Last week, we looked at what’s in my bag when I was using the Alpa Focus Stacking System on loan. Today, I discuss how the system is used.
Using the Alpa Focus Stacking System for watch photography
The Alpa Focus Stacking System is first assembled as shown below by connecting the various components to each other. The flash trigger fires off two Profoto strobes which provide the flash lighting to the cube which serves as a portable soft box where the watch is placed.
Set up in this configuration, I put the back in Live View mode to see the subject on the rear screen. The Phase One IQ3 100 features a CMOS sensor, and has the ability to zoom in to 100% for critical focus. I can also tether the back to my MacBook, but I did not do so. The Novoflex control unit is set to Bellows Mode, and the parameters chosen for the focus stacking.
I start by moving the rear standard of the bellows unit where the FPS and digital back is mounted to the near position where I want to be in sharp focus. I can use the zoom function to see this at 100%. This position is then saved into memory on the Castel-Micro control unit.
The bellows is then moved to the far position where I want sharp focus, and saved. I then chose the number of steps needed from the position of near focus to the position of far focus. For the A. Lange & Söhne Datograph pictured, I chose 13 frames. The system does not offer a calculation based on the aperture chosen, the near and far points and an assumption of the circle of confusion to suggest the number of frames needed to cover the image. So this selection is manual, and based on user experience. That too is saved.
The control unit further allows a time delay between frames so that it can allow for the strobes to recharge as necessary. For my Profoto system, this is not essential, especially af f/5.6 where the strobe is set at 1/8 power, it is ready to discharge immediately after each flash. Then the Novoflex controller is set to begin the stack execution, and it automatically executes the number of frames chosen by moving the lens in equal steps from near to far focus. It is also possible to reverse the stack from far to near as desired.
After the frames are made, the raw images are processed in Capture One, and exported as full sized jpegs. These are then fed into the Helicon Focus software which generates the focused-stacked image. The stacked-image is ready for further processing in Photoshop to create the desired image.
The system is not without its problems. I have mentioned the steep learning curve. The back has to be setup for zero latency and to use an external shutter. The back is placed in LV mode for setup, and before start of the stack sequence, it has to be placed into the file review mode. If I fire the sequence in the LV mode of the back, the system fires once, and stops. Regardless of the number of frames it has been commandeered to perform.
The system also have other quirks. For example, the digital back does not capture the aperture information of the lens, as the Rodenstock does not have contacts to inform the back of the aperture setting. However, on Phase One backs, there is the ability to manually set aperture on the EXIF via the back. If you use a Hasselblad back, this critical information will have to be recorded manually, and not in the exif data. The Alpa FPS system does not reliably inform the back of the shutter speed. In my use, the FPS is set to 1/125s but the IQ3 thinks the shutter speed is 1/40s and records it as such. This is merely an inconvenience, as when used with flash, the FPS is always set to 1/125s.
At startup, the Novoflex Castel-Micro is quite slow, as it needs to move the rear standard bearing the FPS and digital back to an arbitrary start position before it becomes ready for use. Subsequently, moving the bellows to the first point for near focus and then to the far focus point is equally slow. This is despite Novoflex providing three speed settings, of which none are particularly quick, and there is no quick set mechanism which releases the lock for rough positioning. Perhaps a victim of the desire to be precise, as the system can place the back to within a smallest repeatable step distance is 0.2µm. And finally, the system is cumbersome and heavy. Not a big problem for a permanent setup in a studio, but as a traveling system, it is challenging.
As I have previously outlined, the focus stacking is one solution to the problem of getting sufficient depth of field in macro photography. This problem of obtaining sufficient depth of field can be solved several ways:
- use a smaller sensor like the micro four thirds. The smaller sensor will need a lens of shorter focal length for a given magnification, and will exhibit greater depth of field for any given aperture. In my Panasonic GH-2 setup, the macro lens for 1:1 magnification is only 45mm, and as the frame is smaller as well, depth of field across the dial can be achieved.
- use a tilt and shift system like the Sinar P or the Hasselblad HTS 1.5. Tilting the lens will move the plane of sharp focus to coincide with the subject, in this case the inclined dial.
- focus stacking. This can be achieved in several ways. Many newer cameras have focus bracketing in their drive mode which is very similar to what I have shown in the Alpa example here. Set near focus. Set far focus. Set number of steps. And fire the camera. Assemble the frames shot in Helicon Focus, and get the resulting image.
- These can be easy to use and automated like in the Phase One XF where after setting the near and far points the camera figures out how many shots and steps needed to cover the entire range after taking into consideration the aperture and using an assumed circle of confusion. The near and far points can also be quick set via the autofocus or manual focus for a rough focus, and zeroed in in step mode for critical focus.
- Or a bit more manual like in the Fujifilm GFX or Sony A7RV (review soon) system. Here, the photographer has to use his own judgement and experience to choose an appropriate number of steps, and step size.
- Or by mounting the camera on a macro rail and moving the entire camera assembly. I used this method for the photographs in my book – A. Lange & Söhne: The Pour le Mérite Collection (still available, and now on sale! Email me!) with the Hasselblad H3D-39 and a manual Manfrotto focusing rack.
- Novoflex also have a manual focus rack or and a manual bellows system.
The Alpa Focus Stacking system is more elegant approach with bellows focusing. This eliminates focus some of the issues faced by the other focus stacking systems like focus breathing which is a lens property and variations in image size one moves the camera mounted on a macro rail. And is ensures repeatability, which is difficult to achieve with a manual bellows system.
The Alpa solution includes the Novoflex automation at a very high precision, which is also repeatable. In addition, it becomes particularly attractive as it is modular and allows the use of the fabulous Rodenstock Switar 105mm f/5.6 FL lens as well as a flexible choice of backs, including the Phase One and Hasselblad backs. However, the downside is that he Alpa Focal Plane System has a very steep learning curve, is heavy and is cumbersome set up. It is also a rather expensive option, costing some CHF 24k before adding the digital back. A new Phase One IQ4 100 Trichromatic back has a retail of CHF 30k, or the Hasselblad CFV II 50C back will set one back an additional CHF 8k.