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Old Oct 22, 2009, 1:08 AM   #1
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Default Macro Focusing Problems with the D90

Hi,

I recently switched from the D70 to the D90, shooting macro with a copy stand and a Sigma 180mm macro lens. I've been having some trouble getting really sharp photos with the D90, a problem I never had with the D70.

With the D70, I was usually shooting with AF-C/Single area autofocus. My main subjects are coins, and it's important that all depths be in focus, such as in this shot, taken with the D70: http://jkwd.com/coins/coins/dollar/m...001_obv-sm.jpg

With the D90, I've tried playing with the autofocus and manual focus, and can't get it quite right... there's just a hint of softness in the shot, even when it looks extremely crisp in the viewfinder. I moved up to a sturdier copy stand than I used to use (now using this: http://www.adorama.com/CECS920.html) and I use a remote to minimize shaking.

While the problem is obviously more noticeable at full resolution, it can still appear without some sharpening when images are scaled down.

If anyone has any suggestions for either manually focusing or autofocus (I think I've tried all the settings by now), I'd really appreciate it. I'm also pretty sure that the diopter is in focus, but it's to the point where I can hardly tell the difference between a few of the settings.

Thanks,

Jeremy
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Old Oct 22, 2009, 6:20 AM   #2
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Do you have another lens you can try it with?

The reason I ask is because your D70 had a resolution of 6MP, while the D90 is 12MP. It could just be that the greater resolution makes any possible softness of the lens more visible.

And do you still have the D70?
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Old Oct 23, 2009, 12:44 AM   #3
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I do still have the D70 and will try to get some comparison shots soon. That said, it's not just slightly soft--many shots just come out a tad, but noticeably, out of focus. It's also good glass, and quite a sharp lens among others whom I know use it.
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Old Oct 23, 2009, 1:37 AM   #4
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Yes. I was hesitant to suggest it, because the Sigma 180/3.5 has such a good track record. Since the lens works well on one camera but not another, it's easy to pin it on the camera, but just to be sure, I suggest that you see if you get similar results with a different lens. It's a fast, simple way to confirm the source of the problem without spending any money.
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Old Oct 23, 2009, 1:23 PM   #5
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That's a good idea... I'll plug in my Sigma 105mm macro and see how it fairs.
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Old Oct 23, 2009, 1:25 PM   #6
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I should also point out that I did some tests with plain text, as well. The autofocus was decent (not totally crisp) and manual was soft even when it was extremely sharp in the viewfinder.
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Old Oct 23, 2009, 2:38 PM   #7
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Quote:
Originally Posted by airplanenut View Post
I should also point out that I did some tests with plain text, as well. The autofocus was decent (not totally crisp) and manual was soft even when it was extremely sharp in the viewfinder.
That sounds like Front Focus/Back Focus. You might also try http://www.focustestchart.com/chart.html. It talks from the perspective of a D70, but what it has to say is universal. Do the test, and see what happens.
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Old Oct 23, 2009, 3:16 PM   #8
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Thanks... if it is a focusing issue, is there an easier step to fixing it other than calling up Nikon?
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Old Oct 23, 2009, 9:51 PM   #9
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I don't know of one. The D90 doesn't have the microadjust feature that the D300 has.
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Old Oct 24, 2009, 8:18 AM   #10
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You may just be seeing differences in the camera output (unrelated to focus accuracy). I'd check for AF problems (as TCav suggested) to find out. But, if you look at some of the D90 reviews, I think you'll find that it's got slightly lower "per pixel" sharpness compared to some cameras (even compared to the D300 when shooting in either JPEG or RAW, even though both use a similar 12MP Sony Sensor). For example, note the comments about it's output being "very soft" on the bottom of this page in it's dpreview.com review:

http://www.dpreview.com/reviews/NikonD90/page27.asp

Or, on this page comparing the D90 JPEG output to the D300 JPEG output:

http://www.dpreview.com/reviews/NikonD90/page29.asp

Or, see the comments at the bottom of this page, comparing the D90 RAW output to the D300 RAW output using ACR for conversions:

http://www.dpreview.com/reviews/NikonD90/page33.asp

My best guess is that Nikon is using a stronger AA filter with the D90, hence the softer output, even when shooting RAW (but, it could be related to pre-processing that Nikon does with RAW files from the D90, too).

Also, keep in mind that your D70 has a very weak AA filter (hence, it has a reputation for great "per pixel" sharpness). But, on the downside, it's more prone to Moiré

You'll find some discussion of that issue with the D70 in it's review conclusion here at Steve's.

http://www.steves-digicams.com/camer...-review-8.html

You'll also see some samples of the problem at the bottom of it's review samples page:

http://www.steves-digicams.com/camer...review-10.html

IOW, there are pros and cons to a weaker AA filter, as Nikon used with the D70. ;-)

So, you may need to use a bit of USM in post processing (depending on the desired viewing/print sizes) to get sharpness similar to a D70.

But, despite differences in AA filter designs, processing, etc., you should be able to capture a lot more "real" detail with the D90 (which should look nice at a given print/viewing size when compared to the lower resolution D70's output, once sharpened a bit).
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