A day off work and I was looking for something to do around the house, because, well COVID. I decided to take my camera out into the garden and have a play around with the D850 focus shift shooting functionality.
For those of you who don’t know what focus shift shooting or focus stacking is, it’s a process where you take multiple images of the same scene focusing at different points in the image. These images are then stacked together in software to ensure the entire image is as sharp as possible. This process is used to to work around the optical limitations of cameras and lenses. It would normally be impossible to get things close to the camera and things in the distance all perfectly sharp due to the available depth of field. If you want to know more about depth of field and why this technique is useful, photography life have a good article on the subject.
While I’ve not been able to get out shooting much due to the COVID restrictions, I’ve tried to put my spare time to effective use by learning some of the functionality of the D850 that I’m not familiar with. One of these features is the D850 focus shift shooting. Another function that interests me is time-lapse shooting, but that is another article.
I haven’t previously bothered with focus stacking or felt it necessary. As you know, I did use a crop sensor camera until recently. I was quite happy with the front to back sharpness of the images I was capturing. Since upgrading to a full frame camera and being more deliberate with my landscape compositions, trying including foreground objects close to the camera, I feel the need to improve the front to back sharpness of my images.
At this point, let me say that you don’t need a D850 to do focus shift shooting. You can do it with any camera capable of manually focusing on a given point in the image frame. The D850 however will do this automatically based on a handful of menu options you can configure.
The menu option to access the D850 focus shift shooting options is located the photo shooting menu. When you select this option, you’ll be presented with some further configurable options as well as the option to start shooting.
- Number of Shots: This should be self-explanatory. The D850 can take anywhere between 1 and 300 shots in a single sequence.
- Focus step width: This option determines the amount the focus “shifts” between shots. The options are between 1 and 10. 1 being a smaller shift and 10 being a larger shift. What you choose here will be dependent on your scene. For closeup work you will need to use a smaller number and for a landscape shot a larger number will work fine.
- Interval until next shot: I’m not sur why this option is there. You can add a delay between shots if required, although I’m not sure why you would do this for focus stacking. Left at 00, the sequence will be shot at about 5 frames per second in normal modes. If you choose one of the Q modes, it drops to 3 frames per second.
- Exposure smoothing: Turn this on and the camera will automatically adjust the exposure of each shot to match the previous shot.
- Silent photography: If this is turned on, the shots are taken using the electronic shutter. You will hear the mirror lift at the start of the sequence and drop again at the end of the sequence.
- Starting storage folder: Choose this option to store all images from a focus shift sequence in a separate folder. This setting also gives you the option to renumber the image files, starting at 001 for the sequence.
Once you’ve changed the settings above to match your requirements, choose start shooting. The camera will then begin taking the sequence of images.
My First Attempt
The featured image at the top of the page was one of my first attempts at this technique. I took three sequences of images using different settings. The conditions weren’t ideal as there was light breeze moving the subject around slightly during the sequence of shots. As you can see, this has resulted in a couple of areas that aren’t completely in focus.
My first sequence was 50 images, with 2-step focus-shift. The second sequence was 100 images with a 3-step focus-shift and the final sequence was 100 images with a 1-step focus-shift. If you were to guess, which sequence do you think the final image above was created from?
You may be surprised to learn the above image was the result of the first sequence. I did also create a final image from the other two sequences, but there was no noticeable improvement.
Full Settings for the image above
The image was shot with a Sigma 105mm f2.8 macro lens at f8. The subject was roughly 30cm from the image sensor of the camera and it was 2 cm in size.
- No of shots: 50
- Focus step width: 2
- Interval until next shot: 0″
- Exposure smoothing: On
- Silent Photography: On
- Starting storage folder: New Folder
- Reset file numbering: On
The image sequence was stacked using Photoshop CC. Each image was loaded as a layer, then auto aligned, and auto blended. The resulting image was then flattened and exported as a .tiff file. I then imported the .tiff file in to lightroom and did some final adjustments to highlights and shadows, texture, and a radial filter to darken down the background.
A word of warning about processing. As you may or may not know, the D850 spits out raw files that are huge. Uncompressed they are around 95Mb each. With lossless compressing, they reduce to around 45Mb. If you do the math, you can clearly see the problem here. A stack of 50 images is 2.5Gb in size. The PC I used for photo editing has and AMD Ryzen 5 processor and 16Gb of RAM. Loading the 50 images as layers into Photoshop took just over 30 minutes. RAM usage by photoshop peaked at around 12Gb.
What I’m trying to say is just be patient, don’t expect this to be an instant process. Likewise, auto alignment and auto blending will not be as quick as you’re used to with a smaller number of layers. Click the menu option and go make a coffee.
If you’re not familiar with how to do focus stacking in photoshop, there are plenty of tutorials out there. I may write a separate article, but I don’t feel the need to re-invent the wheel. The tutorial I watched to get started was this one by Nick Page.
A word about Focus Breathing
If you don’t know what focus breathing is, it is when the focal length appears to change when the focus distance changes. This means that if you focus close to the camera and take an image, then focus on infinity and take another shot, the field of view in the two images will be different. This is a very basic description of focus breathing. If you want to delve deeper into the subject, try this article from Photography Life.
This causes problems when you align and stack the images in software. It can leave the edges of your frame out of focus. This is because the edges of the frame are often in the distance but are only included in the wider image view that was shot at a closer focus distance. This issue is rarely mentioned in any of the focus stacking tutorials I’ve read or watched. For now, I simply shoot a little wider than I need and crop the out of focus edges of the final image. If I find a better solution, I’ll post a follow up article.
If you’ve wondered how macro photographers get such great images with amazing depth of field. Or how great landscape photographers get wide vistas perfectly sharp front to back, focus stacking is the answer.
It takes time, and some practice like most things. I’m amazed at the results from my first attempts and will definitely be trying to incorporate this technique in to more of my landscape and nature images. I still have a lot to learn, but it’s a technique that can take images to the next level. Well worth spending some time experimenting with and perfecting.
As always, thanks for taking the time to read this. I hope you found it useful. If you want to ask any questions or have any suggestions on how I can improve my technique then please drop me a line in the comments below.
Have a good one.