Focus Stacking
No, it is not a pile of focus.
A subject the macro guys and some landscape folks know a lot about is called focus stacking. You see, when you focus on a particular point in space the depth of field related to the physics of the camera and lens dictates that a certain distance in front of the focus point and a certain distance behind the focus point will appear to be in focus. Actually, there is only one truly “in focus” point which represents the plane parallel to the sensor at the point of focus. Enough technical stuff.
What this means is if you are trying to render a three dimensional subject in focus in your image, you need to understand what the depth of field is. There are numerous apps that help you do this. A popular one is DOF Master.
But, that isn’t my subject. This post describes a technique for getting all of the subject in the image in focus per your artistic desires. It is called Focus Stacking.
The technique requires several things to be successful: even light, a static subject, a good tripod, manual focus on the lens and manual mode for exposure. It also requires a software solution in post production.
So, as you decide to capture a subject and you have it composed with the camera and lens you think will do the best job, the first step is to see what kind of depth of field you have available. I will use an example of an orchid flowering in my garden. I want to shoot it from a distance of 4 feet with a full frame body, a 100mm lens and I would like to use f/8 for an aperture. Looking this up in the calculator shows me that I have about 2 1/2 inches of depth of field. Since the distance between the front and back of the orchid plant that I want in focus is 12 inches I would have to shoot around 8 images to get each part of the subject in focus. I have found it better to shoot more images and make sure the depth of field overlaps. So, in this case I would shoot 10-12 images.
Here is the technique. Set up the camera on a tripod, frame the subject and lock it down. Set the lens to manual focus. Set the f-stop to 8 and determine the shutter speed for the correct exposure. These settings will not change.
Next, manually focus on the nearest point on the subject. I like to put my hand in front of the lens and fire a shot to establish the beginning of the sequence. Then take 10-12 images moving the focus ring very slightly. When you see the back of the subject is in focus you are done. Click off another image with your hand in front of the lens to mark the end.
Next, we need to have a software solution that is going to align all the images and pick out the “in focus” elements in each image, combining them into a finished image. Photoshop will do this. There are several other stand alone solutions. I like one call Zerene Stacker.
My workflow is to import the images into Lightroom, apply a preset to all of them in a batch and export them as full res tiffs to a folder I call Focus Stacks. Fire up Zerene Stacker, drag the tiffs into the input window, click on the type of stacking you wish and let it do its thing. I then save the resulting tiff back into the Lightroom folder with the original images and import it into Lightroom. I then apply develop settings in Lightroom or, more probably, take it into photoshop where I clean it up, apply some NIK plugins to get the look I want and then send it back to Lightroom. From there, I might do a final crop and then send it to a collection for posting, emailing or printing.
The finished product:
