A software development that permits unprecedented tethered control of focusing and exposure changes
The name Helicon will be familiar to many photographers for their Helicon Focus image stacking software – out of the same stable comes a revolutionary program – Helicon Remote that allows tethered shooting with fine control of focusing for stacks and of precise exposure for HDR..with both together if you so wish.
Automating stack creation so that steps are precise and uniform
The extremely bright young Ukranian mathematicians behind Helicon Focus have gone further with Helicon Remote and produced something that could revolutionize image stacking for many of us. The software has been available in Windows for some months and is currently in a Mac Beta version and is available as a download to those already with a Licence to use Helicon Focus
stacking is not easy with living subjects outdoors - crab spiders can be accommodating and remain still
Helicon Remote enables you to control the lens motor in the AF system of a lens from your computer. The software allows you to specify both the number of shots in the stack and the distance over which you wish to shift the focus.
It currently works with Nikon and Canon cameras that have Remote / Live View: a feed is taken by a USB lead to a computer where there is an on-screen display of the image and a series of controls that allow you to shift focus in a lens and create an image stack. The screen-filling cability and quality of the display is much better than that afforded by the Nikon Control Pro 2.
Furthermore, Helicon Remote is also configured to drive a StackShot focusing slide (from (Cognisys inc) that I hope to be be able to reveiew here, soon. The device is not rack & pinion driven but utilizes precise lead screws (micrometer screws) coupled to a stepper motor that can be programmed to advance by a fixed amount (as small as 0.01mm) after each shot.
Helicon Remote operates by changing focus in your lens by feeding an electrical pulse to the focus motor. It is purely electro-mechanical and the autofocus mechanism of the lens is over-ridden. Thus it does not matter what the AF part of the camera sensor "sees" because you set the range of focus (using Live View) on the computer screen using on-screen controls.
a stack of 34 images taken at 1000th sec f/5.6 resuklted in this shot of a periwinkle. The shallow background was obtained with a 150mm f/2.8 macro
How it operates
- It is simple, you set up with your camera on a tripod, frame the subject .
- Now you adjust on-screen arrows (very fine, fine and coarse) to get precise closest focus at the nearest point, click to select: repeat at the far point, select that.
- You can reverse that procedure for the software will shift focus either towards the camera or towards infinity.
- With two endpoints fixed you now have to establish how many shots to take and the distance between them.
- Yes, you could do this by ‘guesswork’ which would involve maybe looking up a d.o.f table, rotating the focus ring a tiny bit, take a shot and repeat.
- Howevere, the Helicon designers have, with their usual ingenuity, included a calculator. With your macro lens coupled to the camera the software recognizes the lens and the aperture you selected: when you have selected the start and finish points it can be used to tell you how many shots to take/it will take. Underlying this is a non-linear relationship between rotation of the lens focus ring and change of focus ie. regular changes in focus ring rotation do not create uniform shifts in focus.
- The number of steps depends on the aperture used and you are told to use steps smaller than the depth off field (you set these) so each image in your stack overlaps slightly and when combined will produce a smooth transition.
- How fine those steps between images can be depends on the motor in the lens
- You click on the screen (top menu bar) to start the sequence- images can be stored in any specified folder (the CF card in the camera is removed) and the results then opened in Helicon Focus for rapid stack creation.
A stack of 18 images was used for this image of a Nigella (love-in-a-mist) seedhead
Using Flash
If you are using flash then, in the preferences, you can specify the time lag between shots so that the flash units can recharge - ensure the same level of illumination from one image to the next. If this is not maintained than the stacking program produces a result but it is not the best you can get.
Daylight Stacking
If light levels are high enough you could use 1/400 of a second shutter speed at f/4, for example and take a rapid sequence since there is no need to wait for flashes to charge. This would depend on how fast your camera can shoot a sequence (set to high-speed) -- at such a shutter speed camera vibration, though present, is more or less eliminated in each frame, though it could be noisy and some insects such as large butterflies are sensitive to that. Lock up the mirror. For studio use or even outdoors on a table close to a house you can use the camera with a mains adapter. Live view quickly depletes a camera battery.
USING FOR TRUE MACRO and Photomicroscopy
The focus control works very well with a converter added but not with supplementaries for that a focus slide is better. Stacking is a way of getting the best out of a macro lens at its optimum apertures - such depth of field is not possible otherwise
Using movements within the lens focus mechanism is not always the best way to get precise focus – especially when using supplementary or stacked lenses. You’ll find that there is noticeable ‘image breathing; as the macro lens is focused internally ie magnification changes with shift in focus.
In such cases it works far better with the camera on a focus rail.
If you couple your camera to a microscope or use lenses on a bellows where there is no AF you can use the manual option within the program to create an image stack.
Sometimes, with bellows and other devices the effective aperture is so small it is difficult to focus directly on the viewfinder image. If you use the camera's 'live view function' there is a built-in image intensifier (light amplifier) that gives you a good image on the camear LCD. This is is even better on a high-quality computer screen using this program for it produces a large, screen-filling, live view.
Helicon Remote control has revolutionized. outdoor stacking, the use of my optical bench and a Zeiss Tessovar Zoom macro that I have never found easy to focus since its widest aperture is about f/45 – with the live view and screen display this program offers that has changed – I will explain in Part 2.
Also this software allows fine control of exposure sequences for HDR.