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06-30-2010, 09:17 AM   #1
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How should I correct this mistake

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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

06-30-2010, 09:29 AM   #2
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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
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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
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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
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QuoteOriginally posted by lensego Quote
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
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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
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A light source might help.
06-30-2010, 11:30 AM - 1 Like   #8
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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
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QuoteOriginally posted by Marc Sabatella Quote
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
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QuoteOriginally posted by bigdog104 Quote
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
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QuoteOriginally posted by bigdog104 Quote
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
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What's the shutter speed?
06-30-2010, 03:25 PM - 1 Like   #13
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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, 06:19 PM   #14
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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
06-30-2010, 06:33 PM   #15
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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...
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