Heather Angel discusses how focus stacking can produce beautiful 3D images of plants

Photo Insight with Heather Angel

 

An internationally renowned photographer of the natural world and author of more than 50 books, Heather brings her expertise to AP

The plant you see here is called Nigella damascena, otherwise know as love-in-a-mist. It belongs to the buttercup family and one that has been grown in cottage gardens since Elizabethan times. When I first looked at this plant it was the arrangement of the flower and the leaves that really got me interested in taking a photograph. It’s a very three-dimensional specimen, which gave me food for thought when looking at it from a macro perspective.

When you’re shooting macro photography and want a little more depth and coverage of the subject, you stop down your aperture to give yourself a greater depth of field. However, this plant was a problem as there were so many components that were sticking out into the foreground and receding into the background. It’s a very complex structure, and one that is difficult to photograph in macro due to the fact that taking the aperture down to the maximum f-stop would result in a loss of image quality.

 Heather’s focus-stacked photograph of love-in-the-mist, comprising 41 images

As it’s quite a complicated plant, I wanted the background to be as simple as possible. That was important as I had all those fine bracts (leaves) all over the place. The background is a white board, which may not be the most exciting thing in the world, but when you’re working with such a fascinating plant you want all the attention focused on the subject. I shot the image using a Nikon D3 camera with a Micro-Nikkor AF-S 105mm f/2.8 lens, and lit the plant using a Nikon SB-900 Speedlight with a Honl sotftbox, which gave the image a lovely soft light. When you’re working with a white background you have to be careful not to cast a shadow on it. You must put the subject in front of the background and then light it from such an angle that the shadow falls outside of the field of view.

I soon realised that this plant would be an ideal candidate for a technique called focus stacking. Stacking is one of many techniques in digital imagery that help us when we want to produce an image where all plains of focus are pin-sharp. You could potentially apply the same kind of technique when working with film, but that would involve a lengthy process of scanning every frame and then combining them in post-production.

It is possible to take a focus-stacked image and focus on each plane manually, but there’s a great risk of inaccuracy. My method is to mount the camera on a focusing rail (sometimes called a focusing slide). The one I use is an American model called a B150-B macro-focusing rail (see right), which I bought from the US-based Really Right Stuff (reallyrightstuff.com), although there are plenty of other macro stages available in the UK.

The first thing to note is that there must be no wind, because if there’s even the slightest shift in the position of your subject it will throw your photograph completely out of balance and the individual frames won’t match up. You must also have constant light. As I’ve said, I used flash for this, but it was incredibly important that I mounted it on a lighting stand so the light fell in exactly the same place every time. Had it been handheld this wouldn’t have been possible.

When I had my camera mounted on the rail and the rail mounted on the tripod, I focused on the area closest to the camera. That’s the logical starting point. From there it’s a bit of trial and error because you need to work out how much to shift the focus each time. You change the focus by rotating the knob at the back of the rail, which then moves the camera closer and closer to the subject. As the camera moves forward, the focus moves further into the subject, so each frame has a different portion of the subject in focus. It’s worth experimenting because you may find that going by the measurement guide on the rail isn’t quite right for your subject. You may want to go in more or less than what it tells you. When you’ve taken your final frame, make sure that you’re focused on the furthest point.

If you end up with a huge number of images, you can always select every other frame rather than using every single shot – there are actually 41 frames in this image.

I used Helicon Focus (www.heliconsoft.com) to combine all my shots. Once you have your images loaded into the software, they come up as a series of thumbnails and you select which ones you want to use in your final image. It could be every single shot or every other one. The software will then match up every frame and produce your final image. It doesn’t take long and the results can be absolutely stunning.

A lot of people know about focus stacking, but few put it into practice. It’s now possible to produce images of flowers that are three-dimensional and actually quite close to how a painting would look, as each part of the image is in focus. It’s a beautiful effect and I wholly recommend giving it a go.

Heather Angel was talking to Oliver Atwell

To see more images by Heather visit www.heatherangel.co.uk or www.naturalvisions.co.uk. Heather regularly runs workshops at the British Wildlife Centre. For information on courses run by Heather and her son Giles, visit www.photographyandphotoshopcourses.co.uk