An Introduction to Focus Stacking

A guest post by Chen Wei Li from www.bythewei.com.

After weeks of preparation, I finally set out to the Singapore Botanical Gardens to nail the shot above using the technique called focus stacking.

Focus stacking is a technique used to increase depth of field in a shot with post production. This works especially well for shots using long lens and in this case, a macro lens. Let’s go back to some photography 101 here. There are three factors that will affect depth of field or ‘bokeh’:

1. Focal length. Essentially the longer your lens, the more shallow your depth of field is.

2. Distance to subject. The nearer you are to your subject, the shallower your depth of field is and it very much applies to macro lens.

3. Aperture settings. The more you open up the aperture of your lens, the resulting image has a shallower depth of field. This, however, does not matter as much where the photo above is concerned.

I am happy to say that the experiment above has been a great success!

A little more background story.

It all began on 15 May 2010, when i was making my usual walk around the Singapore Botanical Gardens to take photos. I spotted this interesting looking cactus and ran a few shots at it. When i came home and uploaded the photos, below what was i got:

I’m pretty pleased with the composition and stuff. But i hated the shallow depth of field and the resulting ‘bokeh’. Some might argue it helps to lead viewers eye to the core but i believe the cactus lines have done enough a job in that department (Go find out more on leading lines for composition if you are not sure what i am talking about). I wanted other parts of the photoraph to be focused as well.

I told myself surely i had to come back again to work on the same shot… But how?

Thankfully, i remembered a friend of mine who once mentioned the use of focus stacking for food photography.

So exactly how does focus stacking work you may ask. Well, focus stacking simply means taking multiple photos of the same subject, each with a different focused spot. This is followed by the use post-processing software like Adobe Photoshop CS4 to align the focused portion of each image into one final-and-focused image. It is a really simple technique that everyone can use on their photos.

In the mean time, here’s what I needed:

1. A very very very very steady tripod. I’m not referring to those free tripods that comes with your DSLR purchase. Technically it works but i can bet a million bucks these tripods will give you hell before anything else. In my case i used a Manfrotto 055XPROB and Manfrotto 410 junior gear head. Both are, in my honest opinion, a very hardcore combination in terms of stability, durability and precision.

2. A macro lens. To achieve my desired composition, i had to go really close. This means that even if i am shooting at f/8, the depth of field remains shallow. Not to say that other lens won’t work but you probably will have to crop the shot and risk losing overall image quality. In my case, I was using a Canon EF 50mm f/2.5 compact macro paired with a LED ring light (not particularly useful on a sunny day though)

3. Super precision matt focusing screen for manual focusing. Locking your camera on a tripod means you cannot move the camera (duh) and rely on your in-camera focus points to focus different parts of the image. Here, i used a Canon Es-S focusing screen and paired it with my 5D Classic. Awesome screen for manual focusing may i add.

4. A lot of patience. I spent no less than 30 minutes under the sun (where the cactus was conveniently situated at the time of the day) just to get the composition, the tripod positioning and lighting right.

5. Last but not least, you need a proper post processing software to handle focus stacking. Thankfully, Adobe CS4 has that feature

Ok moving on to the shooting part of focus stacking. The shot you see about actually consist of four different shots aligned and merged into one single shot, thanks to Adobe Photoshop CS4.

Now let’s look at the four photos, notice how each of them is focusing at a different spot:

Hopefully by now, you get the drift. Basically i’m taking the focused part of each photo and merging into one sharp and focus shot.

Now with the four photos, here’s what you need to do with CS4:

1. Create one file with all four layers stacked on each of in a linear arrangement. This means that you SHOULD NOT jumble up the sequence of focused image.
2. Select all four layers, go to Edit>Auto align layers.
3. Once the layers are aligned, go to Edit>Auto blend layers.
4. Let’s the software run some processing and you will get an image with the sides slightly out of focused. This is caused by auto-alignment and auto-blending.
5. Crop the image to get rid of the out of focused areas.

See! It’s that simple.

Do go out and have some fun with focus stacking. Remember, a sturdy tripod really helps to make life easier here 🙂

PS: I stumbled upon this online discussion where people are calling focusing stacking the new HDR. Technically, they are right. HDR requires taking several bracketed shots and merged them into one shot while focus stacking required several (and differently) focused shots of the same subject and merge into one. Some of them also correctly pointed out that people are going overuse this technique just like HDR. Well, let’s just leave this topic for another day shall we?

About the Author: Chen Wei Li is a freelance photographer based in Singapore and is nominated for the Top Photography Blogger in Singapore Award. His portfolio can be viewed at www.bythewei.com. He can also be found on Twitter as @bythewei