Depth of Field in Macro Photography
2 Depth of Field in Macro Photography
Adjusting composition for greater depth-of-field
Take a look at the image below. In comparison to the robber fly image we discussed on the previous page, this fly was shot using both a wider aperture and at a higher magnification ratio. This means beyond doubt that DOF is smaller. Yet, the image doesn’t lack for greater DOF. Almost the entire fly is in focus.
The difference here is that the subject was shot from a direction which enabled me to fit most of its interesting parts along a single plane of focus. Remember that DOF controls how far in front of and behind the point of focus can be rendered in sharp focus. Yet all points in the scene that exist at the same distance from the lens can be in focus simultaneously, no matter the amount of DOF available. What I've done here is to carefully position the camera so that all of the parts I want to be in focus fall along a plane that is parallel to and therefore equidistant from the lens. The fly’s side is relatively flat, so by adjusting the camera lens to be parallel with the fly's body, I managed to get sharp focus on all of the body parts which stand out the most.
|A fly shot from the side. All important parts are in focus, even though DOF is extremely shallow.|
It’s very important to understand that we have not extended DOF. It is still extremely shallow. Look at the fly’s front right leg. It’s only a millimeter behind its front left leg, but still out of focus. Shallow DOF is also visible in the wings. The section closest to the viewer is focused, the part farther away is out of focus. The point is that although DOF is shallow, if the subject is flat enough we can shooting at an angle parallel to the subject and produce an image with satisfying focus.
While this method might seem very basic, it’s by far the easiest and most common method of dealing with the DOF problem in macro, and is definitely the first method I teach all students. It’s easy to use – just remember to be parallel to the subject’s body. Since arthropods usually have at least one flat side, this method is very effective with a wide range of subjects.
Let's examine another image. The Levantine leopard (Apharitis acamas) shown below was shot using an aperture of f/8 - which is relatively wide for macro work - but still I managed to get focus from head to abdomen, including the wings. When shooting butterflies it’s important to remember that one needs to be parallel not along the right-left axis (with both head and abdomen existing at the same distance from the sensor), but also along the up-down axis (with both body and wings at the same distance from the sensor).
|Butterflies have very flat bodies. This makes shooting them from a parallel angle very effective for maintaining focus over the entire body.|
Faking depth-of-field: Focus Stacking
So problem solved, right? Well, not quite. What happens if we don’t want to shoot parallel to the subject? It’s extremely limiting to constrain our shooting angle this way every single time we photograph. Sometimes we want to view the subject at a frontal angle or even a diagonal. And of course some subjects have such irregular shapes that they have no flat side! Think of protruding body parts such as antennae, a proboscis and wings.
|This robber fly has no flat side,
and so shooting it from a parallel
angle is not a viable option. Here
the eye is in focus, but little else.
|Another shot, this time with focus
on the mustache and proboscis,
but now the eye is out of focus.
Luckily, the digital revolution has brought a very efficient method of actually increasing DOF. It is called 'focus stacking' and I’ll be covering it in detail in an upcoming article. Simply put, focus stacking is a process that involves two stages. First, in the field, you shoot a series of images with identical composition, each focused on a plane of different depth on the subject’s body. For example, one shot can be focused on the eye, the other on the proboscis, and so forth. You shoot as many images as you need. The main rule is that every part of the subject you want to appear sharp in the final image must exist in sharp focus in at least one image of the series.
|By combining the images above via focus stacking, we achieve a result
that has both detail and sufficient DOF.
Next, in the comfort of your home, you can use any number of software programs which automatically select the focused parts of each image and stack them together - hence then term 'focus stacking' - into a composite image that exhibits a wider DOF than you could ever hope to capture in a single exposure.
Focus stacking is a fantastic innovation for the macro photographer. And while it does take more time and careful preparation in the field, there just isn’t a better way of obtaining both detail and increased DOF in extreme magnifications.
|A praying mantis portrait, created by stacking two images. Without focus stacking, either the mouth parts or the eyes would have been out of focus.|
With these new tools in hand I don't want to leave you with the impression that shallow DOF is inherently bad. On the contrary, it is one of the most effective compositional tools at our disposal. By purposefully using shallow DOF you can create a dramatic appearance and lead the viewer’s attention to specific elements in the scene, control that is critical to success in every style of photography.
For further reading on macro photography take a look at Erez's previous articles in this series:
The what and why of wildlife macro photography
What we want in a macro shot - Detail
What we want in a macro shot - Background
What we want in a macro shot - POV and special scenes
Macro photography: Understanding magnification
Erez Marom is a professional nature photographer and photography instructor based in Israel.
Erez will lead a macro and nature photography workshop in Costa Rica in July 2012, where he will explain his photography techniques and methods with which he achieves his unique results. Registration is open for this unique opportunity to learn first hand from one of the world's leading macro artists.
You can see more of his work at www.erezmarom.com and follow him on his Facebook page and
|Umbrellas by pleytime|
from An A to Z of Subjects- Week 21, U
|Glass ball on a perforated metal plate _2 by harubux|