Monday, January 7, 2008
Unlimited Sharpness With Helicon Focus
Helicon Focus gives you the ability to cheat depth-of-field limitations
The basic concept underlying Helicon Focus is deceptively simple. The photographer takes a series of matched images, overlapping the focus of each shot with the next until the entire field is covered. Helicon Focus automatically adjusts and resizes the images, which is important for macro photography, and it equalizes the brightness of adjacent images. It then merges the frames, retaining only the in-focus portions of each image. The result is a sharp composite. With advanced planning while capturing shots, the photographer can control the areas of focus as desired.
Despite the realignment capabilities of the program, it's necessary to work as precisely as possible, using a tripod and, for macro photography, a focusing rail to assure that each shot matches the adjacent frames. Use a remote release and lock up the mirror if needed to minimize camera movement. Then, follow these steps.
• Determine the area that needs to be rendered in focus—it need not be the entire field of view. That is, the bug could be in focus while the leaves behind it are blurred.
• Set the camera to manual focus, and turn off image stabilization.
• Use manual exposure, keeping the shutter speed the same throughout the series.
• Choose an ƒ-stop that offers optimal sharpness (generally, ƒ/11 or ƒ/16) and enough depth of field so that the focused area in each shot can be overlapped with that of the preceding image.
• If you want to maintain an out-of-focus background, choose a large ƒ-stop (ƒ/5.6 or ƒ/8). It will take more images to capture the sharp area, but you can retain the soft background effect.
• Move the focus through the field of view by turning the focusing ring to capture a series of shots that achieve the desired overlapping increments. In macro, it may be necessary to adjust the camera/lens combination along a focusing rail, moving the working distance to change the area of focus.
Be on the lookout for the following potential problems:
• The subject can't move during the series of exposures. If the subject is influenced by wind, you may need to photograph in early morning or late afternoon or find a way to stabilize it. It's possible to use Helicon Focus on live subjects, but you need to work quickly.
• Large foreground features can be problematic. As the focus shifts past them, they tend to “bloom” out of focus and obscure the areas behind. Choose an angle of approach that minimizes the foreground's impact on the total field of view. Experiment with different perspectives.
• If your composite image shows bands of softness interspersed with sharp areas, you haven't sufficiently overlapped one or more images in the series.