Flower Photography of Anita van Rooy

Dark Red Peony
1. Extending Depth of Field

Flowers have always been one of my favorite subjects to photograph. But I have often been frustrated with the difficulty of getting them tack sharp from front to back. You can increase the depth of field by stopping down to smaller apertures. But that also brings the background more into focus, adding a distracting element that doesnít compliment the flower. And those tiny apertures reduce image quality because of diffraction.

Delicate Pink

Burgundy and White Iris
Now, thanks to Photoshop (I am using CS2), I have resolved the difficulty by using the techniques I describe in this article. First, I extend depth of field by combining several photographs taken at different focal planes throughout the flower. This yields a composite image with the flower in focus. The method is similar to tomography in radiology. Second, I occasionally create a new background for the composite image.

Setting Up

A sturdy tripod is required, of course, and I recommend using a high-quality focusing rail. You can use the popular macro lenses, but I prefer a zoom lens with an added Nikon "close-up" diopter lens. This configuration allows me to move in close, but also makes it easy to adjust the focus plane without moving the entire camera rig. Easy and precise adjustment of focus is critical to this technique.


Inside Magnolia
I typically start by examining the flower from a side view. It is very important to study the flower and recognize which parts are closest to the camera, which are furthest away, and where the in-between parts are placed. If necessary, sketch a rough diagram to keep at your side while making the photograph. Get comfortable, because youíll be studying the viewfinder with much more care than the usual photograph.

Making the Exposures

I begin by focusing on the very closest part of the flower, and make an exposure. Then I advance the focus gradually deeper into the flower while making additional exposures. All the while be very careful not to bump the camera or let a breath of air move the flower.

Yellow Water Lily

Pink Columbine
The number of photographs required depends on the depth of field (which you can vary with aperture) and the topography or depth of the flower. With a little experience youíll know how much to advance the focus between shots: too much and you may find youíve skipped an important layer, leaving part of the flower out of focus.

Hint: after completing the series of photographs, photograph something different (maybe your hand or the grass) as an end marker.

I recommend shooting these photographs with your digital camera in RAW mode. Not only does this allow maximum quality, but you can ensure that all the photographs in your series are processed identically (in particular with the same color temperature). Only the plane of focus should be different between images.

Purple Columbine

Stacking the Layers

When all the images are converted and opened in Photoshop the fun begins. Start with image 1 (the closest one) and enlarge it "fit to screen." Then, while holding the Shift key, drag image 2 right on top of it. Holding the Shift key ensures that image 2 is placed exactly in the middle of image 1.

Pink Orchid
Now, with these two images stacked in layers, change the blending mode of the top image to Difference. Where the images are perfectly aligned the appearance will be black on screen (temporarily) Ė this is what you want to achieve. Where the two images are misaligned and some adjustment is needed, the differences become visible. Use the arrow keys to nudge the top image into place so the difference shows all black. You may also need to use Free Transform to scale the image to match the other image. That is because adjusting focus (or moving in with a focus rail) may change the apparent size of the subject slightly.

Open Orange Tulips
Once you have the two layers aligned as best you can, change the blending mode of the top layer back to Normal.

Masking Sharp Areas

The next step is to create a Layer Mask on the upper layer. Then use a brush to paint on the layer mask, exposing the sharp (in focus) parts of the layer and hiding the rest (they will be masked). Now you begin to see an increased depth of field bringing more of the flower into focus. Pay particular attention to edges that border against the background, as they are most significant to the eye and should be in sharp focus.

White Iris

White Wild Hibiscus
Repeat these steps for all the images in your series, starting by dragging image 3 onto the layer stack and aligning it using Difference mode. When all of the images are processed this way you should find that the whole flower is very sharp from front to back.

[Editorís Note: several software programs are available to automate both the layer alignment and masking of focus regions. Even Photoshop now comes standard with alignment and blending automation. Automated software may alleviate some of the meticulous Photoshop labor, but in some cases the results from manual work is superior.]

Updated 20-aug-11   Contents copyright © 2001 - 2011 PhotoCentric.Net, All Rights Reserved