Helicon Focus focus stacking part 2
Helicon Focus review – pt. 2
#2 Moving the camera for depth of field
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Part 2 of Keith’s Helicon Focus review looks at moving the camera to acquire images for stacking.
Keith uses Helicon Focus to stack multiple images for some of our specialist photography work. The stacking allows for increased depth of field and is particularly useful for close-up and macro photography.
All of Keith’s Macro related articles and reviews are listed in their own category in the dropdown menu to the right.
Stack from a moving camera
In part 1 of the review, I looked at using focus stepping to acquire a set of images that could be stacked to give greater depth of field.
This works with lenses with autofocus and you can manually step focus for manual focus lenses. However, what about just moving the camera?
I’m using the same set-up as before, with the Canon EOS RP mounted on a slide rail.
The rail is mounted on a pan/tilt head attached to a hefty studio stand.
My stand came from eBay a few years ago. New ones are expensive, but keep an eye out for used ones appearing – mine cost £150 [eBay] Note though that they are heavy.
The camera is physically moved from this start point.
To a second finish point.
Note the change in image scale.
At first sight this looks the same as when you change focus, but is subtly different in that the viewpoint of the camera is changing.
From a practical standpoint, this means that the moving camera approach works better for relatively small scale working. That’s good, since my principal macro lens (the MP-E65) has no ability to focus at all. The ‘focus’ adjustment sets the magnification [See my original MP-E65 review for more]. I’ll come back to this in the final part of stacking articles.
I’m just using a simple screw thread driven rail. These are the black knobs at each end.
The stacked photos
There’s no need for precision in the movement, just remember to take a photo for each movement of the knob. I made sure to use a cable release to avoid any shake. I had EOS Utility running at the same time, for checking focus/lighting/exposure. Firing the cable release captured the photo, which was downloaded straight to my computer.
Since I was just taking JPEG images, it doesn’t matter that I ended up with 37 photos to stack. The processing still took only a few seconds.
Here’s the depth map from the stack (Method B) showing the size of steps.
In making the video clip in the first part of the article, I just used the defaults to create a short video clip. I’m using the 3D Viewer option in Helicon Focus
Helicon focus gives you quite a bit of control over setting, but remember you are limited to surfaces that were visible in the photo stack, so this isn’t a solution for making images of products you can just move and rotate.
There is also the ability to take snap shots and create basic 3D model files
A snapshot exported from the 3D viewer.
3D Images for your screen
There is also the option to produce 3D screen images.
This first one needs looking at with crossed eyes. With my eyesight I find the straight parallel style of stereo pairs difficult to use on screen – but it’s an option if you wanted to print images for a stereo print viewer.
Click to enlarge and see if you can get the stereo feeling of depth.
If you’ve a red/gree pair of coloured glasses, here’s a R/B anaglyph image.
Automating camera movement – Helicon Remote
It would obviously be nice to have the camera movement automated in some way, such as I did using EOS Utility in part 1. HeliconSoft produce another application called Helicon Remote that addresses this.
The software works well at basic step focus stacking.
Here I’m using an EF24-70mm F2.8L lens, setting near and far focus points. I find Helicon Remote easier to use for basic work – simple to set up and use if your lens will handle the close focus.
Here’s a crop from the stacked image of 28 JPEG files. I’ve used my EOS 5Ds 50MP DSLR for this, along with the flash setup shown later.
Heliconsoft give the following uses for Helicon Remote:
- Tethered capture of images and video – shoot remotely to automate the whole process, control all the camera settings remotely even in the most awkward camera position and view angle, minimize camera shaking and make perfectly sharp and precise shots.
- Focus bracketing – set up your camera, tether it to your computer or telephone, adjust the camera settings and let it make a series of shots with focus shifting from shot to shot to be stacked into a fully-focused image.
- Exposure bracketing – take a series of shots with different exposure for further merging into a high dynamic range (HDR) image.
- Time lapse – adjust the settings and let your camera make series of shots with the set time interval and see how your object is being changing over time.
- Burst shooting – control high-speed shooting from your computer or telephone – set the number of shots or just press the Start and Stop buttons.
- Burst focus bracketing – set the camera on macro rails and combine burst shooting mode with focus bracketing to get a series of incrementally focused images made with minimum time interval.
There are details of just what cameras are fully supported at HeliconSoft (my EOS RP isn’t yet amongst them)
Motorised movement – the Stackshot
For the real precision I need for macro work, not to mention my occasional stacking of a hundred or more shots, I use a motorised Stackshot rail. [Cognisys]
The Stackshot can move the camera by just a few microns,. I’d note though that if you are doing really small scale stuff you’ll quickly find how solid your floors are. I’ve seen camera shake from Karen walking round her office upstairs. This is one reason to move to flash lighting, where the short duration of the flash will reduce any blur. Shooting with liveview will also reduce any mirror related vibration.
I got the extra length version of the rail. You can see the stepper motor at the top left and the lead screw that moves the mount plate.
The device is driven by a control unit. The display here is for manual operation of the stackshot. Normally I plug a USB lead into it to control it from Helicon Remote. The device is capable of a lot more than the simple motion control shown here, including firing the shutter of your camera.
For convenience I’ve put the Manfrotto slide on top of the stackshot. If you’re going for a setup like this make sure its a good quality rail with no slip or looseness.
Helicon remote works with several movement controllers.
The options vary with the device. The delay between shots allows everything to stabilise between movements. If you’re using flash, then you might want to increase the step time since your flash may have difficulties in reaching full power, or overheating if you fire it too rapidly.
Here’s the final setup.
The flash is out of the way firmly attached to a tripod arm. You want to move the camera, not your lighting setup.
The two small softboxes are from my Laowa KX800 Twin Flash. I reviewed this some time ago, and Karen has always liked it for jewellery photography.
The CFL lighting is enough to illuminate the subject for focus checking. The cardboard behind the subject is aluminised, reflecting a diffuse backlight.
I’m checking composition with a live-view display. The exposure is quite long at 0.4s. When firing the flash, I’ll up this to 1/125, so that only the flash contributes to subject lighting.
The near focus point is set above, and the far point below.
The near/far points are set (A/B) and show the number of steps the Stackshot will make.
Not wanting 6250 photos, I’ve set the interval count to give 16 shots, a good range of photos for this subject.
The number of photos will depend on how thick the depth of field is for each shot. There is an ‘Auto’ function, but I prefer to set this manually.
You can take test shots to set flash levels and direction. Watch out for specular reflections though, since these can confuse the stacking process sometimes.
The stack of 16 photos shows the change of scale I mentioned earlier.
Helicon Focus allows for this. If you were using a telecentric lens, the scale change would would not be there, but telecentric lenses have quite a different look to their images.
Telecentric lenses? – See my article about how to make a telecentric macro lens out of old lenses you may have sitting around unused.
I mentioned the three stacking methods in part 1 – For some subjects one is obviously better, but for this little car? Take your pick… [click to enlarge]
Photo of a broken disk drive
For a bit more of a challenge I’ll show the interior of a broken hard disk drive from one of my servers. These do fail, which is one of the reasons I recently wrote about backup strategies for photographers.
If you have an old drive, don’t forget that sometimes there’s an extra hidden screw under the label.
Also, with big stacks of photos and lots of liveview use, a mains battery adapter for my 5Ds is a lot easier to use than having to change/charge batteries.
You can see the flash heads and softboxes connecting to the flash controller. This allows for different flash power settings to each head. It’s connected via a basic Canon flash extension cord, although the flash isn’t a ‘smart’ flash, so could be connected via a good old fashioned coaxial flash cable.
A test exposure shows I’m going to need to reduce the flash power a bit to reduce the intensity of some of those bright reflections. I’m working at f/8 here, but with the increase in effective aperture from the extension tube, I don’t want to go much higher.
Depending on the lens and distance I might even shoot slightly wider. Whilst many assume you need to stop down to improve image quality, I’ve noticed when testing true macro lenses that wide open or perhaps a stop less will give sharper results, albeit at the cost of more photos per stack to counter the razor thin DOF.
Here’s the result from stacking the 50 JPEG images.
50 (50MP) JPEG files didn’t take more than 20-30 seconds to stack.
Here’s the depth map, which you can see being built up as the files are processed.
Flat featureless areas sometimes produce artefacts, especially near highlights
Fortunately there are some useful repair tools.
In the example below, I’ve used one of the images in the stack as a source for cloning out some of the artefacts in the image above.
A particularly bad example is caused by these bright reflections.
Reducing exposure will reduce those highlights, but at the cost of making other parts of the image too dark.
Even so, the JPEG stack is easily cleaned up.
However, Helicon Focus can stack camera RAW files, converting them with the Adobe DNG converter, and then outputting a new combined DNG file. The 50 50MP RAW files took a lot longer to stack though. Some 15 minutes on my oldish Mac Pro
The DNG file just opens normally in Camera RAW.
Any way, here’s a slightly tidied up version of the file – somewhat reduced in size from the 50MP original, but still large enough [Click to view] to see a lot of fine detail. See a print of this in my PermaJet metallic gloss review.
A full size crop showing the top read/write head assembly.
Image quality issues
When doing photos like the one above for clients I’ll tend to take rather more time in setting up lighting and reflectors/modifiers. I rarely photograph the plants/insects/fungi that make up the vast majority of macro and close-up photography you’ll see on forums. It’s just that most of our clients are in electronics and engineering, where handling specular highlights is a common issue.
It’s for this reason that I’ll sometimes switch to making a stack of RAW files. However, whilst the built-in RAW stacking is impressive, it doesn’t allow me to fine tune the RAW files before stacking. What I’ll do is create a stack of RAW files and then using ACR export them as 16 bit TIFF files. This allows me to bulk process the RAW files applying adjustments, lens corrections and addressing colour corrections with things like custom DNG lighting profiles.
Here’s the tiny Colorchecker card I use for profiling, along with the effect of using it. [Profiles with a colorchecker Nano]
In the final part of this article I’ll dive into really tiny stuff and look at just what detail you can expect to see.
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.
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