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I work in a marijuana testing lab in Washington. Part of our workflow is to capture an image of each sample as it is weighed, for later reference/analysis. We're pretty excited to be creating high quality standardized scientific images tied to a wealth of data, and hope to pass on this value to the public through some creative applications.
The trouble is I'm having difficulty getting sharp enough images with sufficient depth of field (about 2" for most samples) with our Nikon D5000 + Nikkor Micro 40mm lens. We had been using the kit Nikkor lens, but it simply was not sharp enough. We're using Digicam Controller to tether the camera to our lab's web application. To minimize workload, the camera needs to be on autofocus with no parameter adjustment from the technician.
We have a camera enclosure that I built which allows the camera to be moved up or down about a foot, with a minimum distance of about 6 inches to about a foot and a half. Currently, the lens is about 11" away from the muffin cup, which produces a full-frame shot. White balancing will be handled in post-processing, and you can see there is a neutral grey card affixed to the scale for reference.
I imagine that one of the main problems is that we're not getting enough light from the fluorescent lamp in the box, so I'm considering getting an LED ring light to help reduce the aperture width.
We want uniform lighting that produces as little shadow as possible, and allows for resolution of the small features on the buds, such as trichomes and hairs.
The general principles I'm working with are:
- As much light as possible
- Narrowest aperture possible, for greatest depth of field (But with the flash, this seems to be not actually true?)
- fastest shutter that produces acceptable exposure
- Low ISO
Am I on the right track here? I took a handheld shot with my iPhone 4S and it's sharper and more in focus than anything I've gotten with the DSLR yet... With the flash, the kit lens is actually looking the best so far, which doesn't seem right.
I've uploaded an album showing the camera enclosure and some test shots:
- Camera Enclosure
- Nikkor Micro 40mm, ISO 200, 1/200th, f/5.6
- Nikkor Micro 40mm, ISO 200, 1/200th, f/25
- Nikkor Micro 40mm, Flash, ISO 100, 1/200th (fastest flash sync), f/18 (Not sure why it's so unsharp! I can't really seem to get any good flash shots out of the 40mm Micro)
- Nikkor Kit lens @ 45mm zoom, Flash, ISO 400, 1/200th, f/20
- Handheld iPhone 4S
Thanks for your help!