Helicon Focus for basic focus stacking
Helicon Focus review – focus stacking
#1 Starting with lens focus stepping
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Keith has used Helicon Focus for several years to stack multiple images. The stacking allows for increased depth of field and is particularly useful for close-up and macro photography.
Stuck indoors, like many photographers (April 2020) he’s put together a series of short reviews looking at using the Helicon software in different ways.
This first part of the review looks a simply using focus stacking, including Helicon Focus for actual stacking. Part 2 looks at moving the camera and the Stackshot rail with Helicon Remote. Part 3 looks at photographing very small objects in detail.
All of Keith’s Macro related articles and reviews are listed in their own category in the dropdown menu to the right.
Depth of field
As your subject gets closer to the camera, the thickness of the depth of field (DOF) gets thinner, for any selected aperture. Whilst a thin DOF may look great for some creative purposes, if you’re photographing objects, it can become too small to show all you want.
The example I’ll use here is a small model car – actually brought as a present for me by my Grandmother in Alsace some time around 1970.
As you can see, it was well played with…
The photo above gives enough detail for a smallish web image, but zooming in shows that only the part of the image near my finger is sharp.
This is at f/7.1. I could reduce the aperture to say f/16 and get a larger DOF but I’d start losing detail through diffraction effects. This softness comes from fundamental aspects of how light behaves and can’t just be sharpened away (although sharpening software has come on tremendously – see my Sharpen AI review).
In this example I’m using a normal lens with autofocus – the Canon EF 50mm f/1.4 USM. It’s mounted on my Canon EOS RP mirrorless 26MP full frame camera.
The camera is mounted on a Manfrotto slide rail, but I’m not using that here other than setting the camera position. I’ll come back to camera movement in the next part.
Extension tubes get you closer
Since the EF50 F1.4 has a minimum focus distance of 45cm, I’m also using a 13mm extension tube.
Extension tubes allow many lenses to focus closer than normal, but at the cost of an increase in effective aperture. They also stop the lens focusing at infinity. When fitting one it’s always worth checking where the near and far points of focus have been moved to. Tubes can be stacked for increased magnification, but the depth of field will get increasingly thin.
When working close, remember that the lens focus distance shown (without tubes) is the distance from subject to sensor plane, not the front of the lens. Where’s the sensor plane? Its position is shown by that dark mark just below the ‘E’ of EOS in the photo above. It’s usually shown on cameras as a small circle with a line through it.
Stacking needs a set of photos with the plane of focus running from front to back (or vice-versa).
Whilst you can just step focus from near to far and take photos, it’s far easier (and more accurate) to get software to do this for you. I’m using Canon’s free EOS Utility software, but many other camera makers provide such software.
You can do focus stacking (with AF) using the Helicon Remote application. However, I’ll leave a look at that until part two where I’m mainly using it to move the camera, not the focus.
The camera is connected to my desktop Mac using a USB cable. This gives me an excellent live-view display and full control over camera settings. I generally prefer a wired connection for studio use, but outdoors or in busy environments a wireless connection is fine, and depending on camera/devices may let you control the camera from a phone or tablet.
The default view is with the lens wide open at f/1.4. As you can see, the usable depth of field is very thin.
Even going to f/8 shows distinct softness at the front and rear of the car.
Note the histogram in the lower RH corner – this is excellent for checking exposure and showing any clipped highlights.
The car is lit with two CFL flat panel lights, but LED lamps would be fine.
I’ve looked at various light sources for experimenting with such photography [see the ‘Lighting‘ category of articles/reviews] and have quite a lot of information about getting accurate colour for shots.
Any photos I take are saved directly to my computer.
Shooting stacks of images like this will quickly create a lot of files – think about what you’re going to do with them. I normally shoot RAW+JPEG. Whilst Helicon Focus will handle RAW files, it’s a lot quicker to experiment with just high quality JPEG files. It does mean you need to be a bit more careful with exposure and lighting. If you find you need the editing capabilities that RAW files give, then only shooting the set of RAW files once everything is set up OK is an option.
EOS Utility gives me control over the camera, although I have set the control dial on the camera to manual.
All the usual settings are there to adjust.
Just remember that if you set the camera to JPEG only mode, then when you next use it, it will still be set to JPEG only.
Yes, I have gone on a job the day after doing macro work, without realising the camera was still set to JPEG – this is one of those things you only tend to do once.
Fortunately the 50MP JPEGS from my Canon 5Ds were more than good enough for what I needed.
Manual mode is your friend when automating stuff like this. You simply don’t want the camera deciding what settings it feels are best for each shot of your stack. In this instance though, I’ve left auto white balance on. For optimum performance I’d set a custom white balance with a grey card to match the lighting. If you’ve never done this, see your camera manual.
In the top right you can see that I’ve selected MF for manual focus. Do this here rather than with any switch on the lens. This lets the software manually adjust lens focus, which is what we want for stacking.
At the bottom of the window you can see that focus stacking has been enabled.
Clicking on this lets you define the stacking parameters.
You need to decide the number of shots and how many microsteps the lens is to make between each shot.
After experimenting, I decided that good results came from a step of 3 or 4. The shots need their sharp zones (DOF) overlapping for the aperture you’ve chosen. Too few images in the stack can show up as a slight banding of sharpness.
Also, start with focusing the lens just in front of the closest part of the subject. The software will step focus away from this point.
For the number of shots, I just put in a large number (50) since the software will then step away from the start point until either the lens is at its limit or the number of shots is used up. Since I’ve got an extension tube on the lens, the far point is actually not far behind the back of the car.
Click the top RH shutter button in the software window to take the shots.
Stacking in Helicon Focus
Helicon Focus is supplied by HeliconSoft. I’ve got the ‘Pro’ version, since I use it for my work and with the stackshot rail. There are demo versions available. There are quite a few software packages that offer stacking – I’ve a short list to explore at the foot of this article.
The software offers a wide range of advanced features such as being able to stack RAW files and output as a single DNG file, along with animations and different adjustable methods of stacking.
I’ll cover some of these in the next article, but I use it for its rock solid performance and reliability with my equipment.
After some shots taken with EOS Utility, I have a folder of JPEG images of the car to load.
Take a moment to look at the top (near focus) and bottom (far) images.
Notice how the car is a slightly different size in the images. This is because when you change the focus of a lens like this, you are changing the actual focal length. It’s not something we normally consider in photography, but is sometimes known as ‘focus breathing’ and can be of concern to video folks…
Fortunately, Helicon Focus will take care of this, but it does mean that you have to pay a bit more care to composition when setting up a stack sequence.
Simply dropping the 16 files from my first set of images on the window loads them.
How to stack
There are three basic methods of stacking
The three methods differ in how they handle differences between the images, especially if there are overlapping near/far elements.
The methods also differ in whether they require consecutively (depth ordered) photos or can handle ones in any order.
This is from the excellent overview on the HeliconSoft web site:
- Method A computes the weight for each pixel based on its contrast, after which all the pixels from all the source images are averaged according to their weights.
- Method B finds the source image where the sharpest pixel is located and creates a “depth map” from this information. This method requires that the images be shot in consecutive order from front to back or vice versa.
- Method C uses a pyramid approach to image representation. It gives good results in complex cases (intersecting objects, edges, deep stacks) but increases contrast and glare
There are settings to adjust, but to start with, the defaults are fine.
The software takes just a few seconds to handle these 26MP jpegs.
I’m using the depth map method since I’ve a nice clean set of images from front to back.
The result is presented and I can choose what to do with it.
Here’s the stacked image [click to enlarge]
A better set of photos
On closer inspection, you can see that the far corner of the car is a bit soft. It seems that I wasn’t careful enough to make sure the stack was deep enough. Most likely I forgot that with the extension tube, the far focus point is closer than I’d thought.
The new stack has 21 images in it and is sharp from back to front.
This shot shows the depth map being constructed during the stacking. It clearly shows how much of a focus step is taken between each shot. Lighter colours are further from the camera.
The background just gives noise. In my normal work I often try and make sure the stepping extends further back to give cleaner edges to the final stacked image – this is the sort of stuff you tweak settings for. The defaults are just fine for this example.
Here’s the car, from the different angle.
There’s also this version after I’d cleaned the car a bit, showing some of the detail that I remember playing with ;-)
The depth map
The depth map that’s created, can be exported along with images for use with modelling and visualisation software.
Amongst the features in the more advanced version of the software is the ability to animate a combination of the depth map and stacked image
It’s a neat effect, even if I’ve never quite found a commercial use for it.
I’ve a bit more about this option in part #2, looking at moving the camera and stacking.
You don’t have to use focus stepping software (or the built-in function in some cameras). This example is from my review of the Laowa 25mm f/14 relay macro lens.
The lens is manual focus, with a close focus point only a few millimeters from the tip.
Just one shot showing the view from down amongst the spines.
The lens focus ring (at the camera end) has a good range of rotation (throw). By moving the focus ring by a millimetre or so and taking a photo, I created a stack of images.
The set stacked fairly well, although on a paying job I’d do rather more retouching where some overlaps of spines are not quite right.
Here’s the stacked result [click to enlarge]
At a larger scale
The focus stacking technique isn’t restricted to close-up work. Just as you can use a tilted lens to reduce the depth of field in a view – the model world or ’tilt-shift’ effect, you can use focus stacking of photos of a model to eliminate some of the focus depth cues that suggest it’s a model.
The lens, a Canon EF24-105 F4L was stepped front to back in single focus steps
The models are ‘O’ gauge and from Ellis Clark Trains in Skipton.
If trying to make a model look full size, then pay very careful attention to lighting and shadows, since clarity of focus is only one factor in the illusion.
If you’re photographing products then do consider how much you need to show the scale/size of the object, especially since with extreme detail comes dust and minor scratches/blemishes.
Of course, you can use basic focus stacking for any situation where depth of field is limited, but remember, it can be tricky when there’s any movement in the scene between shots.
Training – in normal times we offer bespoke UK on-site training for product photography for companies, which can include macro photography. See our training services for more info.
Software to try
- CombineZP – windows only, free [WP]
- Picolay – windows only, free [PL]
- Zerene Stacker – Mac/win specialist software with pro level options like Helicon [ZS]
- Helicon Focus – Mac/win software that I use for some of my work.[HeliconSoft]
- Affinity Photo – Image editing software that includes effective stacking capabilities [Serif]
- Photoshop – includes focus stacking, but not at the level of Helicon/Zerene
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