Focus stack techniques
Adam Waring creates a focus-stacked food photo to show tasty treats in all their mouth-watering glory
Focus stack a fabulous food photo
The closer you are to your subject the less depth of field you have at your disposal, and this is a real problem with macro photography; to show the dazzling detail that only extreme close-ups can offer means that only a thin sliver of your subject will be pin-sharp in your photo, with the rest dropping progressively out of focus.
In food photography, the aim is often to show the product in larger-than-life detail with front-to-back sharpness to really tantalize the taste-buds, but even using a narrow aperture to increase depth of field, this will only extend to a centimetre or two at best when shooting up close and personal.
The solution is focus stacking. Focus on the front of the subject and take a shot, then focus a little further in and take another shot. Continue this process until you have a selection of images with different portions in focus, then stack them together in software such as Photoshop or Affinity Photo. This is an automated process that yields fantastic results. The only really tricky bit is ensuring that you have sharpness through enough of each image segment to create the pin-sharp composite, but this is made a doddle with some higher-end cameras that have Nikon’s Focus Shift feature.
Introduced in the D850, and found on mirrorless cameras from the Z 5 up, it refocuses through the entire stack for you, making the process simpler.
And the best thing of all about this project is that once you’ve shot it, you can eat it. Yum!
Set the scene
Set your subject against a window with indirect light. Put the camera on a tripod and compose to show the front, top and one side in frame, and focus on the front of your subject. With the subject lit from behind, the front is in shadow. Use a reflector to shine light onto your subject.
Dress the set
We placed our raspberry pavlova roll on a rustic wooden board, and gave it a sprinkling of icing sugar. We mixed up a little glycerine with water and brushed this onto a few berries to give them a sheen, which we scattered around the subject, and placed a few on top.
Shoot the sequence
We set a midrange f/8 aperture for optimum image quality with our macro lens. Focus on the front of the subject and take a shot, note where the image begins to drop out of focus and twist the focus ring until that bit’s sharp, and repeat the process along the entire length of the subject.
Automate it
If your Nikon has Focus Shift shooting, go to Photo Shooting Menu>focus Shift Shooting. Focus Step Width sets by how much the camera refocuses each step – 5 gave us good results. Set Number of Shots at 100, as the camera stops shooting once it reaches infinity focus anyway. Then hit Start.
Open the images
In Photoshop, go to File>scripts>load Files into Stack and select your shots. Ensure Attempt to Automatically Align Source Images is checked; we used a tripod, but the subject still changes size between frames due to focus breathing. Hit OK and your shots are loaded into a document as layers.
Stack it!
Click on the top layer in the Layers panel, hold Shift and click the bottom layer to select them all, then go to Edit>auto-blend Layers. Select the Stack Images option and ensure that Seamless Tones and Colors is ticked. Click OK and Photoshop will create layer masks to reveal only the sharpest bits of each image, for a pin-sharp composite that looks good enough to eat!