• Ben

Focus Stacking - is it easy?

Focus stacking can seem like a daunting concept, and i have found that a lot of online content is quite unhelpful in getting started with it. Most importantly, there are different scales of focus stacking - let me explain...

1) studio high magnification stacking - all variables are fixed, camera movements are controlled by mechanical rails, and specialist software stacks many hundreds of images to create super high resolution images of tiny subjects. This is the most specialist and expensive type of stacking.

2) handheld or tripod mounted live focus stacking of maybe 20 images where there is a degree of control over the stability of the subject/camera. This is perhaps the most difficult type of stacking, and often requires a lot of manual editing work on the computer to get top quality results.

3) handheld, almost incidental stacking of between 2 and 5 images to improve on a single image. This approach is not terribly difficult, and can deliver the most realistic and satisfying results.

I'm going to explain the third type of stacking in some detail. This is my experience, you may have a different way, or a better way, but this is just a blog about my experience from a lot of trial and error.

First off, most online tutorials will tell you that focus stacking is easy, all you do is take 20 or so images, hit auto-align and then auto-stack in photoshop and hey presto. In almost every tutorial, I see these horrible artefacts in the images that the author will blindly ignore and say it was a success. At first glance this stacked image of a butterfly looks OK, but if you look carefully there are awful patches of it that are out of focus and misaligned - because the subject moved a little between images, and photoshop cannot account for that.

Photoshop's attempt at auto-align and auto-stack

Manually stacked version of the image. Not perfect, but far less messy around the edges. This was done from 18 images, and was quite a laborious task - the antennae alone are made up of 10 images. I stacked each antenna separately to overcome the fact that they move independently between images

The simplest way of successfully stacking images is to do it manually from a handful of images - sometimes only 2 are necessary. The example I will use to demonstrate this uses only 2 images.

In this instance, I was trying to get low to the ground to get exactly side on to this damselfly, but it was impossible, and the breeze was moving his perch around. The background was quite cluttered, so I had to use a wide aperture to get any kind of separation. I always have my camera set on high speed burst mode for macro, and instead of taking a picture, I will usually fire off a burst of 3 to 5 images each time - the beauty of digital photography!

When I said this type of stacking was sometimes incidental, it is often not apparent until the images are on the computer that two or more may fit together to create a single sharp shot. In this case, the movement of the grass had given me two consecutive shots, one with the subject's head sharp, and one with his tail sharp. The key is to just take lots of photos!

Head sharp, tail out of focus

Tail sharp, head out of focus

If I try to align these automatically in photoshop, it will try to align everything, the background, the grass, the head, the tail, all of which moved between shots.

In the video below, I show how to do it manually, accurately and easily.

(apologies if the audio only works on the left channel - my screen recorder is pretty basic)

The final image, sharp from head to tail.

The vast majority of my stacked images are done this way, from between two and five images usually. Doing this can mean the difference between shooting at f2.8 and f11 - four stops of extra light, four stops worth of clutter removed from the background, and four stops faster shutter speed!

The technique for larger stacks is exactly the same, it just takes longer to produce the final image. With insects, a lot of the time the body of the insect will only need two or three images (sometimes one!), but it might be necessary to stack a dozen images to have completely sharp antennae - so when I say a 14 image stack, 12 of them might be making up 5% of the image!

It is worth bearing in mind that the final image should also look realistic. The fact is that at the scale of an insect, an infinite depth of field is not natural. Some parts of the image really should be out of focus, knowing where to start and stop stacking is also important. As with any wildlife, connection with sharply focused eyes is important.

Another point I might also add is that several camera manufacturers advertise auto stacking in-camera - which is great. The camera automatically shifts the focus point by a fraction between shots and then combines them. This can be very successful, but in exactly the same way as outlined above, if the subject is moving, the results will not be great (it is effectively doing the same as Photoshop's auto-align and auto-stack). Don't be fooled into thinking that buying fancy gear will make the impossible somehow possible.

In summary - take lots of photos, and don't be put off by how complex stacking can be - the most successful images often come from two or three photographs.

Just to reiterate - this is my approach, and my examples - I'm sure many people have different and better solutions - but one of the things that attracts me to macro photography is problem solving and the creative process. It's not just about dialling in some predetermined settings and pressing the shutter - every photograph demands a unique solution - and the subjects are rarely still for long enough to let you think it through!!

Finally, here's a quick super sped up video of a full stack of 12 images to make a single image. I began with 18 photos, discarded 6 (either they were effectively duplicates of adjacent layers, or not required at the far focus end of the stack). The antennae accounted for 8 of the images, and the body and legs a further 4.

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