Master Focus Merging
Get to grips with this powerful Affinity Photo tool and learn how to focus stack for richly detailed close-ups
Close-up photography lets you see the miniature world in incredible detail, but it can be a challenge for all sorts of reasons. First you need the right kit, such as a macro lens, a tripod and possibly a focus rack. Then there’s the challenge of composing and framing tiny subjects. On top of this, one of the biggest difficulties is the limited depth of field.
The closer we are to a subject, the less the depth of field – the plane of in-focus details – will be. Of course, with macro photography we usually need to get in very close to the subject, often with it right up to the front of the lens, so our depth of field will naturally be very shallow. Even when using narrow apertures like f/16 the sharp area may only stretch to a few millimetres.
As such, if we want a greater area of sharpness there’s only one option: we need to shoot for a focus stack. Essentially this involves using a tripod and shifting our focus point over several frames. Once done, we need a tool for combining all the sharp parts into one super-sharp image. And this is where Affinity Photo’s fantastic Focus Merge command comes in. Find out more at affinity.serif.com/photo
1 Prepare your images
If you’re merging a lot of photos (we had 50 frames here) then consider resizing them to speed things up, as it can take much longer to merge full-res raws than resized jpegs. You can use Affinity Photo’s Batch command to convert raws to resized jpegs. Go to File > New Batch Job, then choose your folder of images, check jpeg and choose a resolution.
2 Add your photos
To start focus stacking go to File > New Focus Merge. Click the Add button and navigate to your folder of focus stack images. Hit Cmd/ Ctrl+A to select them all (or Shift-click between the first and last to select files), click Open then OK to begin merging. It’s great to see the process unfold over a few seconds, as the sharp areas are detected and combined into a depth map, then finally merged into a single sharp image.
3 Watch the edges
As your focus point shifts the field of view will change slightly, as if zooming in or out. As such, the furthest focus point will reveal more detail around the edges of the frame, but these edges will be removed when the Focus Merge command aligns the sequence. Bear this in mind when composing, as you might find that important parts of the subject will be cropped. It’s best to compose your image while focused on the closest point.
4 The Source Panel
The Source panel houses a list of the images that make up your focus merge, which can show how good your merge has been. The top Source layer is your combined focus stack, but you can highlight any source layer, then click the eye icon at the bottom to toggle a view of the frames making up the stack. You can check to see if a sharper detail has been omitted.
5 Clone from Source layers
You can clone from any Source layer into your finished image. Some details may look blurry; this usually happens with fine highlight details or overlapping petals. Check the Source layers and if you find a sharper detail you’d like to include, highlight the chosen layer, grab the Clone tool and toggle the Source Preview icon to return to a view of the merged image, then paint to clone the sharper details.
6 Final Cloning
Some areas will be smudgy not because the focus merge tool has gone wrong, but because they have been obscured by blurry details. There will be no Source layer with sharper details to clone from, so we will need to copy sharper details from nearby. Go to the Layers panel, make a new layer and grab the Clone tool. Set it to ‘Current Layer and Below’. Alt-click to target a suitable area and clone to tidy up.