Using in-camera focus bracketing to extend your depth-of-field

Focus Bracketing in the Lumix G9

All current Lumix G models offer an in-camera focus stacking mode that is easy to use and which avoids the need for post-capture software when we want to extend or control our depth-of-field. This feature is accessed via the Post Focus mode, and comes in 4K and/or 6K varieties according to the camera you are using. It is a useful feature, and with the JPEG colour and contrast controls Lumix cameras offer, it is highly flexible if you take the time to make the most of your settings so that post-capture manipulation can be minimised – or avoided.

The downside for some of the in-camera mode is that it produces only a JPEG that has limited manipulation possibilities after the event, and that the system finds it hard to cope with extreme situations.

An alternative to using the in-camera stacking mode is to shoot a series of images with different focus positions which are then loaded into focus stacking software. Computers tend to have greater processing power than cameras, and so can deal with much more complex and intensive tasks so we can choose to shoot in Raw or JPEG formats as we prefer. Fortunately Panasonic has a function in its newer models that is a great help in creating the images needed to feed into focus stacking software – it’s focus bracketing.

How it works

Focus Bracketing with Lumix cameras

The focus bracketing mode automatically shoots a series of images at a range of different focus positions so that we don’t have to shift the focus ourselves and risk moving the camera between frames. Users can decide how many pictures are taken, how far apart the focus positions are and the order in which the focus positions are covered. These controls combine with our choice of aperture settings to allow us full control of the situation. The controls offered are:

Focus Bracketing with Lumix cameras

    • Step – This governs the distance the focus point shifts between pictures. We can choice options between 1 and 10, with 1 representing the finest movements and 10 the greatest.

Focus Bracketing with Lumix cameras

    • Image Count – This covers how many images will be taken in the sequence. We have a choice of between 0 (which obviously wouldn’t be much use) to 999 for extreme situations. It is cool to be able to shoot a massive pile of pictures to get extreme depth of field, but remember you need a computer that is capable of stacking them so don’t overdo it. Focus stacking can be pretty intensive for any computer.

Focus Bracketing with Lumix cameras

  • Sequence – By default the sequence is set to 0/-/+, but we can chose 0/+ if we prefer. When we select the first option the camera’s first picture will be at the focus point we selected, and then it will pull the focus closer for the next shot and then push it further away for the third. A fourth picture will be focused even closer than the second shot, and a fifth further away than the third shot – and so on. This mode brackets around the selected/main focus area, allowing us to collect images that can be used to extend the depth of field forward and behind this point.If you use the 0/+ option you should focus on the closest part of the subject that you want sharp, as the system will shoot focus points gradually further away from the camera. This mode sends all the extended depth of field behind the initial focus point.
  • Aperture – When shooting for focus stacking it makes sense to use the best apertures your lens has to offer rather than going for those that deliver the most extensive depth of field but which also reduce image sharpness. You’ll find these apertures in the middle of the range, and they will be f/5.6 and f/8. When you close an aperture much smaller than this sharpness drops off a little due to diffraction. As we can replace the effect of the depth of field we’d get from a smaller aperture with more frames from a wider and sharper one, we should do that.

Once the parameters are set a press of the shutter button triggers the sequence. The camera fire-off all the required shots in one go, shifting the focus distance between frames. We can choose to use electronic shutter to avoid any shake caused by the shutter between frames. The slightest movement could reduce detail and make aligning the images more difficult. Obviously you’ll need a tripod for this to ensure the camera doesn’t move between frames, and using the Panasonic Image App to trigger the camera wireless is a good idea.

Combining the elements

Focus Bracketing with Lumix cameras

This sequence of nine pictures was shot at f/5.6 and with a Step setting of 4. The aperture provides a moderate depth of field so I needed finer movements (Steps) to ensure the areas covered by the depth of field would be able to join up when the images were stacked.

The number of pictures we need and the distance we need the focus to shift depends partly on the depth-of-field our chosen aperture will give us and the amount of the scene we need in focus. A wide aperture, such as f/2.8, will deliver a tiny depth-of-field so we will need more pictures taken to build up an extensive area of focus in the image and we will need the camera to shift the focus by small amounts so we can get some overlap in those tiny depth-of-field samples. Should we use a smaller aperture to create more depth-of-field in each frame we’d need few frames and a greater distance between shots to achieve the same final depth-of-field.

Focus Bracketing with Lumix cameras

These are three of the individual frames from the sequence -the first frame and the two last. On each I’ve used a red line to indicate the area of sharpness in the subject. The first frame shows where the camera was focused at the beginning of the sequence, the second from last frame shows the focused area closest to the camera and the last frame shows the focused area furthest from the camera.

The correct size of step we select for each task will be a matter of guess work, experience and trial and error. It is impossible to assign fixed measurements to these steps as they have to make sense for landscape photographers as well as macro workers.

Stacking software

Which software you use to stack your images is a matter of personal choice. I use Adobe Photoshop as that’s what I use most generally and it has enough control for the sorts of things I need to do. Helicon Focus is a dedicated focus stacking program that offers more controls and flexibility, and will suit more advanced users.

Uses

Although the challenges of depth-of-field in macro photography make close-up work an obvious target for focus bracketing and stacking, the technique is also useful in a wide range of other types of work. In landscapes we will be able to extend our depth-of-field from the foreground in to the distance without having to stop down to an aperture that will destroy our resolution, and in product photography it can help us get the whole object or collection of objects sharp when a smaller aperture can not. The same goes for architecture – inside and out-, still life and any type of situation in which the subject isn’t moving and you need an extensive depth-of-field. The built-in focus bracketing mode in some of these Lumix cameras just makes life that much easier and this advanced form of photography far more accessible.

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Member Comments

  1. kirsty posted a comment on 29 March 2019 at 5:09 pm

    That is a great tip

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