Is this shallow DOF or something else?

Snapper

Not sure if this is the right forum for the question but perhaps the moderators would be kind enough to move it if necessary.

I'm just easing into the wonderful world of DSLR photography after many years of point-and-shoot. I do have a basic knowledge of aperture/shutter speed/film speed corelation etc.

The linked photo was shot on a Nikon D80 with the 35-135 zoom set at 50mm, 125th at f5, ISO400, and SB800 iTTL/BL on the hot shoe.

The child on the left is out of focus. She is very slightly in front of the other two kids, but I would have thought an aperture of f5 focussed on the eyes of the centre child would have brought all the children into focus.

I've noticed it in a few group shots, always with the person on the left, so just wanted to confirm that this is indeed DOF and not something wrong with the new camera!

http://www.igmusic.co.nz/epix/20070603_0290.jpg

Thanks in advance.

luke_church

Snapper wrote:

The child on the left is out of focus. She is very slightly in front of the other two kids, but I would have thought an aperture of f5 focussed on the eyes of the centre child would have brought all the children into focus.

Looks like a DOF issue.

-> Your camera is a 1.5 crop (am I right?), so that pushes the effective focal length

-> The photo looks as if you were fairly close to the girls, that means that you'll get a shallow DOF

-> It looks as if the centre girl's eyes are pretty near the front of the 'infocus cuboid' (c.f. observe that her hair on the top of her head is pretty much all in focus)

-> You can just about see the sharp bit ending on the girl to the left's hair. If it ends there, then yeah, the face is going to be very soft...

So I doubt it's a problem. If you're really worried, get a nice patterned brick wall, and take a photo making sure that the focal plane is parralel to the wall (i.e. face on to the wall).

I would suspect that this is normal :-)

HTH,

Luke

Snapper

luke_church wrote:

Looks like a DOF issue.

-> The photo looks as if you were fairly close to the girls, that means that you'll get a shallow DOF

-> It looks as if the centre girl's eyes are pretty near the front of the 'infocus cuboid' (c.f. observe that her hair on the top of her head is pretty much all in focus)

-> You can just about see the sharp bit ending on the girl to the left's hair. If it ends there, then yeah, the face is going to be very soft...
Luke

Thanks Luke. I suspect I moved slightly closer after I'd set the focus.

Stu Engelman

Hi Snapper,

I suspect you made this shot very close to the girls, resulting in a very narrow DOF around them. The wide aperture likely made the problem worse. Moving farther from your the subjects, and stopping down your aperture (say to F11), will greatly increase your DOF. The choice of a 50mm moderate telephoto was good here (not too much pinch or bloat in the image). At a farther distance, you might need to zoom to 75mm say, but this is also a good lens for portraits (will be a little flatter in prespective, but still will look good).

I downloaded your image and did some post-processing in Photoshop. First, I ran the Reduce Noise filter (at 50% strength to avoid overly softening the image) to partially eliminate the high ISO artifacts (luminance dots in the dark areas). This was preparatory to sharpening the left hand girl, as I did not want to sharpen the noise. I then drew a freehand lasso around the fuzzy portion of the left hand girl, feathered the selection by 10 pixels, masked a copy of the image, and ran Smart Sharpen at 1.5/150. Finally, with a soft round brush, I subtracted from the mask where remaining luminance noise was being sharpened, and then did a little spotting with the Spot Healing Brush and Patch Tool. The revised image is uploaded with this post (reduced in size due to SmugMug file size limit). The high ISO setting makes it impossible to get the left hand girl as sharp as the others (too much noise sharpening would go with it), but it is an improvement.

In general, try to avoid ISO's over 200 or so unless absolutely necessary. You can't post-process the artifacts out without blurring the image.

Just let me know if you'd like the Photoshop file and I'll figure out a way to get it to you.

Best regards, Stu

Snapper

Stu Engelman wrote:

Hi Snapper,

I suspect you made this shot very close to the girls, resulting in a very narrow DOF around them. The wide aperture likely made the problem worse. Moving farther from your the subjects, and stopping down your aperture (say to F11), will greatly increase your DOF. The choice of a 50mm moderate telephoto was good here (not too much pinch or bloat in the image). At a farther distance, you might need to zoom to 75mm say, but this is also a good lens for portraits (will be a little flatter in prespective, but still will look good).

I downloaded your image and did some post-processing in Photoshop. First, I ran the Reduce Noise filter (at 50% strength to avoid overly softening the image) to partially eliminate the high ISO artifacts (luminance dots in the dark areas). This was preparatory to sharpening the left hand girl, as I did not want to sharpen the noise. I then drew a freehand lasso around the fuzzy portion of the left hand girl, feathered the selection by 10 pixels, masked a copy of the image, and ran Smart Sharpen at 1.5/150. Finally, with a soft round brush, I subtracted from the mask where remaining luminance noise was being sharpened, and then did a little spotting with the Spot Healing Brush and Patch Tool. The revised image is uploaded with this post (reduced in size due to SmugMug file size limit). The high ISO setting makes it impossible to get the left hand girl as sharp as the others (too much noise sharpening would go with it), but it is an improvement.

In general, try to avoid ISO's over 200 or so unless absolutely necessary. You can't post-process the artifacts out without blurring the image.

Just let me know if you'd like the Photoshop file and I'll figure out a way to get it to you.

Best regards, Stu

Wow! Thanks Stu. The smart sharpening works wonders. Unfortunately I'm still running PS CS so don't have that filter. Thanks for taking the time to look at this.

--Ian