Depth of Field for Close-Up Photos
For non-macro photography, your subject won’t be especially close to your camera – maybe 5 or 6 meters, or even as far away as the horizon. At these distances, a normal aperture of f/8 or f/11 typically will render a sharp scene from front to back (aside from extreme telephoto shots, since telephotos have less depth of field).
Macro photography is different. When you take close-up photos, you naturally end up with very little depth of field, even at small aperture values. At 1:1 magnification, your depth of field may be so thin that you can’t get a fly’s head and feet both to appear sharp at the same time, even though they are just millimeters apart!
The thin depth of field is related to another challenge of macro photography: You don’t have much light. Why not? There are four main reasons why you’ll have to work with very little light in macro photography:
- Your camera itself usually blocks some natural light.
- Your flash might not point at the right angle to illuminate your subject.
- Apertures like f/11, f/16, or smaller are necessary in order to get enough depth of field, but they reduce light.
- You’ll need to be at very fast shutter speeds in order to reduce blur from camera motion (which is magnified for close-up photography), also darkening the image.
With all these issues together, your close-up photos can look like you’ve left on your lens cap in the middle of the day. So, how do you balance depth of field with capturing enough light? There are a few ways, each with their own compromises.
Method 1: Open Up Your Aperture
You may choose to live with a thin depth of field for your macro photography – to the point where you won’t be able to get an entire ant head to appear sharp at the same time. If that seems fine to you, just open your lens’s aperture as wide as possible (or only slightly stopped down – something from f/2.8 to f/5.6), and you’re set to take macro photos.
The benefit of this approach is that you don’t have to worry about complex lighting setups or software fixes to make your macro photos look good, since you’ll generally capture enough light to make things work. The downside is that it becomes nearly impossible to focus your lens handheld at the closest magnifications, since there is essentially no depth of field.
For that reason, this method works best if you are trying to take photos of subjects that are a bit larger, in the range of 1:4 to 1:10 magnification. However, I do not recommend it if you want to take life-size photos at 1:1 magnification.
Method 2: Stop Down and Use a Flash
The next method (and the one I use the most) is to stop down the aperture to a small value. By small, I mean f/16 or f/22. The upside to using such a small aperture is that it is easier to get your subject to appear in focus – though still tough – and your depth of field becomes manageable.
However, a flash is essentially mandatory with this method, since you are losing a huge amount of light. On top of that, diffraction starts to have a noticeable impact on the sharpness of your photos. Still, it is important to keep in mind that an f/22 image with diffraction looks far sharper than an f/4 picture without any depth of field.
Method 3: Stack a Set of Macro Photos
Another method is focus stacking. It involves taking your photos at more “moderate” apertures, with lower diffraction but a shallow depth of field (usually f/8 or f/11).
To counteract this tiny depth of field, you take several photos at different focus distances and combine the best parts of each in post-processing. For example, you may take one photo where a bug’s head is in focus, one where the wings are in focus, and a third where the back legs are in focus. Then, you can merge them into a sharp bug photo from front to back. We have a separate tutorial on focus stacking at Photography Life as well.
There are two upsides to this method: First, image quality is extremely high, since diffraction is a non-issue. Second, you have the ability to extend your depth of field artificially so that any subject can be completely sharp from front to back, even at especially high magnifications.
The downsides are numerous, however. Focus stacking is typically confined to studio and tripod work because precision focus is required. Another downside is the time involved. For maximum quality, you may need to combine dozens of photos into a single picture, which can take hours of photography and post-processing. You also need specific software to combine focus-stacked images (such as Photoshop or Helicon Focus), with better and more specialized options generally costing more.
The biggest issue, though, is that your subjects need to be completely still. It is possible to find bugs that aren’t moving, but it isn’t always easy. This method works best for plants, or bugs that are drowsy and waiting for the sun to come out (try the early morning).
This is also a fairly costly option, because you will need a decent amount of dedicated equipment. A solid tripod, a tripod head, a macro focusing rail, and special software are all requirements for the most dedicated focus stackers.
Method 4: Tilt Your Plane of Focus
The final way to increase depth of field is to buy a special type of macro photography lens: a tilt-shift. These lenses let you tilt the depth of field along your subject. For example, you may be able to focus simultaneously on a bug’s head and wings, even though both are different distances from the lens. Potentially, you can get an entire bug to be sharp in a single photo at much more reasonable apertures than normal.
There are many downsides here, though. First, tilt-shift macro lenses (like the Nikon PC-E 85mm f/2.8D) cost at least $1000 used and up to $1800 new. They generally don’t focus to 1:1 macro (about 1:2 instead), they only focus manually, and they are difficult to use without a tripod. Lenses like this mainly shine for studio work of non-moving subjects, in which case focus stacking may be the preferable option. That is not to say this method is always a bad one, but that it is very specialized, and most photographers will not find tilt-shift lenses to be the best option overall.
Which Method Is Best to Capture Enough Depth of Field?
Most macro photographers use a combination of the above methods depending upon the situation. Personally, I tend prefer to use a flash and a small aperture for high magnification macro photography. If I am taking pictures of larger subjects like dragonflies and lizards, I will use a wider aperture and shoot in natural light. With practice, though, the key is to realize for yourself which scenarios demand each of these methods, making it easier to set your camera appropriately.
The next step in taking good macro photos is to focus properly. I will cover that process on the following page of this tutorial, including some details that may be different from what you would expect.