I was trying focus stack using android app from my Nexus 7 Tablet. There are several camera controlling software in the Android play store. DSLR Camera Pro, Helicon Remote, DSLR Remote, DSLR Remote Controller, DSLR Controller, DslrDashboard are few such apps. DSLR Controller and DslrDashboard are my favorite in this list. To be able to use these application with your USB connected DSLR you will need an Android device that supports the USB host function and an USB OTG adapter. I used my Canon EOS 5D Mark III with Canon EF 100mm f/2.8L Macro IS USM illuminated by Canon MT-24EX macro twin light flash for this shoot. I connected my nexus 7 tablet with and OTG adapter & and USB cable to the camera. Most of these apps allow you to completely control the camera including focus points, all the camera as well exposure settings.
Focus stacking is a powerful technique for extending a photo’s apparent depth of field. It’s perhaps most useful in close-up and macro photography, since the camera lens’s highest f-stop is often insufficient to render everything in focus. It can even overcome the otherwise unavoidable sharpness loss from diffraction. When a photographer requires more depth of field, they typically just increase the f-stop setting of their camera lens. While this is a simple and effective technique, choosing a higher f-stop also has its disadvantages. It increases the necessary exposure time, and in extreme cases, it can also reduce image sharpness due to diffraction. Furthermore, one might desire a greater depth of field than a particular lens’s maximum f-stop is able to provide. Focus stacking can be done in two ways. Using micro-focusing rail on a tripod and slowly bringing the camera towards or away from the subject is one method. Fine micro focusing over different parts of the subject, starting from one end of desired focus to another end is the second method. Apps use the latter method in much more controlled fashion as they can control the micro focus much better than human finer can do.
For this experiment, I took help of my friendly neighborhood Two-Tailed Spider in my car garage. It is constantly sitting there without moving, waiting for insects, spreading its irregular silk over the nearby area. When a small insect disturbs the silk and the spider senses this and will quickly run around the insect in circles, with the insect in the center. The spider will also lay more silk at the same time, until the insect is entangled in it. This is a Long-spinnered Bark Spider, Hersilia species also known as two-tailed spider belonging Hersiliidae family. You can learn all about this spider in my earlier blog – .
Once I placed the camera on my sturdy Sirui M-3204 Carbon Fiber Tripod and secured it, I connected my nexus tablet to the USB cable via an OTG adapter. I had to make sure that the lens I was using was in auto focus mode and not on manual focus mode. I fired the DSLR Controller from the nexus it found my camera and went I to the option of focus stacking from the menu. Most other apps also the procedure is similar. It asks for number of steps and how big the steps are. Once you feed in the steps, you can start shooting right from the application itself without touching the camera. I chose 5 photos with small increments of focus for each of these 4 photos posted here.
Once all the photos were captured, I loaded them to my PC and went to Lightroom where I exported each photo as tiff file to a folder. Then I used my favorite stacking program Zerene Stacker to stack these 5 images each using PMax stack all method. Since the spider was not moving at all during the shoot and my camera was perfectly stable, there was no need to perform any retouching. I imported the file back into Lightroom and then precessed it slightly and exported as Jpeg.
Focus stacking is an amazingly powerful technique, but it definitely has disadvantages. It can be very time-consuming and it usually requires the subject matter to be motionless. It may require a precision focusing device (such as a focusing rail) or a software alternative like these software. It surely requires specialized software to align and merge/blend the photos like Zerene Stacker.