Is my 18-200 frontfocusing?

<p>I have had some difficulties taking the sharp photos with the Nikon 18-200mm +D300. The image just isnt sharp enough. Does it look like a frontfocusing problem? From the pics below looks like the grass in front of kids is much sharper than where the focus point is. Did anybody else have the same problem?<br /> <img src="http://i84.photobucket.com/albums/k28/alfaromeo155/ff.jpg" alt="" width="1008" height="704" /> <img src="http://i84.photobucket.com/albums/k28/alfaromeo155/fff.jpg" alt="" width="423" height="1023" /></p>

<p>The best way to check is using one of the focus test guides and conduct a controlled test such as the one below: http://focustestchart.com/chart.html</p>

<p>hard to tell with grass. it might have to do with the amount of reflective light which falls on the grass. it looks more to me like the background is nicely out of focus than an obvious case of FF. you could try again with another, more contrastier scene. we also dont know what settings you used on your camera and body. the 18-200 is not noted for its ginsu-like sharpness,so that might be about what you can expect from that lens without really tweaking aperture and/or metering/focus settings.<br>

but that pic looks fine to me, other than the fact that there's too much green space--your crop should have been the original shot. next time focus a bit tighter on your main subjects, if you dont have a compelling background.</p>

 

<p>Was noise reduction in play, here? Look at the well-exposed areas of her hair (top left), which is showing some detail. The faces, which are in shadow, may have been softened a bit by in-camera or post noise reduction. The grass in front doesn't look particularly sharper to me than the faces - it's just contrastier, so it gives that appearance.</p>

<p>If you look only at the grass, it certainly appears that the grass closest to the bottom edge is sharper than the grass further out.<br>

Jerry, post a 100% crop of a vertical slice of grass, from the bottom edge, up towards the center 600 pixels.</p>

<p>Need to know more about how you shot that. If the focus area was automatically selected, maybe it wasn't focusing where you wanted it.</p>

<p>That said, that photo doesn't look so bad to me! How much were the kids moving is another question.</p>

<p>I will do a more controlled experiment with the test chart, but this is what I have been getting almost all the time. Kids werent really moving around, the focus point was the center one, wasnt automatically selected</p>

<p>F/stop, Jerry?</p>

<p>shooting test chart reveals nothing, looks like it is OK where it should be, but the pictures look frontfocused. Could this be a VR related? I've noticed when shooting the chart with VR on the focus point slightly changes after the shutter was released, it moves to the front<br /> <img src="http://i84.photobucket.com/albums/k28/alfaromeo155/DSC_0334.jpg" alt="" /> <img src="http://i84.photobucket.com/albums/k28/alfaromeo155/DSC_0311.jpg" alt="" /></p>

<p>The grass at the boy's foot is already blurry,while it's clear 1 foot in front of his knee. I wonder if AF picked up his right hand, and focused on that? Even though it's motion-blurred in this pic...</p>

<p>i think the grassy areas seeming to be 'sharper' is an optical illusion caused by the reflected light on the grass. the areas in both pics where there is no reflected light dont seem any sharper. the last example clearly shows the gass next to the kneee to be about as sharp as the grass one foot in front of him. if you were to crop out a patch of grass with no reflected light from both areas, i think you'd find them to be about equal sharpness. in that last pic, the grass in front of the kid doesn't seem any sharper than his face, although comparing skin tones to nature tones perhaps isnt the best comparison.</p>

<p>also, jerry, we still don't know your settings, but as i said before, the 18-200 isnt the sharpest lens out there. it generally needs to be at f/8-f/11 to produce results which don't show some softness. the OoF areas in the background suggest maybe you were at a wider aperture? given that, if the 18-200 isn't crisp enough for you on a d300, it may be time to invest in a new piece of glass. the 50/1.8 or 35/1.8 should improve on the sharpness factor and are both relatively inexpensive.</p>

<p>eric, it was f5.6 the max you can get at 200mm with this lens, and about 1/1000s shutter speed, I wanted to achieve shallow DOF</p>

<p>well, that kind of explains it. for a wide-open pic with that lens at that focal length, i dont think your results are atypical at all. if you want shallow DoF and sharpness, you'll need a faster lens, i'm afraid.</p>

<p>I concur that the lens is shaper at f/8 than f/5.6, which is why I asked what your f/stop was. However, my own, somewhat informal tests show me that my lens is soft at 5.6, but only on the edges, but not particularly in the center of the image. Make some tests at different f/stops, and keep away from f/5.6 when you can (or 3.5 at the wide end).</p>

<p>yes, I agree with 5.6 being soft, but not in the center , it shouldnt matter for the center whether it is 5.6 or 8-11</p>

<p>The 18-200 is not the sharpest lens wide open, especially longer than 100. All the reviews say this, and my experience with this lens bears it out. </p>

<p>You write "Yes, I agree with 5.6 being soft, but not in the center , it shouldnt matter for the center whether it is 5.6 or 8-11". Incorrect. This lens is not super sharp at the long end wide-open... If you need more sharpness at f5.6, you have the wrong lens.<br>

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The last crop you showed displays what I would expect with this lens. And I think it's fine, just how big are you going to print anyway? I bet this image would just fine on an 8 x 10.</p>