need HELP improving sharpness in macro studio situation

[FishMan473]

I'm an ecologist, and right now I'm working on cleaning and stratifying seeds so I can plant them in the spring. I have decided I would like to take pictures of all of the seeds so I can use these photos to help identify seeds in the future.

So I set up a little "macro studio" on the work table in my office. I have my D300s with my Nikon AF Micro Nikkor 60mm f/2.8D lens on a tripod, with the lens as parallel to the table surface as I can get it. For lighting I am using the built in flash along side a high powered (960 lumen) LED light. I have manually set the white balance, ISO set at 200, and am shooting at the full 12 MP, trying out both JPEG and RAW (though I kind of prefer the smaller file size for this project). Shooting in Mirror-Up mode with a wired remote in Aperture Priority mode at F22 and getting about 1/90th shutter speed (I am also playing with stopping down the lens even further since I have plenty of light). Auto focus.

So, with all that said, I am not getting the sharpness I am hoping for with these images. A lot of these seeds have some fine texture to them and somehow I am not getting it. It doesn't look like motion blur, it seems to be some other sort of distortion. Frankly, I think I've gotten more detail hand holding outside on a sunny day, so I don't think this is a limitation of my lens, but I might be wrong. Am I just asking too much of my equipment?

Here are some example shots, cropped down to the fine details:

http://picasaweb.google.com/frank.hassler/Seeds?feat=directlink

[BlueRob]

I´m not familiar with Nikon but seems that what is wrong is the focus.
I might suggest to decrease the f number as possible to shorten the shutter speed, try manual focus or maybe move the camera back, it might be to close to acquire good AF.

What other lenses do yo have?....again without knowing that particular lens it seems to be too "big" (60mm) for macro. Is you camera set in Macro mode? this will aid no doubt.

[freygr]

Remember you have to pay attention to the aperture of the lens with close up photography (Micro-photography) You need the aperture to up there to the get largest DOF you can get with still life micro-photography. There are online DOF calculators.

[FishMan473]

BlueRob: The focus is well within the range of this lens, well, I could get maybe another cm closer. I just tried manual focus and the results are similar. This could still be part of the problem, I don't really trust my eye to focus correctly.

freygr: I figure F22 should give me a workable depth of field....

OK, just tried this DOF calculator (http://www.dofmaster.com/dofjs.html) and its telling me I have a .5 mm DOF. Not much to work with, but the seeds in the above picture are probably .3 mm thick (they are about .5 mm long). So unless something is wrong with my autofocus I should still get something. I think I will start by moving the camera up a bit to give me a bit more working distance and more DOF. So far stopping down the aperture further hasn't done much, but I'll give it another try. OTOH, could distortion due to the high f-stop be causing a problem too?

[BlueRob]

Yes I think F could cause the problem too. Try using the camera on auto Auto (macro) see if the results are better if yes check the Exif to see the parameters to have a "starting point" for shooting manual mode.

[SmartWombat]

I think DSC_6446 shows the very small depth of field clearly.
Follow the curve of the "tail" on that left hand seed, as it gets closer to the background it gets closer to in-focus. The body of the seed itself is not in focus, the focus is nearer the background.

.again without knowing that particular lens it seems to be too "big" (60mm) for macro

It is a macro lens. It's specialised for that job.

You need the aperture to up there to the get largest DOF you can get

Not necessarily. At some point you close the aperture too far and you get diffraction softening the image.
So it is best to try a range of apertures to see where it appears sharpest.
Every lens is different, so trying to give a specific aperture won't help much.
Just take notes !

[SmartWombat]

I have a .5 mm DOF. Not much to work with, but the seeds in the above picture are probably .3 mm thick (they are about .5 mm long).

Have you missed a decimal point?
I would have thought the seeds were 3mm by 5mm.
On that scale the DoF looks like about 0.5mm

[FishMan473]

No those are some tiny, tiny seeds. The tan ones are anyway, .5mm long, might only be .2 thick. There are two different species in the example shots, the one with the spiraling seed pod and odd shaped dark brown seeds are closer to 3 mm long, with the seed pods being over 1 cm long.

Not totally sure on that larger second species because my cat has played with this set up over night and scattered the only couple of that species I had. Paul, I see you have a tortie cat in your avitar, so I'm sure you understand.

[Loupey]

Two suggestions:

1) You are seeing the effects of diffraction so try f/8 and f/11 and that should improve resolution - at the cost of DOF of course

2) Avoid the built in flash at all costs. Even if you have to use simple table lighting from multiple sources and exposures in the several seconds range, the results should be better.