FOCUS STACKING

Dr. Manas Chakraborty, EFIAP, EFIP.

In search of sharp image, we already figured out sweet spot of the lens which helps you to get the image with clarity and side by side we also discussed the annoying issue of Lens breathing in our earlier discussion. Now we will try to find out the way that will result amazingly sharp image. Yes, we are going to explore Focus Stacking. Focus stacking is a powerful technique used in photography to create images with enhanced depth of field. In traditional photography, it can be challenging to get everything in the frame in focus, particularly in macro photography, where the depth of field is shallow. However, by combining multiple images, each with a different focus point, it is possible to create an image that is sharp from front to back.

What is Focus Stacking?

“Focus stacking is the process of taking multiple images of a subject, each with a different focus point, and combining them into a single image with an extended depth of field. This technique is particularly useful in macro photography, where the depth of field is to be kept shallow, and it is difficult to get everything in focus in a single shot. In focus stacking, you take multiple shots of the subject, each with a different focal point, then combining these images in post-processing software to create an image with greater depth of field. The resulting image will have more detail and appear sharper than a single image shot at a single focus point.

The main advantage of focus stacking is that it allows photographers to create images with a greater depth of field, without sacrificing image quality or clarity. Another benefit of focus stacking is that it can help to reduce noise in images. When taking a single shot with a shallow depth of field, a photographer may need to use a wide aperture, which can result in a blurry image. On the contrary if you try to increase depth of field by narrowing the aperture too much, your image may become unsharp and will lose the desired clarity by diffraction of the lens optics. By taking multiple shots with acceptable aperture, preferably at the sweet spot of the lens and blending them together, the final image will be sharper, less blurry with deeper depth of field with unmatched clarity.

Example 1: Macro Photography of a Flower

In this example, we can see a close-up photograph of a flower taken using a macro lens.

Without focus stacking, it would have been impossible to capture the entire flower in focus due to the shallow depth of field at such a close range. However, by taking multiple shots with slightly different focus points and blending them together in post-processing, the photographer has been able to create an image that is sharp from front to back, revealing the intricate details of the flower.

Example 2: Landscape Photography

While focus stacking is often associated with macro photography, it can also be used in other types of photography, such as landscape photography. In this example, we can see a landscape photograph that has been created using focus stacking. By taking multiple shots of the same scene with different focus points, the photographer has been able to achieve a greater depth of field that would have been impossible with a single shot, resulting in an image that is sharp from the foreground to the background.

Example 3: Product Photography

Product photography is another area where focus stacking can be extremely useful. In this example, we can see a photograph of a watch that has been created using focus stacking.

By taking multiple shots of the watch with different focus points, the photographer has been able to create an image that is sharp and detailed with the intricate design and features of the watch.

How to Create Focus Stacking Images

Creating a focus stacking image involves several steps:

1. Set up your camera on a tripod and compose your shot.
2. Determine the focus points that you will use for your shots. You can do this manually by adjusting the focus point on your lens, or you can use software to determine the focus points automatically. In modern digital camera you can get the option of focus stacking from the menu itself.
3. Take a series of shots, each with a different focus point, You can use manual focus or you can use autofocus to set the focus point for each shot.
4. Transfer the images to your computer and open them in post-processing software. There are many different software programs available for focus stacking, with some of the most popular being Helicon Focus, Zerene Stacker, and Adobe Photoshop. Helicon and Zerene software are dedicated for stacking and remote tethering of Focus Stacking.

Helicon Focus and Focus Stacking

The digital revolution of the last few years made professional photo hardware widely available and affordable. Now it’s the advanced technology that makes the difference. Plain single shots are bit by bit giving place to improved and more sophisticated technologies like HDR and Extended Depth of Field (EDoF).

Today it’s hard to imagine macro or micro photography without focus stacking technique. Professional photographers and enthusiasts seeking to keep up with the trend take advantage of focus stacking to create eye-catching images.

With focus stacking software you can make your usual camera render results that could not be achieved even with a classic tilt-shift lens. Take several shots at different focus distances instead of just one, and Helicon Focus will quickly and smartly combine the stack into a fully focused image.

Nowadays micro photography, close-ups, jewellery and product photography became truly dependent on focus stacking. But it does not matter what you shoot – landscapes or flowers, animals or still-life – Helicon Focus will make your images stand out. Watch the tutorials, read the articles and impress your colleagues and friends with your new photo achievements!

These programs use complex algorithms to blend the images together, selecting the sharpest areas from each shot and combining them into a single, fully-focused image.

5. Align the images. Use software to align the images so that they are perfectly lined up. This step is critical, as any misalignment can cause the final image to appear blurry.
6. Combine the images. Use software to combine the images, focusing on the parts of the image that are in focus in each shot. The software will create a single image with an extended depth of field.
7. Adjust the final image. Once the images are combined, you can make final adjustments to the image, such as adjusting the colour balance or sharpness or any other required post processing tools.

Gears Needed for Focus Stacking

To create focus stacking images, you will need.

A camera with a manual focus option. Modern camera with autofocus with supporting firmware in the menu also can do the job for you. You have to be very careful to take all the shots with same exposure.

Focus shift in Nikon camera, which automatically varies focus over a series of shots, is used to take photos that will later be combined using focus stacking to create a single image with increased depth of field. Before using focus shift, choose a focus mode of AF-S or AF-C and a release mode other than Self Shooting. As I personally use Nikon in more instances, siting the examples of Nikon gear.

Selecting Focus shift shooting displays the options below.

Start: Start shooting. The camera will change the focus distance by the selected amount with each shot. After completing all the settings, you will select the START option.

No. of shots: Choose the number of shots (maximum may be up to 300 depending on the camera body).

Focus step width: Choose the amount the focus distance changes with each shot. Because depth of field is reduced at short focus distances, we recommend choosing smaller focus steps and increasing the number of shots when photographing subjects close to the camera.

Interval until next shot: The time between shots, in seconds. Select 00 to take photos at up to about 5.5 fps. 

First-frame exposure lock: If on is selected, the camera will lock exposure for all images at the setting for the first frame.

Peaking stack image: If create is selected, the camera will employ focus peaking to create a black-and-white preview stack that can be used to check focus after shooting. 

Silent photography: Select On to silence the shutter during shooting. If you try to capture small insects, they may not like the shutter sound.

Starting storage folder: – Choose New folder to create a new folder for each new sequence, Reset file numbering to reset file numbering to 0001 when a new folder is created.

Start and press OK. Shooting starts after about 3 s. The display turns off and the camera takes photographs at the selected interval, starting at the focus distance selected at the start of shooting and progressing out toward infinity by the selected focus step distance with each shot. Shooting ends when the selected number of shots has been taken or focus reaches infinity. To end shooting before all shots have been taken, press the shutter-release button halfway or press the OK button between shots.

To prevent the loss of definition that can occur at smaller apertures, choose an aperture close with the sweet spot of the lens, certainly not more than f-8.

Before Shooting–Before beginning focus shift photography, take a test shot at current settings and view the results. To ensure that shooting is not interrupted, be sure the camera battery is fully charged. If in doubt, charge the battery before use or use an AC adapter and power connector (available separately).

During Shooting–During focus shift photography, the release mode indicator in the control panel will turn off and the memory card access lamp will flash. Regardless of the option selected for Custom Setting c3 (Power off delay) > Standby timer, the standby timer will not expire during shooting. Note that changing camera settings while focus shift photography is in progress may cause shooting to end. Shooting will end if focus is adjusted during shooting.

Peaking Stack Image–During playback, a P icon appears on photographs shot with Create selected for Peaking stack image, indicating that a focus stack preview can be displayed by pressing the i button and selecting Display peaking stack image. The areas displayed in white will be in focus when the pictures are stacked. Focus stack previews can only be viewed on the camera used to create them.

If you are using a flash, choose an interval longer than the time needed for the flash to charge. If the interval is too short, the flash may fire at less than the power needed for full exposure. Focus shift cannot be combined with some camera features, including movie recording, time-lapse movies, bracketing, the self-timer, long time-exposures (bulb or time photography), HDR (high dynamic range), multiple exposure, and interval timer photography. Note that because the shutter speed and time needed to record images may vary from one shot to the next, the time between the end of one interval and the beginning of the next may vary. If shooting cannot proceed at current settings (for example, if shutter speed is set to Bulb or Time), a warning will be displayed.

 A tripod to keep the camera steady.

Wired or remote shutter release device to avoid the camera shake.

Special tripod head with 2-dimensional rail, preferably motorised, to get the stacked image more accurately. This gear is not compulsory but if you have this one, you can do your job with professional fineness.

Post-processing software that is capable of aligning and combining images. There are both free and paid software to do this job. Adobe Photoshop and Helicon Focus are two popular options.

Tips for Success  

1. Set up your slider for the farthest shot first as this will be the limiting factor to your framing. Make sure you have a solid tripod and base for your subject. As you may end up with an exposure set that takes minutes to capture, any movement can ruin the resulting image.
2. Run at least two seconds between exposures, this gives time for the slider movement to settle down. If you plan to use flashes to light your subject you may need to increase this to allow for them to recycle.
3. Use the silent shutter or electronic curtain, if possible, this also reduces shake.
4. Set everything to manual, including white balance. Sometimes small shifts in white balance can cause issues when blending images.
5. Take more images than you think you need even if you don’t end up blending all of them. It can be very difficult to see what is in focus on your camera’s LCD even when using peaking or expanded focus.

Illustration of Focus Stacking 

To illustrate the process of focus stacking, let’s consider the following example suppose you want to take a photograph of a flower in your garden. You set up your camera on a tripod and compose your shot, adjusting the aperture either at the sweet spot of the lens or something at lower f number and shutter speed to get the desired exposure. However, when you look at the resulting image, you notice that only a small part of the flower is in focus. This is because the depth of field is shallow, and the camera can only focus on a small area of the subject.

To create a focus stacking image, you take a series of shots, each with a different focus point. You start by focusing on the front of the flower, taking a shot. You then adjust the focus point slightly and take another shot, focusing on the middle of the flower. You repeat this process, moving the focus point slightly each time, until you have a series of shots that cover the entire depth of the flower.

Then transfer all the images to your computer and open them in post-processing software of your choice. You use the software to align the images, ensuring that they are perfectly lined up. You then combine the images, focusing on the parts of the image that are in focus in each shot. The software creates a single image with an extended depth of field.

Focus stacking is an amazing technique that can help photographers to overcome the limitations of depth of field in their images. By taking multiple shots with different focus points and blending them together in post-processing, photographers can create images that are sharp and detailed from front to back. With the help of focus stacking, photographers can create breath-taking images and showcase the beauty and details of the world around us.