is clearly out of focus. My focus mode on the D5100 is AF-C (continuous-servo AF) and AF-area mode is single-point AF.

ISO 200
1/160s
f/4.5
50mm AF-S 1.8g

Here is the photo out (shot in RAW, exported as jpeg)
Image removed

Here is what View NX 2 told me was my focus point
Image removed

Here is what looks like is in focus to me
Image removed

Any suggestions would be great. Ideally I want to rule out a focus problem with the camera or lens. Again, I usually focus on the eyes, however I thought this particular picture showed the issue the clearest.

Thank you for your time,
Greg

Here is what

pathfinder

Welcome to dgrin, Greg.

I agree that it looks like your camera is focusing behind the intended selected area for AF with your 50mm f1.8

Now what I would suggest, is to place your camera on a tripod, lock it down, use a cable release, and focus on a brick wall at 45 degrees ( or a yardstick at 45 degrees), with a mark to show where your AF point is. I would also turn off AI Servo, and see if you can repeat this back focus effect. If you can, then your camera or lens, or both, may need service. If you cannot repeat this effect with your camera on a tripod and a stationary subject, then I would suspect subject or camera movement as a likely explanation. Was this image shot as a single frame, or is it one of several frames shot in high speed frame rate? I use AI servo when shooting high speed image sequences, but not for individual frames, where I prefer One Shot AF. Frequently with AI servo the first frame is not as in focus as later frames, as the AF system homes in with subject movement.

I am always suspicious of movement unless the subject and the camera body are fixed in space as my first explanation.

Canon cameras never have this problem......... ( this comment is a joke, for those who cannot discern irony on the web )

One other comment, I personally avoid trying to focus on a nose, rather than eyes in a portrait. One really wants the eyes sharp, not the nose, and my camera's AF systems prefer to grab the sharper, more contrasty line of the lashes and the lid margins over the softer, organic, less distinct nasal margins. I suspect Nikon cameras do this also.

Grainbelt

pathfinder wrote: »

One really wants the eyes sharp, not the nose, and my camera's AF systems prefer to grab the sharper, more contrasty line of the lashes and the lid margins over the softer, organic, less distinct nasal margins. I suspect Nikon cameras do this also.

I expect this to be the case. It took me a while to learn that my camera was not capable of performing magic, and I needed to put the focus point on something with suitable contrast to lock focus.

divamum

Assuming Nikon-Canon lingo is the same, servo is likely the culprit here - if he moved even a little bit, the camera will have adjusted in response. I generally DON'T use servo for portraits - it always results in screeds of missed focus shots for me (YMMV, of course). I know some fashion pros like it because their model can keep moving, but it really didn't work for me at all. Especially when shooting shallow depths of field, I stick with one shot, single point - usually the point directly over the eye (and with Nikon's zillions of focus points that shouldn't be an issue).

A lot of times these small anomalies don't show up UNTIL you're shooting at shallow DOF. If you're shooting at 25ft distance f4/f8 etc... you'll likely get clean focus. Move in to 6ft at 2.0, and you can really see where you (or the camera) "missed". That said, I see you were at 4.5 above. Were you standing very close?

YMMV, but that's how it has worked for me....

GregSD

Thank you VERY much for taking the time to look at my thread.

When I took the photo above, I was about 2 feet away from him.

I took another one of him this morning, where I used AF-S (single servo) and single point. I focused directly on his left eye, however his shirt collar looks the most in focus. I was approximately 5 feet away from him.

ISO 400
1/320s
f/4
50mm 1.8g prime lens

Here is the photo:
Image removed

And here is ViewNX 2 showing me the eye is the focus point:
Image removed

I'm not sure what else to do, other than figure it is an error with the camera/lens. However if I set up a static object and use a tripod, the doesn't seem to be any problem with focus at all.

Any advice is very appreciated.

zoomer

Don't look at them so zoomed in.
If you hadn't zoomed in and said they were out of focus nobody would have thought so.
If everyone looked at their portraits zoomed to 100% like this everything would look out of focus .

Have you applied any unsharp mask to these photos?

Do the test for front or back focus, if it looks good just go shoot.

When shooting at 1.8 or 1.4 I always use servo it will give you many more in focus shots because it will take into account the slightest movements.
From 2.8 and smaller I switch to locking in the focus.

GregSD

Thanks for the observations.

No post processing on these photos yet.

I think you are right, part of the problem is my 27 inch iMac monitor displays the photos beautifully but also allows me to nit pick the focus.

zoomer wrote: »

Don't look at them so zoomed in.
If you hadn't zoomed in and said they were out of focus nobody would have thought so.
If everyone looked at their portraits zoomed to 100% like this everything would look out of focus .

Have you applied any unsharp mask to these photos?

Do the test for front or back focus, if it looks good just go shoot.

When shooting at 1.8 or 1.4 I always use servo it will give you many more in focus shots because it will take into account the slightest movements.
From 2.8 and smaller I switch to locking in the focus.

babowc

Greg, I think your most recent post looks right on with the focus..