Advise on focusing


#1
Hi all experts, need some advise on focusing please. I am using Nikkor 35mm f1.8 DX. When I tried to take pics with f1.8 using A setting, sometimes I am not able to get a sharp focus on the face for portrait shots after focus and then frame. The sharpness could be on the shoulder or chest area instead. I set my camera to AF-S and I press half shutter and hold and do framing. Could it be that the shutter speed is too slow? Please help. Thank you.
 

Dream Merchant

Moderator
Staff member
Jan 11, 2007
9,660
6
38
#2
We can't see the photo, and have no idea of what settings were used, and we also do not know what AF point(s) were selected.

Lets take a wild guess - either you were too close and beyond the lens' MFD, or the camera's AF points picked-up and locked on a brighter/more contrasty part of the frame.
 

catchlights

Moderator
Staff member
Sep 27, 2004
21,903
46
48
Punggol, Singapore
www.foto-u.com
#3
Hi all experts, need some advise on focusing please. I am using Nikkor 35mm f1.8 DX. When I tried to take pics with f1.8 using A setting, sometimes I am not able to get a sharp focus on the face for portrait shots after focus and then frame. The sharpness could be on the shoulder or chest area instead. I set my camera to AF-S and I press half shutter and hold and do framing. Could it be that the shutter speed is too slow? Please help. Thank you.
Why Focus-Recompose Sucks
 

#4
We can't see the photo, and have no idea of what settings were used, and we also do not know what AF point(s) were selected.

Lets take a wild guess - either you were too close and beyond the lens' MFD, or the camera's AF points picked-up and locked on a brighter/more contrasty part of the frame.
I am using D90. I have set the focus selector lock to 'L'. My focus point is always in the centre. Let's say for e.g. I taking a pic using the 1/3 rule with the person now on the left side of the 1/3. Initially I focus the focus point on the face while the focus point is in the centre. Then I half shutter to lock focus. And while the half shutter, I do a framing to the 1/3 on the left. Sometimes the face will not be sharp from the results. I am trying to find a pic but could not get one with a gd example. Thanks.
 

#5
The article is great. Thanks. So I should not be setting the focus point to be in the center, rather still adjust the focus point according to where the head of the subject is at since the error tolerance of big aperture is so little?
 

Dream Merchant

Moderator
Staff member
Jan 11, 2007
9,660
6
38
#6
Select the correct AF point that corresponds to the part of the frame you want to focus on.
 

heshanj

New Member
Aug 18, 2009
744
0
0
30
Ho Chi Minh City
pixelogist.me
#8
i also read another article (cant remember where, sorry) which disagreed with the article linked here, and said that the focus/recompose technique works like 99% of the time, and needs drastic conditions for u to get an out of focus image. it was a pretty reputable site i read this on (i think bob atkins). so im not sure wat to believe. i generally focus/recompose, and my images are pretty well in focus, but im not sure. maybe i should start changing AF points and focusing like that more
 

HLZQ4

New Member
Jun 27, 2008
145
0
0
Sg
#10
If you are Using a big aperture it is possible to get out of focus after u recompose as a slightly different plane will cause oof at big apertures. If your cam allows the focus and exposure buttons to be separated it might solve the problem
also, have u ruled out the possibility that your lens has back focus issues?
 

#11
See attached article.

At the end of the day ... use whichever technique works for you. Don't need to care who write what agree lah disagree lah - it's your camera, your photos. :)
I read alrady.. but I dunno why my focus/recompose will be blur leh. :dunno:
 

night86mare

Deregistered
Aug 25, 2006
25,541
0
0
www.pbase.com
#12
Hi all experts, need some advise on focusing please. I am using Nikkor 35mm f1.8 DX. When I tried to take pics with f1.8 using A setting, sometimes I am not able to get a sharp focus on the face for portrait shots after focus and then frame. The sharpness could be on the shoulder or chest area instead. I set my camera to AF-S and I press half shutter and hold and do framing. Could it be that the shutter speed is too slow? Please help. Thank you.
what sort of shutter speeds?

the dof is not exactly going to be very deep, you should take out of that, if your recomposition causes an over-drastic change, better to use select af point.
 

#13
what sort of shutter speeds?

the dof is not exactly going to be very deep, you should take out of that, if your recomposition causes an over-drastic change, better to use select af point.
I am using Aperture priority setting. According to the raw image, it is 1/60s. The distance was never changed when I do a focus/framing. I am using AF-S and the D90 focus was 'L' at the back of D90 and lock the focus point in the centre. Is this the right way to do focus/framing?
 

Dream Merchant

Moderator
Staff member
Jan 11, 2007
9,660
6
38
#14
I read alrady.. but I dunno why my focus/recompose will be blur leh. :dunno:
It's called parallelax error.

http://en.wikipedia.org/wiki/Parallax

1/60 for a 35mm lens, crop factor or not, should be easily hand-holdable.

Simple answer is learn to select the af point closest to the part of the frame you want in focus.
 

Last edited:

night86mare

Deregistered
Aug 25, 2006
25,541
0
0
www.pbase.com
#18
I am using Aperture priority setting. According to the raw image, it is 1/60s. The distance was never changed when I do a focus/framing. I am using AF-S and the D90 focus was 'L' at the back of D90 and lock the focus point in the centre. Is this the right way to do focus/framing?
unless you are having parkinson's, there should be no reason for handshake at 1/60 second for 35mm focal length.

distance never change, but like others mentioned, you have to be aware how dof works, it 's like taking a slice out of reality. i.e. what you want in focus lies between x distance and y distance from your camera, parallel to sensor.

when you recompose, your plane changes, so the slice becomes different and what you wanted in focus is now on another plane.
 

daredevil123

Moderator
Staff member
Oct 25, 2005
21,645
63
48
lil red dot
#20
I read alrady.. but I dunno why my focus/recompose will be blur leh. :dunno:
I am using Aperture priority setting. According to the raw image, it is 1/60s. The distance was never changed when I do a focus/framing. I am using AF-S and the D90 focus was 'L' at the back of D90 and lock the focus point in the centre. Is this the right way to do focus/framing?
Yup, I have read that multiple times. With my kit lens, no problem. But with 35mm f1.8, the face will not be sharp. Strange.
If even after reading the article, you still have no clue why your shots are still blur when doing focus and recompose, maybe you should give up the hobby all together. Really.
 

Top Bottom