The introduction of 4K video and photo features to mirrorless cameras has been a welcome addition. These features are more than just a marketing gimmick, helping you capture those unique moments that were sometimes too difficult or nearly impossible to achieve. One of the most interesting 4K features that the Panasonic Lumix line of cameras has added is called Post Focus.
Post Focus basically allows you to capture a scene and, once completed, choose the area that you want to be in focus. When Post Focus is enabled you will not need to focus at any point in your scene. You just have to press and hold the shutter button and your scene will be scanned for all of the unique focus areas. The camera then captures all of the photos necessary, up to a blazing 30 frames per second, to create the 4K file. You can now choose the area of the scene you would like in focus by touching the LCD screen and saving the photo. Post Focus is a feature that works extremely well and is very easy and intuitive to use.
However, Post Focus can be used for something even more useful, especially for photographers who do a lot of macro photography. Post Focus can be used as a very effective tool for a technique called focus stacking. For those not familiar with focus stacking, you use software to stack (or layer) photos taken at different focus points of the subject and then blend them together into a new photo. You can decide how much depth of field you want in the photo. You can choose anywhere from minimal depth of field to an unlimited depth of field with absolutely everything in the photo in sharp focus.
To achieve the best focus stacking results from Post Focus, its beneficial to know a bit more about how the process works. When Post Focus is taking all required photos, it is creating an MP4 video file. This is the same MP4 video file created with all 4K photo and video features. Since 4K is recorded with a resolution of 8.3 megapixels, each photo you save from the MP4 video file will be 8.3 megapixels. The extracted photos will also be JPG files as shooting and capturing RAW files at 30 frames per second would require processing power that current cameras don't have. While creating a series of RAW images manually for focus stacking may produce higher image quality, there is also more room for error and the high quality 4K 8.3 megapixel JPGs produced allow for high quality prints if using good technique and lenses.
Before the methods of image extraction are introduced, there are a few more points to note in order to get the best possible results. When you enable Post Focus, a crop factor will happen as the 4K aspect ratio is slightly smaller than the micro 4/3 sensor. Your subject may not fit into the frame anymore. Keep this in mind as you compose your photo before enabling Post Focus. When choosing your shutter speed and ISO, choose settings appropriate for capturing a sharp image of your subject. When it comes to choosing your aperture, you have a couple of things to keep in mind. Since Post Focus captures every focus point of the scene, you don't need to use a small aperture, such as f16 (which would cause heavy diffraction on a micro 4/3 sensor). It is best to choose a sharper aperture such as f/2.8-4 depending on which lens you are using. The only caveat is that since using larger apertures produces smaller depth of field, you will end up with more photos in the 4K MP4 file to extract and focus stack. Since Post Focus is capturing at up to 30 frames per second, hand-holding is a viable option, however, I still recommend the use of a tripod wherever possible, especially for macro (1:1 or greater) work. It is difficult to make and assess accurate macro compositions handheld. The last piece of info to note is that you need to make sure your lens is able to focus close enough to the part of your subject closest to you. For example, if your lens can only focus as close as the middle of your subject, the closest part of your subject will be out of focus after the focus stack. You can use any lens appropriate for the situation you are shooting and this technique isn't limited to just macro lenses; I will sometimes use focus stacking with photos from telephoto lenses.
There are a few methods of extracting the images from a 4K MP4 file. The first is by previewing the photo on the camera, touching the LCD screen at each point you want in focus and then choosing to save each one as a JPG when prompted. This method is tedious and not as accurate as using computer software. The second method of extracting the images is to use a recent version of Photoshop. You can open an MP4 file and then render the video timeline by choosing the Photoshop image sequence option from the rendering menu. When extracting the images through Photoshop you have the option of extracting the images as JPG or TIF. Using the TIF file format will be beneficial should you wish to further edit the images as there will be no further image degradation. Once saved, you can open the extracted photos in PS and use the focus stacking feature via Photomerge. The third and probably most efficient and highest quality method of extracting the images is to use Helicon Focus, the software I use and highly recommend as it produces excellent results. The latest version of Helicon Focus has added support for directly opening MP4 files. It is incredibly easy to choose which images you want to include or exclude from the focus stack. Since Post Focus has captured every single part of your scene "in focus", there will most likely be images you will not want to include in the focus stack. Some of the images will be of focused areas much further behind your subject.
Post Focus is an invaluable tool for the creation of focus stacked images. It is perfect for when the situation doesn't necessitate or allow for manually taking all required images. Now that you know how Post Focus can be used for focus stacking macro subjects, try using it for focus stacking landscape scenes. Post Focus is a very capable tool that is useful in many photographic situations.