How to take pictures of ice crystals using Macro lens?

Question

I am using AF Micro-Nikkor 60mm f/2.8D lens (mounted on Nikon D3400) to get some pictures of ice generated on a flat surface with controlled LED lighting . I am trying to take very close up shots of an ice surface (ice crystals in fine details) and need a deeper depth of field. How can I find the sweet spot for the best focusing? Also, in specification, the minimum focus distance is 0.72 ft. Does that mean how close the camera can be from the object? I am taking pictures in still condition. Does that mean that I can use a very slow shutter speed (such as 1/30)?

This is a lab experiment and I am not using natural light which does not allow me to use higher f/stop and low ISO at the same time.

I am using controlled LED light (not too close to ice surface).The camera is mounted right over the surface and movement is controlled by a stepper motor.The camera does not take picture when it moves rather it stops and takes pictures and again moves,then stops and takes pictures of another spots.Since the camera isn't moving when taking pictures I assume shutter speed 1/30 would work and f/stop 22 would give me a deeper depth of field. However, the images aren't sharp enough to understand the crystal clearly.

Answer 1

The minimum focus distance is indeed the minimum distance you'll need to take (from sensor to subject) to be able to focus. The lens can't focus closer than that. A way to get around this is with an extension tube which lets you move the lens closer to the subject and increases magnification at the cost of some light.

If the ice is stable and you have the camera firmly mounted you can go with slow shutter speeds, possibly slower than 1/30. If that helps to use a narrower aperture (higher f-stop) then you could increase the depth of field that way. You can also try to reduce vibrations by using a remote shutter button and the mirror lockup function if the camera has it.

Even with all that, macro shots can have very, very thin depths of field. A flat-looking ice crystal might still have too much relief to get everything as sharp as you want. At that point it's interesting to look into the technique of focus stacking. This means taking multiple pictures at different focus distances (although still very tiny differences in absolute terms) and then having parts of those pictures combined to get one image with substantially more in focus. Your subject has the advantage of not suddenly flying away or moving around like with plants or animals, which can make the technique easier to apply.

Answer 2

Since the camera isn't moving when taking pictures I assume shutter speed 1/30 would work and f/stop 22 would give me a deeper depth of field. However, the images aren't sharp enough to understand the crystal clearly.

At f/22 you're getting general softness due to diffraction. The D3400 has a DLA of around f/6.

Open up the aperture of your lens to around f/5.6-f/8 and use magnified Live View to focus manually.