How should I correct this mistake

lensego · 06-30-2010, 09:17 AM

Name: AF problem.jpg
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Hi guys. What em I doing wrong? I'm getting at least 30% of my pics like that:
Center of the picture is not sharp . I used Fa 50/1.4 at wide open. I'm loosing lots of pics that way. I understand the DOF is very short at 1.4, but why is that lens focusing behind my little beautiful sobject? Lots of funny sad etc faces are gone by that mistake

ps: If it is not obvious :the face is out of focus, but the jumper around the neck is sharp.
Any help would be great
regards zoltan

graphicgr8s · 06-30-2010, 09:29 AM

Not enough information. Are you autofocusing? If so where is your focus point? Are you getting focus then recomposing?

Try an experiment. Try focusing manually. See if it works.

Also what camera?

JeffJS · 06-30-2010, 09:32 AM

Do you have a camera that you can adjust the AF on (K20d, K7)?

Short of that, put the switch on the camera to MF and try that. You might also stop the lens down a little bit to say, f2. Still leaves plenty of blur in the background and negates the razor thin DOF on your subject.

cloudphreak · 06-30-2010, 09:38 AM

Shooting the 50mm wide open at 1.4, from roughly 4 ft away (my estimate) gives a DOF of less than 1.5 inches. Try setting the AF point to center focus only, then recompose. You'll still probably have to stop down some.

Ben_Edict · 06-30-2010, 10:05 AM

Originally posted by lensego

Attachment 65314
Hi guys. What em I doing wrong? I'm getting at least 30% of my pics like that:
Center of the picture is not sharp . I used Fa 50/1.4 at wide open. I'm loosing lots of pics that way. I understand the DOF is very short at 1.4, but why is that lens focusing behind my little beautiful sobject? Lots of funny sad etc faces are gone by that mistake

ps: If it is not obvious :the face is out of focus, but the jumper around the neck is sharp.
Any help would be great
regards zoltan

Hi Zoltan, in a portrait you want to get the eyes sharp. How would the camera know that? Your image does not contain exif data, so I can only guess what may be the reason and you need to give more technical details!

1. You might have set auto AF point selection. In that case the camera probably choose the nearestz point as being the most important (again: how could a camera know otherwise). The shoulder is nicely focused. OR

2. you set the AF center point fixed. Then again the eyes are not in the center of the image and its is a necessary result, that the image is misfocused.

By the way, the camera does not focus "behind your little beauty", but in front - at least in the example image.

Ben

Marc Sabatella · 06-30-2010, 10:12 AM

This is why it's often observed that f/1.4 is ovdrkill and counterproductive much of the time - DOF is simply too small. Even the slightest movement on your part or the subject's part changes the focus - and that's assuming you carefully chose and positioned the focus point in the first place, which it isn't clear if you did. Looks like a little motion blur in the head too - based on the position of the focs on the collar, I'd have otherwise expected the eyes to be sharper than that.

dragonfly · 06-30-2010, 10:12 AM

A light source might help.

MSM · 06-30-2010, 11:30 AM - **1 Like**

Also, if you are using the center point and recomposing, make sure that you are shooting AF-S and not AF-C. Otherwise, as you lock on the eyes with the AF, the camera will refocus as you recompose.

bigdog104 · 06-30-2010, 11:35 AM

Originally posted by Marc Sabatella

This is why it's often observed that f/1.4 is ovdrkill and counterproductive much of the time - DOF is simply too small. Even the slightest movement on your part or the subject's part changes the focus - and that's assuming you carefully chose and positioned the focus point in the first place, which it isn't clear if you did. Looks like a little motion blur in the head too - based on the position of the focs on the collar, I'd have otherwise expected the eyes to be sharper than that.

To echo what others have been saying, with any lens, the "sweetspot" exists about 2 f stops above the maximum, so the best way to use a 50mm F1.4 is to limit yourself to f2 to f2.8.

Ben_Edict · 06-30-2010, 12:11 PM

Originally posted by bigdog104

To echo what others have been saying, with any lens, the "sweetspot" exists about 2 f stops above the maximum, so the best way to use a 50mm F1.4 is to limit yourself to f2 to f2.8.

A portrait shot (or any other photograph) is not about using the maximum sharpness of a lens, but about achieving a certain visual goal. Therefor using f/1.4 has its own uses and merrits.
Especially for portraits the increased aberrations and the slight loss of contrast can produce very flattering and desirable results.

One should only "generally" do something, if one is prepared to deviate from these "general" rules, to achieve something else.

I would also emphasize, that with this particular image the real problem is not the f-stop, but the general misfocus.

Ben

HEEGZ · 06-30-2010, 01:30 PM

Originally posted by bigdog104

To echo what others have been saying, with any lens, the "sweetspot" exists about 2 f stops above the maximum, so the best way to use a 50mm F1.4 is to limit yourself to f2 to f2.8.

This is the first thing I would try.

Andi Lo · 06-30-2010, 02:23 PM

What's the shutter speed?

KxBlaze · 06-30-2010, 03:25 PM - **1 Like**

You may have a back focusing issue and that can be corrected on a K20 or K7 for individual lenses and on the Kx it can be done but it will correct it for all lenses across the board.

If back focus is not the issue than it could be that there is no problem at all because like you said 1.4 has a very small DOF and the few centemeters from the eyes to the shirt collar can make a focusing difference.

To see if it's a back focusing issue you can do the batter test. Set up 3 batteries in a diagonal line, just a few centemeters apart and focus on the middle battery and see if you pictures come out focused anywhere else other than the middle battery (make sure you do the test at 1.4).

hcc · 06-30-2010, 06:19 PM

You already received a lot of useful comments.

For me the photo seems slightly out of focus. A recent post pointed to the software Focus Magic (Recover Detail and Sharpen Your Blurred Photos) that helps to PP a photo that is out of focus:
https://www.pentaxforums.com/forums/digital-processing-software-printing/1006...bad-photo.html

It might help if you cannot take another shot, but it would be best to improve the photo technique.

Another suggestion is to use a 100 mm instead of 50mm to take the portrait shot, and, as pointed by Marc, to use a smaller aperture (larger f).

aleonx3 · 06-30-2010, 06:33 PM

As many have already pointed out, it could be a number of factors.
-DOF too shallow (on part of face which is hard to be accurate - lack of contrast)
-a bit too close to subject (hence much shallower DOF)
-shutter speed could be a tad too slow
-subject movement (due to slow shutter speed)
-BF issue on this lens (which can be corrected)

I often try:
-more DOF to work with
-use center point (spot with more contrast)
-stead the camera
-higher shutter speed to compensate for slight movement of camera/subject
-if the problem still exists, try BF adjustment
-try different lens

Anyway, have fun...

06-30-2010, 09:17 AM	#1
lensego Forum Member Join Date: May 2010 Location: PERTH Photos: Gallery \| Albums Posts: 50	How should I correct this mistake Hi guys. What em I doing wrong? I'm getting at least 30% of my pics like that: Center of the picture is not sharp . I used Fa 50/1.4 at wide open. I'm loosing lots of pics that way. I understand the DOF is very short at 1.4, but why is that lens focusing behind my little beautiful sobject? Lots of funny sad etc faces are gone by that mistake ps: If it is not obvious :the face is out of focus, but the jumper around the neck is sharp. Any help would be great regards zoltan

06-30-2010, 06:19 PM	#14
hcc Pentaxian Join Date: Nov 2009 Location: Brisbane, Australia Photos: Gallery \| Albums Posts: 4,004	You already received a lot of useful comments. For me the photo seems slightly out of focus. A recent post pointed to the software Focus Magic (Recover Detail and Sharpen Your Blurred Photos) that helps to PP a photo that is out of focus: https://www.pentaxforums.com/forums/digital-processing-software-printing/1006...bad-photo.html It might help if you cannot take another shot, but it would be best to improve the photo technique. Another suggestion is to use a 100 mm instead of 50mm to take the portrait shot, and, as pointed by Marc, to use a smaller aperture (larger f). Last edited by hcc; 06-30-2010 at 06:21 PM. Reason: Typos

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06-30-2010, 09:29 AM	#2
graphicgr8s Guest	Not enough information. Are you autofocusing? If so where is your focus point? Are you getting focus then recomposing? Try an experiment. Try focusing manually. See if it works. Also what camera?

06-30-2010, 09:32 AM	#3
JeffJS Inactive Account Join Date: Aug 2008 Location: Michigan, USA Photos: Gallery \| Albums Posts: 7,484	Do you have a camera that you can adjust the AF on (K20d, K7)? Short of that, put the switch on the camera to MF and try that. You might also stop the lens down a little bit to say, f2. Still leaves plenty of blur in the background and negates the razor thin DOF on your subject.

06-30-2010, 09:38 AM	#4
cloudphreak Junior Member Join Date: May 2010 Location: Ashburn, VA Photos: Albums Posts: 30	Shooting the 50mm wide open at 1.4, from roughly 4 ft away (my estimate) gives a DOF of less than 1.5 inches. Try setting the AF point to center focus only, then recompose. You'll still probably have to stop down some.

06-30-2010, 10:05 AM	#5
Ben_Edict Veteran Member Join Date: Jul 2007 Location: SouthWest "Regio" Photos: Albums Posts: 3,309	Originally posted by lensego Attachment 65314 Hi guys. What em I doing wrong? I'm getting at least 30% of my pics like that: Center of the picture is not sharp . I used Fa 50/1.4 at wide open. I'm loosing lots of pics that way. I understand the DOF is very short at 1.4, but why is that lens focusing behind my little beautiful sobject? Lots of funny sad etc faces are gone by that mistake ps: If it is not obvious :the face is out of focus, but the jumper around the neck is sharp. Any help would be great regards zoltan Hi Zoltan, in a portrait you want to get the eyes sharp. How would the camera know that? Your image does not contain exif data, so I can only guess what may be the reason and you need to give more technical details! 1. You might have set auto AF point selection. In that case the camera probably choose the nearestz point as being the most important (again: how could a camera know otherwise). The shoulder is nicely focused. OR 2. you set the AF center point fixed. Then again the eyes are not in the center of the image and its is a necessary result, that the image is misfocused. By the way, the camera does not focus "behind your little beauty", but in front - at least in the example image. Ben

06-30-2010, 10:12 AM	#6
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	This is why it's often observed that f/1.4 is ovdrkill and counterproductive much of the time - DOF is simply too small. Even the slightest movement on your part or the subject's part changes the focus - and that's assuming you carefully chose and positioned the focus point in the first place, which it isn't clear if you did. Looks like a little motion blur in the head too - based on the position of the focs on the collar, I'd have otherwise expected the eyes to be sharper than that.

06-30-2010, 10:12 AM	#7
dragonfly Veteran Member Join Date: Jun 2009 Location: on the wall Photos: Gallery Posts: 715	A light source might help.

06-30-2010, 11:30 AM - 1 Like	#8
MSM Veteran Member Join Date: Dec 2007 Location: Alabama Photos: Gallery Posts: 994	Also, if you are using the center point and recomposing, make sure that you are shooting AF-S and not AF-C. Otherwise, as you lock on the eyes with the AF, the camera will refocus as you recompose.

06-30-2010, 11:35 AM	#9
bigdog104 Senior Member Join Date: Apr 2010 Location: South Carolina Photos: Gallery Posts: 289	Originally posted by Marc Sabatella This is why it's often observed that f/1.4 is ovdrkill and counterproductive much of the time - DOF is simply too small. Even the slightest movement on your part or the subject's part changes the focus - and that's assuming you carefully chose and positioned the focus point in the first place, which it isn't clear if you did. Looks like a little motion blur in the head too - based on the position of the focs on the collar, I'd have otherwise expected the eyes to be sharper than that. To echo what others have been saying, with any lens, the "sweetspot" exists about 2 f stops above the maximum, so the best way to use a 50mm F1.4 is to limit yourself to f2 to f2.8.

06-30-2010, 12:11 PM	#10
Ben_Edict Veteran Member Join Date: Jul 2007 Location: SouthWest "Regio" Photos: Albums Posts: 3,309	Originally posted by bigdog104 To echo what others have been saying, with any lens, the "sweetspot" exists about 2 f stops above the maximum, so the best way to use a 50mm F1.4 is to limit yourself to f2 to f2.8. A portrait shot (or any other photograph) is not about using the maximum sharpness of a lens, but about achieving a certain visual goal. Therefor using f/1.4 has its own uses and merrits. Especially for portraits the increased aberrations and the slight loss of contrast can produce very flattering and desirable results. One should only "generally" do something, if one is prepared to deviate from these "general" rules, to achieve something else. I would also emphasize, that with this particular image the real problem is not the f-stop, but the general misfocus. Ben

06-30-2010, 01:30 PM	#11
HEEGZ Senior Member Join Date: Jun 2010 Location: Missouri Photos: Albums Posts: 258	Originally posted by bigdog104 To echo what others have been saying, with any lens, the "sweetspot" exists about 2 f stops above the maximum, so the best way to use a 50mm F1.4 is to limit yourself to f2 to f2.8. This is the first thing I would try.

06-30-2010, 02:23 PM	#12
Andi Lo Veteran Member Join Date: Jul 2008 Location: Halifax, Nova Scotia Posts: 2,924	What's the shutter speed?

06-30-2010, 03:25 PM - 1 Like	#13
KxBlaze Veteran Member Join Date: Feb 2010 Location: California Photos: Gallery Posts: 1,602	You may have a back focusing issue and that can be corrected on a K20 or K7 for individual lenses and on the Kx it can be done but it will correct it for all lenses across the board. If back focus is not the issue than it could be that there is no problem at all because like you said 1.4 has a very small DOF and the few centemeters from the eyes to the shirt collar can make a focusing difference. To see if it's a back focusing issue you can do the batter test. Set up 3 batteries in a diagonal line, just a few centemeters apart and focus on the middle battery and see if you pictures come out focused anywhere else other than the middle battery (make sure you do the test at 1.4).

06-30-2010, 06:33 PM	#15
aleonx3 Veteran Member Join Date: Jul 2007 Location: Brampton, Ontario Photos: Gallery \| Albums Posts: 3,996	As many have already pointed out, it could be a number of factors. -DOF too shallow (on part of face which is hard to be accurate - lack of contrast) -a bit too close to subject (hence much shallower DOF) -shutter speed could be a tad too slow -subject movement (due to slow shutter speed) -BF issue on this lens (which can be corrected) I often try: -more DOF to work with -use center point (spot with more contrast) -stead the camera -higher shutter speed to compensate for slight movement of camera/subject -if the problem still exists, try BF adjustment -try different lens Anyway, have fun...