The next topic I wanted to cover is something that I think a tethering product like the CamRanger should really be able to help with and that topic is Focus Stacks.
Just as a brief description, these stacks essentially take many images (2 -over one hundred) with a shallow DOF and treats them as cross sections (the part that is in sharp focus here) of a subject and layers them on top of one another to create a final image with a much larger DOF but usually at a macro level. It can also be used for non-macro but there are less opportunities for it there. For this, CamRanger allows you to take multiple shots at different focal points to be used to create this stack.
As with HDR, this function worked well. You select the number of shots you want to take and the level of focal shift (small, medium or large changes in focus) and the rest is done automatically. Unlike earlier, my macro lens had no problems with the focal shifts. The one thing to keep in mind with this though is that the camera isn’t moving, only the focal point does. This is an important distinction since it means there is a change in the geometric proportions of each image as that focus shifts. Whereas if the camera was the thing moving, the proportions would stay the same and they would be true cross sections.
As a result, when you stack these, you will need to use the remove geometric distortion feature to line everything up correctly. I imagine there must me a limit to the number of images than can be corrected before it no longer looks correct. I used it on a 4 picture stack and it worked just fine. Ideally, you would want the camera on a rail that lets you move the whole camera assembly in small increments to correct for this. There is a motorized rail available from Cognisys called Stackshot that will do this automatically but I have not tried it out as it is a little expensive for me at this time ($550) and I don’t have much use for it at the moment. Or you could get a cheap manual one from Amazon for around $20.
Next time, I will discuss my experience taking a night shots with the CamRanger.