In the 70’s popular TV series Fantasy Island the opening always starts with a midget saying “The plane boss, the plane”.
Well, if you are a photographer the plane is the boss, whether or not you are a midget.
But this is not about airplanes. I’m talking about focal planes. And focus stacking.
One of the least used techniques in photography, probably, is that of focus stacking. Certainly, I don’t use it often and in most cases the technique is not even needed.
So, what is it and why it is something worth doing sometimes?
Focus stacking is a technique where a number of images are overlaid to produce just one image where there are sharp focus areas in places where it is not possible with just one image.
For the majority of landscape images, especially for wide angled shots, focus stacking is just not needed since there is plenty of depth of field already because of the nature of wide angled lenses.
However, when you are dealing with close-up shots and the depth of field is shallow, it may not be possible to get all the things you want to have good or acceptable focus with just one shot.
To get the final shot (image 3) below it was necessary to get good focus on the bees to the left as well as bees to the right.
But before you can shoot a composition like this you need to know a few things:
- Focus point vs focal plane
- Stopping down vs raising ISO
- Focus breathing
- Image scaling
- A focus point is of course just where the camera focuses in an image. The focal plane, however is everything that is in focus along a two dimensional plane. For example, if you were looking straight-on at a wall and you lock your camera to focus in the centre of that wall, then everything that is hanging on the wall will be captured as being in focus. However, if you rotate that wall say 30 degrees to the left or right, then only things that are directly above or below your centre point will be in focus.
- One way to achieve more focus on all the bees is to stop down the aperture so say f22 so that they will appear to be acceptably in focus. The problems, however, are two fold. First, at f22 you are going to get some pretty ugly background blur or at least very unpleasant bokeh. The second problem is that bees are moving quite fast and if you want to have them looking sharp you need a fast shutter speed. That’s why the images were shot at a higher ISO (to keep a fast shutter speed) and reasonably large aperture to keep a nice smooth background.
- Focus breathing is where a lens changes the image frame as you focus in or out. For example, if you have two people in the frame and you focus on one person and then change focus to the other, the position of one person in the frame will move slightly. This is normally only a problem in movies where when the focus in a scene changes from one person to the other it doesn’t look so good if the framing changes. Some people complain about focus breathing in camera lenses but there are no perfect lenses. Just about every lens designed for photography has this problem.
- Because lenses suffer from number 3 above, when you stack multiple images you can’t just brush in or brush out elements in the images. You must first scale the images so that they all line up nicely on top of each other.
- Brushing in or out is the easiest and final part. In Photoshop you just set the opacity so that you can see the layers above and below. Usually, this is around 30%.
And these are the camera details of the shots:
- D800 with 200mm f4 AIS. The 200mm f4 is a superb but really cheap lens. You can get one for around 120€.
- f11 and 1/640 sec, ISO 1600. You need a high shutter speed to “freeze” the bees in flight. Usually, f11 is considered to be a very small aperture but at 200mm and close shooting the background will be plenty smooth.
Bees in focus on the left side. You will note that the plane of focus is all the bees on the left side plus the ones going into their house. The bees to the right are out of focus since they are not on the same focal plane.
Bees in focus on the right side plus a few in the middle. The ones in the middle are on the same focal plane as those on the right side.
All the bees are pretty much in focus.
You might think that this is all too hard but actually it is nothing compared to say learning the violin or something. This technique is fairly straight forward once you get the hang of it. The most important and difficult thing is really to know when and where to shoot these bees. This is something that you need us to help you with. We will be more than happy to help you out but you need to come.
Come to Bohinj!