"Here's a new guest blogger for this website: Mike Aronson (my Dad). He has a technical background in engineering and he shares our passion for photography. In today's post, Mike will share his 'lessons learned' with macro focus stacking. This is a specialized technique for those that want super-sharp (front-to-back) close-up images."
Focus stacking is a way to obtain a close-up (macro) photo of an object where the entire object, not just part of it, is in perfect focus. Typically one uses a macro telephoto lens, extension tubes or a close-up add-on lens to take these shots. As a result the depth of field is very narrow, and the object is only in focus at one place. Focus stacking solves the problem if narrow field of view.
HOW IT WORKS
A series of photos are taken starting with the front (closest) part of the object in focus. Then the focus point is moved slightly toward the back of the object and another photo is taken. This process is repeated until the last photo has the back (furthest part) of the object in focus. Then all photos are post-processed to first align them, then combine only the in-focus parts of each photos. The resulting single image will be collage of pieces of each original photos. The object photographed will be sharp and clean, while preserving the bokeh of the background. This magic happens quickly and easily. I use Adobe Lightroom and Photoshop; however, there are other software programs that do the same thing (e.g., Zeren Stacker). This process works on both JPEGs and RAW files.
WHAT DO YOU NEED
A good sturdy tripod, a camera with manual focus and a somewhat telephoto lens (many articles suggest a 100 mm 35 mm equivalent lens), and a means to focus close to the object of interest (flower, bug, coin, etc.). A macro lens is great but expensive. Extension tubes are inexpensive but tend to cut down on the available light. A close-up lens is attached to your telephoto lens and does the job nicely. An inexpensive close-up lens that I use is the Raynox DCR-250 Super Macro Snap-On Lens ($71.99 at Amazon.com). As the name indicates, it comes with a convenient snap-on adapter to fit any lens filter from 52 mm to 67 mm. As explained later, another very useful tool is a focusing rail. This is an attachment that one attaches to the top of the tripod, then attaches the camera to the top of the focusing rail. Rack-and-pinion like knobs allow the camera to be moved closer to, or further from, the object being photographed in very small increments. An inexpensive, but good product is the Neewer Pro 4 Way Nacro Focusing Rail Slider ($45.31 at Amazon.com).
Put the camera in manual focus mode. Some articles say to turn off optical image stabilization due to the use of a tripod. My tripod exhibited some vibration from touching the camera or walking near it on a patio, so next time a may leave OIS on (this time it was off). The first step is to frame the object being photographed the way you want, then focus only on the nearest edge to you for the first shot. I used a Fuji X-E2 with an 18 – 55 mm lens at maximum zoom (84 mm 35 mm equivalent). As soon as you turn the focusing ring, the camera enlarges the image greatly to help focus. Unfortunately the area magnified is in the center of the field-of-view, not the front edge. So the way I focused was to pragmatic – move the tripod until the front of the object is pretty much in focus, then fine tune the focus with the adjustment knob on the focusing rail. I set the camera to delay the shutter for 2 seconds after the shutter button was pressed to minimize camera vibration. In the future I will use a remote shutter release to further minimize vibration. After the first photo, I turned the focusing rail adjustment knob a small amount and took the second photo. Don’t fiddle with manual focus at this point. Moving the camera will put a small area a bit further from the camera in focus. Repeat this until photos have been taken from front to back of the object. I found that eight photos worked fine. Those desiring perfection may use up to 30 photos (but expect long post-processing time).
Note: you may need an external source of light if you are taking the macro photos indoors or on a cloudy day outside.
For me this occurs in two steps: first in Adobe Lightroom and then Adobe Photoshop.
Import the sequence of photos you took of an object. If, for some reason, the camera was moved and a photo is way different than the others, you may want to omit it from the processing. But don’t give up on minor variations from photo to photo, the software can fix many such issues. Choose a representative shot, use Lightroom to fix the color temperature, contrast, clarity, sharpening, etc. the way you want it. Highlight all photos, right click on the photo you edited and choose “Settings/Copy Settings”. All photos will have the same editing adjustments. Note that as an alternative I think you can do the Lightroom adjustments to the final product at the end of the post-processing.
Next (with all images highlighted) choose from the menu “Photo/Edit In/ Open as Layers in Photoshop”.
Photoshop will open and load each of your images as a separate layer. This could take several minutes. The process is simple but there is a lot of number crunching going on, so be patient.
Highlight all layers. From the main menu select “Auto Align Layers”. Photoshop magically aligns the content of the photos and compensates for slight variations. Then from the menu select “Edit/Autoblend Layers”. A pop-up will give you some choices. Choose “Stack Images” and be sure that “Seamless Tones and Colors” is checked, then click on OK.
At this point you can collapse the layers (“Layer/Merge Layers”) and do any Photoshop editing that is necessary on the single remaining layer. For example, there may be shadow-like artifacts where it was not possible to perfectly align some of the photos. For example this could easily happen if the wind was blowing a flower. When done, do a Save and Close.
BACK TO LIGHTROOM
The composite TIF file will show up in Lightroom with the file annotated as “edit”. It will also be larger than your other original files. You can do any final editing of the image, then export it as a JPEG to show friends or post you artwork on social media.
Here is an example of what focus stacking can do. I used an artificial decorative plant as the object and focused on a small part of it. Figure 1 is the first of eight macro photos showing the narrow field of view. Only the closest part of the artificial plant is in focus. After processing eight photos as described above, Figure 2 shows the final result of the focus stacking.
Have fun and try it – it takes a little patience and effort but can result in some terrific images. The first shot is just a regular close up shot...the 2nd image is that same image done with macro focus stacking.