Keeping it all in Focus

If you have read some of my past blog's you may recollect I have mentioned the term 'depth-of field' on a number of occasions. Depth-of-field is important as it determines how much of your image is in focus from near-field to far field.

Depth-of-field becomes particularly important when:

- you open up the aperture of your lens to let more light in (this reduces the depth-of-field)

- the closer you are to your subject, the narrower the depth-of-field. This is particularly obvious when doing close-up Macros photography where the depth-of-field can be frustratingly narrow ( measured in mm).

The good news is there is a solution to help overcome the problems and this is termed focus stacking. Focus stacking is a technique used to increase depth of field in a shot with post production. So exactly how does focus stacking work you may ask?

Well, focus stacking simply means taking multiple photos of the same subject, each with a different focused spot. This is followed by the use post-processing software like Adobe Photoshop CC to align the focused portion of each image into one final-and-focused image. It is a really simple technique that everyone can use on their photos.

Example of Before and After Focus Stacking

Taking a photograph looking down the bridge of an acoustic guitar:

Guitar Before Focus Stacking

Guitar after Focus Stacking

What equipment do you Need?

You will need a tripod and a remote trigger to maintain the camera in the same position for each of the photos in the focus stack.

You will also need Photoshop CC or Photoshop Elements as previously mentioned to post-process the photographs into a the final image. Also Affinity Photo will do Focus Stacking and is a cheaper option but your choice may well be influenced by other features and considerations.

How to shoot the photographs in the focus stack

Typically you will need to take 3 photographs. The first at the nearest focal point to the lens, the second about a third of the way into your scene and the final shot at infinity. If you are doing close-up macro photography you may need to take several more shots depending on the nature of your scene.

Set your camera to focus on a single-point or AF-S. (Cameras can be set to a number of options including single point or multiple point). You can move the single focal point around in the frame to centre on a particular object in the scene on the majority of DSLR Cameras. Set to the correct exposure for your shot and then take your first shot.

Set your camera to manual mode and adjust the focal point to an object around a third distance into the scene and take the second shot.

Lastly adjust the focus point out to infinity and take the last shot.

Post-Processing in Photoshop CC

Open the photographic images as layers in Photoshop by choosing File > Scripts > Load Files into Stack - select 'Attempt to Automatically Align Source Images'.

Opening Images in Photoshop

Once the images are in a stack in a single Photoshop file, select the layers in the Layers panel and choose Edit > Auto-Blend Layers. In the dialog that appears, select Stack Images and (optionally) turn off Content Aware Fill Transparent Areas. Click OK.

Photoshop then creates a layer mask for each layer that allows the sharpest areas to remain visible. You can see the layer masks applied in the following figure in the Layers panel in Photoshop.

Blending the Images into a 'Photo-Stack'

Now that you have a focus-stacked image, you can apply tone, colour, and other adjustments as desired to produce the final image.

I hope you found this blog useful. Constructive comments always welcome. Please note the photographic images that appear on this blog are not full/high resolution. High resolution images (plus many others) can be purchased as professional quality prints or mounted on various media through my on-line shop.