Little things that count
Focus stacking is a viable way to ensure total picture clarity.
THE other day the conversation turned to the subject of macro photography and the art of taking pictures of very small objects.
The problem, as we are being reminded constantly, is that it is almost impossible to get the front, back and everything in-between of a small object in focus at the same time.
Devotees of the great David Attenborough will know his camera wizards have invented a new type of lens just for the purpose of taking video of an ant in focus in the foreground with a presenter, also in focus, behind.
Compact cameras, with their inherently greater depth of field because of their small sensor area, cope well with close-ups. As the sensor gets larger, right up to full frame, focus becomes more of a problem. Using a dedicated macro lens on a DSLR, stopped down to just before the f-stop where diffraction becomes a problem, is a starting point.
With critical focus, low ISO, small aperture and a slow shutter speed, a tripod and remote release (or at least using shutter timer delay) are essential, but even then front-to-back focus can be difficult.
The solution may be focus stacking.
Suppose the subject is a dandelion with a leaf sticking out of the stem. If you want everything, from the far edge of the seed globe to the tiny seed wings on the front, to be sharp, give focus stacking a try.
Set the camera to manual focus and exposure and take a series of shots, focusing sequentially from the back edge to the front of the subject.
DSLRs don't have the best-focusing screens for this job and it is a counsel of perfection to replace the default screen with a plain matte glass type, something that is easy on some cameras and nearly impossible on others.
Anyway, it is only the sort of thing you would do if you intend to take thousands of photos of insects, jewellery, coins, toys or small flowers.
Four to five exposures is usually enough to cover every plane in the subject area. For processing, you need software that will align and blend the images into a single, sharp photograph. Photoshop CS5/6 will do it, as will PhotoAcute ($149, photoacute.com). Picolay is free (picolay.de) and does a reasonable job but is slow aligning images. Zerene ($89 from zerenesystems.com) is also very slow but has good output if you use Stack/Align and ''stack all (both)'' for best results. There is a 30-day trial version.
In Photoshop the process is: open Bridge and locate image set. Select images. Go Tools/Photoshop/Load files into Photoshop layers. Photoshop opens with layers stacked. Select all layers. Hit Edit/Auto-align layers/Projection Auto. When that's done, hit Edit/Auto-blend layers/Stack images. When the process is complete, flatten layers. The result is miraculous.
Photoshop CS5/6 and PhotoAcute do the best job and Zerene is the cheaper alternative. Be prepared to experiment with the arcane settings.