In this article I want to share a favorite technique of mine when doing close-up and/or macro photography of my go-to subject at the moment, flowers.
In order to do this you do NOT need a state of the art camera or lens but you do need a software that can process your focus bracketed frames, for this I am using Photoshop. When it comes to gear I assume that you have access to a tripod even though I guess you in theory can get away with a decent result without one.
For illumination I am using a light box so if you want to use this technique exactly as I describe it here you will of course need access to a light box – also referred to as ‘Lightpad’ – but it’s not a prerequisite for doing focus stacking at all.
What Is Focus Stacking and Why Use It
Focus stacking is a technique used to acquire a depth of field from front to back that is not possible to achieve shooting a single frame. This is especially useful when shooting close-up or macro when you want everything tack sharp, no matter what f-stop you dial in it’s simply physically impossible to get everything in focus with one frame, the depth of field is too shallow. And even if you could you would probably not want to shoot at f/22 or smaller simply because of lens diffraction, a physical phenomenon that soften the photo no matter what gear you use.
How Do I Set up My Camera
Since you shoot multiple frames and you do want a consistent exposure , you need to put your camera in Manual mode. In theory if the light is consistent – which it should be – you could use, say Aperture mode but in my experience the camera can and sooner or later will, meter differently depending on where you have your focus points in the frame giving you a set with different exposure values that will confuse Photoshop when you later merge your frames.
Like I mentioned in the previous section, you shoot multiple frames and you do want a consistent exposure , you therefore need to do your focus stacking under conditions where you have control over the environment i.e the light. In this example I’m using my light box for illumination in a modest studio where I have full control of the ambient light.
Why a Light Box and What Is It?
A light box – sometimes referred to as Lightpad – was originally intended for illuminating negatives back in the days of analog photography, when evaluating and accessing the results. Using a loupe you could easily pick your keepers when viewed illuminated by the light box. Modern light boxes uses LED light and comes in different sizes, mine is made by KAISER and measures 8×12 inches, this translates to 20×30 cm. I chose this size with the idea that it would be big enough to enable me to get a good composition with a flower roughly the size of a tennis ball, a large Carnation or Chrysanthemum for example.
So why use a light box ? A light box illuminates flowers beautifully, they become magically backlit, this is especially true for flowers with a high degree of translucency like the Arum below. Other flowers can be used too, like the Rose above, but you often need to lift the shadows mainly the stem in this case in post processing or use a secondary light source. Translucent flowers shine on a lightbox so this is what you mainly want to use if possible.
The Studio Setup
OK, now we are ready to start shooting, you have your gear setup similar to the sketch above and your favorite flower ready at hand. A quick note about the tripod before we start ….you do not need to use a tripod with a horizontal center column like the one above but it is to be preferred . Why ? To get the maximum depth of field the camera sensor should be parallel to the Lightbox and the subject, with an ordinary tripod – that I actually used for the shots in this article – there is no way you can do this because the tripod legs will prevent you from getting the camera in that position and you are forced to frame the shot with the camera at a slight upward angle to reach over the table.
Like I mentioned earlier you should shoot in an environment where you control the ambient light in order to get a consistent exposure, I have a dedicated room, my ‘studio’ but this, of course isn’t necessary but very nice to have.
ISO and File Format
To get the highest image quality possible you should use as low ISO settings as your camera will allow, nowadays on a modern camera it most likely is ISO 100. To get maximum control when editing your work you should shoot RAW, you would never ever want the camera do any editing by shooting JPEG, and as I’m sure you know you know, JPEG is a file format that compress the image and therefore degrades it.
To get identical exposures of our frames you should set your camera to Manual mode, since we are talking fairly long exposures you need a remote shutter release or, if you don’t have one, set the release mode to self-timer. When I use the self-timer I typically set it to five seconds in order to make sure any vibrations caused by me pressing the shutter dies down.
When it comes to metering I exclusively use Matrix mode, in my book this is by far superior to any other mode. While this is true the very bright light from the Lightbox will fool any camera trying to figure out the correct exposure, be prepared to dial in to + 4 EV or more, to get correct exposure of your subject.
To evaluate the exposure you should consult the histogram and highlight clipping warning screens on you LCD. One reason to use a Lightbox for illumination is that you get a very bright nice looking background, with this in mind don’t be alarmed if you clip the highlights as long as those highlights is the background and not the subject. The histogram can’t tell you what is clipped but the highlight clipping warning screen can, pay close attention to this before you start shooting your set. The best use for the histogram in this case is to make sure you don’t clip the shadows, make sure the histogram don’t hit the left wall.
How Many Frames Do I Need to Shoot?
Now we have our camera all set and the subject framed the way we want it, it’s time to actually start shooting and you probably ask yourself how many frames do I need ? The answer to this question is, it depends. Factors like, what depth does your subject have, how close are you to your subject, what aperture are you shooting at all come into play. Another way of putting it is, it depends on the depth of field you have. To answer the question how many frames you need you will have to start shooting, evaluate the shots on the LCD until you feel that the frames you have, blended together will render a photo tack sharp front to back.
Let’s take a real life example, the purple Arum at the top of this article. Without looking trough the viewfinder, I look at the flower with the naked eye in order to find out which part is closest to the camera. Knowing this I focus at that part and shoot the first frame. The next step is to evaluate the focus by looking at the LCD. In doing this I see that the part of the petal furthest away from the camera is soft, shooting my next frame I therefore focus at this part. I repeat the evaluating process and see that the stem is soft, shooting the third frame I therefore focus on the stem. I have now got three frames that blended together will render the whole flower in perfect focus.
The trick here is -when evaluating a frame- to pinpoint which areas are in focus, store this in your memory, shoot and evaluate until you have covered all areas of the flower. In other words, for each shot you take you need to store the areas that are in focus in you memory, if not you will end up with frames that you do not need.
When processing the RAW files you do this exactly as you normally would. Pick one frame in your set, edit it and when you are done, select all the files in your set and sync the settings. In this way you make sure that all your files have been processed in the exact same way.
The next step is to open your set as layers in Photoshop. In Photoshop, select all layers, from the ‘Edit’ menu chose ‘Auto-Align Layers’ leaving it at it’s default setting ‘Auto’ . When this process is done, go back to the ‘Edit’ menu and chose ‘Auto-Blend-Layers’ set to ‘Stack images’. When Photoshop is done you have a new merged layer with all the frames blended based on the areas in focus. This is the end result, a photo tack sharp front to back. Now when the blending has been done the underling layers is not needed and can be discarded.
My Photo Isn’t Perfect?
In a perfect world the process described above should render the perfect picture, this however, isn’t always the case and often it’s not you that made a mistake. My experience is that sometimes Photoshop struggle and render some distinct smaller areas very soft or even blurred. When this happens some retouching will be necessary, knowledge of the tools available is then crucial. You don’t need to be an expert – I’m not – because the imperfections often don’t cover large areas and can generally be touched up fairly easy.
Chrysanthemum is a good example of a flower that needs more light than a Lightbox can offer, it’s non-translucent nature simply requires use of a secondary light source.
If a large section of the photo is soft I’d say you failed to cover that area when shooting. Don’t let this discourage you, this technique isn’t easy and some practice before you get the perfect result is to be expected.
I hope you found this article inspiring, good luck!