Focusing Problems with Nikon 105 f/2 DC lens

Lonnie1212

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Hi Folks,

I am using the Nikon 105mm f/2 lens to take pictures of my grandchildren. In the two pictures included with this post I have the same problem. I focus on my granddaughters right eye in both pictures. But the face and eyes remain out of focus and the collar area is more in focus. The lens setting is on f/2 and I think the defocus option is on. I have taken pictures at f/5.6 and there are no problems. What could I be doing wrong? I would like to use f/2 because it produces awesome bokeh. But I cannot tolerate an out of focus eyes and face. Thank you, Lonnie
 

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Hi Folks,

I am using the Nikon 105mm f/2 lens to take pictures of my grandchildren. In the two pictures included with this post I have the same problem. I focus on my granddaughters right eye in both pictures. But the face and eyes remain out of focus and the collar area is more in focus. The lens setting is on f/2 and I think the defocus option is on. I have taken pictures at f/5.6 and there are no problems. What could I be doing wrong? I would like to use f/2 because it produces awesome bokeh. But I cannot tolerate an out of focus eyes and face. Thank you, Lonnie
Look in the viewfinder and ensure that the focus point is where you want it BEFORE releasing the shutter.
 
Look in the viewfinder and ensure that the focus point is where you want it BEFORE releasing the shutter.

It is good to hear from you Razky. What you are saying makes the most sense. I went back through the photos and examined the focus points. I have the focus points made visible in the menu settings. I can see the focus point on the picture after it's taken. The focusing system seems to be picking up on the red cape and the dress for some reason. Could it be the bright red color of the cape? I did notice that I had the camera focus set to AF-C with D-9, that is 9 point focus tracking. I use those settings for bird photography while the birds are flying. I set the camera to AF-S and the metering to spot metering. Will try more pictures later on.

Thank you,

Lonnie
 
Using an online DOF calculator, if you are 6 feet from your subject: f/2 produces about 1.3 inches in focus. At f/5.6 you've got 3.8 inches in focus. Must be very precise focusing at f/2, like tripod precise, and you can't keep a child still enough. Most likely the problem but you could check to see if your lens/body is back focusing

I'm sure the bokeh on that lens is nice at f/5.6 or f/8 - working with background distance

Isn't the point of a defocus control lens so that you can use a workable aperture for the subject and have more "OOF" OOF areas?
 
Common problem when folks get their first wide aperture/shallow dof lens. When you only have 1.3" of dof, don't let the camera guess which of 9 focus points you want to use, use a single focus point and place it on or below the eye. I use the same point for metering so use a bit of the zone system, ie, caucasian skin is about 1 stop brighter than middle gray, so I back button focus there and that locks focus then adjust the camera meter to +1. Bingo, dead on focus and exposure. Also, remember, with such a shallow dof if you or the kids move closer or further a total of 1 inch, you have lost focus. Take some shots on tripod of a stationary object and see if that is a factor. Also, even spot metering and recomposing can change the angle of the camera and the actual distance to the subject if you tip the camera a bunch.
 
Common problem when folks get their first wide aperture/shallow dof lens. When you only have 1.3" of dof, don't let the camera guess which of 9 focus points you want to use, use a single focus point and place it on or below the eye. I use the same point for metering so use a bit of the zone system, ie, caucasian skin is about 1 stop brighter than middle gray, so I back button focus there and that locks focus then adjust the camera meter to +1. Bingo, dead on focus and exposure. Also, remember, with such a shallow dof if you or the kids move closer or further a total of 1 inch, you have lost focus. Take some shots on tripod of a stationary object and see if that is a factor. Also, even spot metering and recomposing can change the angle of the camera and the actual distance to the subject if you tip the camera a bunch.

Thank you mrca. I was wondering of one of those 9 focus points wasn't hanging up on that bright red cap around her neck. I changed the AF-C to AF-S with one focus point and spot metering rather than matrix metering. Come to think of it. If I am photographing children, maybe I should use AF-C with one focus point and spot metering. ???
I appreciate the advice you guys give.
 

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