Macro Photography on Steroids
In the last issue of this journal (#103) we looked at ways of getting nearer to your subject, closer than the “minimum focusing distance” of your lenses would allow you to get. Most ordinary lenses give you a maximum of 0.25x magnification, which means that a 14.4 cm large object will fill the whole frame (assuming you use a full frame camera).
As we saw last time, there are a few tricks which allow you to get into macro photography without breaking the bank, like using close-up lenses and extension tubes. Of course, dedicated macro lenses are more convenient, and they can take you beyond 1:1 magnification, but they come at a price.
Another problem with closeup photography is the limited depth of field (DoF). You get a chilly 1.12mm at f/8 when you get down to life-size (1:1). The DoF increases when you stop down your lens, but it is usually not enough to get your entire flower or insect into focus. Secondly, diffraction will make sure that nothing gets tack sharp anymore. For that reason you shouldn’t go beyond f/16, even if your lens allows you to stop down to f/32.
In some cases, you don’t want everything to be in focus, even in macro photography. Have a look at the dandelion (Image 1) taken with a full frame camera at f/13. It would be distracting if all the white floaties in the fore- and background were in focus.
Image 1 – Dandelion focused on the centre at f/13
In most cases, however, we need more than one or two millimetres of DoF. And the digital age gives us a simple solution!
This is one of the great byproducts of digital photography. Simply put, focus stacking is a two-step process. In the field, you shoot a series of images of your subject, each focused on a different plane of focus from the camera. For example, let’s take a portrait of an insect. You start with a shot focused on the parts closest to the lens, usually the antennas, then comes the eyes, and you keep shooting until you have the last wingtip in focus. The main rule is that every part of the subject you want to have sharp in the final image must be in sharp focus in at least one image of the series.
The second step is to combine the whole stack of images on your computer in a way that only the sharp parts of each shot are combined into the final image.
There was much excitement when Adobe Photoshop CS4 came out, back in 2008, with a ‘Stack Images’ feature and an ‘Auto Blend Layers’ command. The program compares the layers and masks them in an attempt to keep the highest contrast areas of each layer. In-focus areas will normally show the highest contrast, whereas out-of-focus areas will have lower contrast. This is the theory; the results were disappointing.
However, we have come a long way since then. Today’s Photoshop editions will give you excellent results. Open your stack of images in Lightroom, then choose ‘Photo Edit in’ > ‘Open as Layers in Photoshop’. Once that’s done, select all the layers and run Edit > ‘Auto-Align’, followed by Edit > ‘Auto-Blend Layers’ choosing the stacking option. Grab a cup of coffee while the computer crunches through your stack of images. Hopefully, you have at least 16GB of RAM.
You can find programs on the market dedicated to focus stacking, and they give you more control over the process and noticably better results than Photoshop. They are certainly faster and put less strain on your hardware. One popular program is Zerene, but it doesn’t support RAW files. Helicon Focus from HeliconSoft is probably the bestknown stacking program and I want to give you my experiences with this program and show you some results.
This program costs between 48 and 104 NZ$ for a 1-year licence, depending on the features you need. There is also a lifetime licence available, and you can upgrade at any time. Helicon Focus offers a free 30-day evaluation time to allow you to test-drive the program and check out all its features.
HeliconSoft has been around since 2003, and the regular updates have made the program intuitive and straightforward to use. You’ll find plenty of resources on the internet, including YouTube videos to get you going.
The program will read JPEG, TIFF, BMP, PSD and – yes, even camera RAW files. You load all the files of your stack and tick those which you want to include in the calculation, then you press the ‘Run’ button and watch the image slowly coming into focus.
There are several parameters to fine-tune the process. You can select different algorithms, but the most important parameters are ‘Radius’ and ‘Smoothing’. Radius defines the size of area around each point which determines if that particular point is treated as focused or not. Smoothing characterises how the focused parts are combined. This is important for ironing out the transitions, without creating artefacts.
If an image has fine details, then a smaller Radius setting will give you better results. Lower Smoothing values will produce a sharper image, but the transition areas may show some artefacts. It pays to vary the Radius and Smoothing settings and press the Run button again. The results are going to be listed in the Output section and you simply pick the best-looking image.
Other variables are the auto adjustments for vertical/horizontal shifts, rotation between individual frames as well as changes in magnification and brightness. This is critical because subject movement between the frames is unavoidable. Stereomicroscopes, for example, will only use one ocular for the camera and will shift the subject sideways when changing the focussing distance.
Very important is the ‘Retouch’ feature. Sometimes the program creates artefacts on the final image. Often it is a halo around bright edges on a smooth background. Or an object in the foreground masks some detail behind it. In that case the program allows you to clone detail from one of the individual shots into the final image.
Some Photographic Tips
The size of the object should not change from frame to frame. When using a macro lens, it is best to vary the distance between camera and subject, rather than refocusing the lens. A macro focusing rail (Image 2) mounted on a sturdy tripod is highly recommended. Cable release and mirror lockup will reward you with tack sharp images.
Image 2 – Macro Focusing Rail
Needless to say, your subject must not move, crawl or fly away while you slice it with your camera. The slightest breeze will throw a spanner in the works even for static objects, like flowers. It pays to bring your macro subjects indoors. Image 3 shows you a 2-day old tomato plant. It is a composite of 30 layers taken with a ring flash at f/5.6. All macro shots shown here were taken with a Canon MP-E 65mm f/2.8 1-5x lens.
Image 3 – Two-day old Tomato Plant
Live insects tend to get nervous with the proximity of so much hardware and they are very challenging subjects! Spiders, on the other hand, are more relaxed and if you find one within reach of your tripod it will allow you to set up your gear and won’t even blink when confronted with a flash. Image 4 shows you a live spider at 5x magnification, made up of 44 individual shots using a ring flash and f/5.6. The program handled the eight legs remarkably well.
Image 4 – Live Spider
Chinese wax scale insects are not the prettiest of animals, but they give you plenty of time to set up your gear – and they are tiny. They love feijoa leaves, and that’s where you can find them (Image 5). The little devil in the picture is a full 2mm across. It can easily be blown up to A3-size – a magnification of 150x! This shot was taken at 5x, f/5.0 using a ring flash. Twenty-five shots were combined to cover the depth of field of about 1.5mm.
Image 5 – Chinese Wax Scale Insect on a Feijoa Leaf
Focus stacking also lends itself to landscape photography, if you want a nearby object as well as the background in sharp focus. In that case you simply change the focus, and you might even get away with a hand-held camera.
Focus stacking is a fantastic tool for the macro photographer. Having said that, I don’t want to give you the impression that a shallow DoF is inherently bad. On the contrary, it is one of the most effective compositional devices in the photographer’s toolbox – remember the dandelion in Image 1!