This tutorial will help make it much easier for you to take the photographs needed for focus stacking. This is the best and the easiest way to achieve the results you want. There are a few details along the way, but the bonus is that there are also other photographic situations where you will be able to apply the same technique.
What is focus stacking and why is it needed?
When your camera is really close to the subject, depth of field will be very shallow. For example, if you are using a 100mm lens, at a distance of 50cm (nearly 10 inches from your subject) with an aperture as small as f/16, the area which is acceptably sharp is just 1.9 cm (about 3/4 of an inch). Reduce the distance to subject to only 25cm (less than 5 inches) and the depth of field reduces to only 0.36 cm (1/6th of an inch).
The only way to conquer this issue in order to get a greater depth of acceptable sharpness in a final photograph is with computational photography. That means using software to blend together a number of photographs which have been taken with different points of focus. This computational process is called focus stacking.
Input
The recommendation made in this article is an application of the old computer acronym of GIGO. Garbage In, Garbage Out. If you input rubbish, the output will be rubbish. To achieve the best results with focus stacking, you need to produce the photographs which are technically the most suitable for the focus stacking process.
Processing
A while back, I decided that I wanted to make some images that would look good in a home or workplace, which would reflect the Filipino environment. With various adjustments, the five photographs shown in color above were combined to produce the image below (and a lot more like it!).
If you like the idea of producing something like this, with sharp focus through the whole frame, it needs a little attention to start. This soon becomes quite easy, and you may find that it is actually a lot of fun. Find your own subject, then follow along with this method for producing your focus stacking images.
The actual processing of the images is a sequence of steps, and I would be happy to go through my approach for you at another time. Although there are other specialist programs for producing a focus stacked image, you will most likely use Photoshop. Of course, there are tutorials on how to do this here on dPS; A Beginner’s Guide to Focus Stacking.
The Method – Part One – It is a Surprise
At this point in most focus stacking tutorials, you will see somebody holding a set of focusing rails. Forget it! No further expense is required here. They might then talk to you about focusing manually. Forget that too! No need for any delicate touch with this method. You do not even need a cable release. This is absolutely all you need.
In the past, I had not even bothered to install Canon’s software offerings. Yes, the surprise news might just be that it is Canon EOS Utility which will serve you best for shooting focus stacking images.
As far as I have been able to determine, Nikon users will find that Nikon Capture includes a Camera Control component. I do not have the facility to put that to the test, but I imagine it works just as well. If you shoot Nikon and give this a try, do tell us how it worked for you in the comments section below.
The magic trick – the secret sauce – the silver bullet, for making images for focus stacking is the Canon EOS Utility program. It allows total remote control of the settings of your camera when shooting tethered to your computer.
Plug and play!
Once you have your shot set up, you can control everything from your computer. If that happens to be an adjacent laptop, that will work the best. However, the photographs which follow below were produced with everything controlled from a computer in another room, fully 10 meters, more than 30 feet away from the set.
The Method – Part Two – The Mechanics
This type of photography, which I think of as “constructed photography”, does take a little while to set up. Follow these steps:
- Put your camera on a tripod.
- Compose your shot.
You need to make two measurements.
- Measure from the focal plane of the camera (the mark indicated above) to the front of the object which you are photographing (A), as shown above.
The circle with a line through it indicates the focus plane – this is where your lens focuses the image onto the sensor.
- Measure the depth of the object, from the point which is nearest to the camera, to the point farthest away. I have found that a steel rule or tape measure works well enough for these tasks.
Standard issue.
- Now take a test shot.
- Use a small aperture, like f/10, then check the exposure. I tend to look at the LCD screen which gives the RGB histograms. This allows you to judge the exposure, exposing to the right if you like, but also to check that none of the individual colour channels is overloaded. That is prone to happen in photographs which have one subject filling the major part of the screen. At this stage, exposure is not critical, you are only trying to achieve a guide shot.
- Make a note of the settings which have given a reasonable exposure.
- Cover the viewfinder to prevent possible light leakage.
- Switch off image stabilization, it is always the best practice to do so when your camera is on a tripod.
- It is not essential, but you might choose to put your camera into manual focus.
Manual focus, stabilizer off.
- Again, not essential, but you might choose to put your camera in Manual shooting mode.
Switch to Manual Mode
Now the magic begins, the bit which makes me smile at how brilliant and easy it is.
The Method – Part Three – Computing
Connect your camera to your personal computer using Wi-Fi, a USB or Ethernet cable, whatever works best for your setup. I like cables, so I use a USB cord.
Run the EOS Utility software. Your camera should be discovered quite easily.
The EOS Utility dashboard.
Choose “Remote shooting” and the screen below will appear.
You are in control
From the comfort of your computer, you can release the shutter, the ultimate cable release, and do pretty much whatever else you like. As advised, you can switch off autofocus, and switch to Manual Mode without even touching the camera. In fact, adjustments can be made to all the usual camera settings for shooting. Most importantly for this exercise, you can switch to Live View shooting. Do so, and you will see a screen like this.
The Remote Live View window. This is where the fine focusing happens.
The first thing to do is to fine tune the exposure. Controlling your camera from EOS Utility soon becomes quite easy, and intuitive. You can actually learn a lot about exposure by experimenting with the exposure triangle of ISO, shutter speed, and aperture all from your computer, with the benefit of Live View in grand scale.
One extra benefit of shooting in Live View is that you will have locked the mirror up, and removed any chance of vibrations from that source.
You can click on the screen arrows, even use the scroll wheel on your mouse to make adjustments.
Take a shot and it will soon appear on your screen. This is not an article on ETTR (Exposing To The Right), but there is a good one here; Exposing to the Right. You can now adjust the exposure to try and get as much data onto your sensor as possible (the premise of ETTR). Take your time and take as many shots as you like. Check the histogram, check what you can see on the screen, and get the exposure exactly to your liking.
I do tend to prefer a shorter exposure. In the interests of sharpness, if I can get a compromise between ISO, and aperture which gives me an exposure of less than 1-second, I believe that is a good step in the direction of sharper photographs.
For this particular exercise, there are all sorts of detailed decisions, but the most important part of this screen is the Focus Adjustment and the Zoom View.
Double clicking on the area highlighted, shown towards the bottom of the screen capture of the Remote Zoom View window (shown above), will bring you to this window below.
Zoom View – allow you to easily get the nearest point of the image sharp as possible.
You now have turbocharged, hyper control of your focus. Not until you take the plunge and try this method, and find out that you can focus to the width of a hair, will you realize how brilliant it is. There is even the facility to zoom in further still.
I believe you will find the focus adjustment intuitive. There are three different levels for adjusting focus in either direction, “<<< / << / <” and “> / >> / >>>”. This is very useful in a way that no focus rails or manual adjustment could ever be. The bonus is that you will have no physical contact with the camera whatsoever.
The Method – Part Four – Finally
Martin Bailey is a photographer who goes into admirable detail. He is of the opinion that if you start photographing to the rear of the object, and work forward, Photoshop handles the process better. I do not see the evidence so clearly but, experience tells me, he is very likely right.
Another piece of advice would be to shoot a little wider, do not frame as tightly as you might usually. It gives you a little more room for maneuvering if you need to make adjustments.
You now need a Depth of Field (DoF) calculator. There’s a wide choice, there are many that are readily available for your computer, phone, and for use online. I happen to use, Simple DoF (iOS only, see Android options here), as shown in the screenshots. Let’s apply it to a situation.
The depth of field required for this scene is about 20cm (8 inches) To determine what you need, measure from the part of the object nearest the camera to the point furthest away. Divide that by the Depth of Field of 3.39cm (let’s call it 3.4cm), which tells us we will need 5.88 images. That means that we will need to take six evenly spaced images from the back to the front, in order to get every part of the image in focus. Here they are!
Focused at the rear, on the plastic case of the ruler.
Moving forward, picking a point about 3cms (just over an inch) closer each time.
Focused between 6 and 7 inches.
Shot 4.
Coming forward.
Focus closer 3cm, about an 1 inch, each time.
Finally, focused sharply on the front edge of the ruler.
You can go to whatever lengths of precision you like. Experience allows me to trust my judgment of distance, and I am happy to err on the side of taking too many shots. If I reached the front edge of the saucer and found that I had taken eight shots I would be perfectly happy with that. As it happens, it seems that I took seven.
Here is the image produced from all the above by following the focus stacking processing routine in Photoshop.
The final focus stacked image.
You should always be looking for ways to improve. As I have said, better results from less effort is a good thing.
Next
I think that to be certain of producing the highest quality product, the next time I do a project like this, I would refine my technique a little further.
I would actually put a rule next to the object but, unlike this time, do so temporarily. In this specific example, I would decide to take 3cm as my Depth of Field. I would then focus a shot on the 0cm mark of the ruler. I would then use the focus controls in EOS Utility to nudge the focus to 3cm and see how many clicks of the “>”, “>>” or “>>>” buttons it took to move the point of focus 3cm. It might, for example, be three clicks of the “>>>” button. Again, sticking with this example, I would then know that I needed to take seven shots. I would then take a shot focused on the back edge, click “>>>” three times, take another shot, click “>>>” three times again … and so on. As I said at the start, what could be easier?
Summary
This leaf was 10cm, that is 4 inches from front to rear. I do not think there is a way to produce this final image without using the technique of focus stacking. What you have read above is the best, and the easiest way to produce the shots.
Waving goodbye?
I am all for spontaneous, shooting on the run, shots. However, if you want to shoot in a more controlled way, I think you might find the control offered by Canon EOS Utility to be a lot of fun. I do!
Once you have been introduced to it and learn some of the power of the software, you may well find yourself using it for other projects. This last week, I have used Canon’s EOS Utility to produce some product shots. The proof is in using it, and I hope you can see that it is something you can try if you want to do focus stacking.
The post How to Photograph the Images Needed For Focus Stacking by Richard Messsenger appeared first on Digital Photography School.
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