Building World Class Photography Turntables
In an earlier article we discussed how photography turntables can efficiently capture 360 images that can be used for eCommerce product photography applications. Turntables have multiple usages, including: 3D scanning, photogrammetry (structure from motion), panoramic imaging, scientific & research, engineering, quality control testing and others. This article highlights the engineering challenges of building a world class photography turntable and how these challenges were overcome by our engineering teams at Iconasys.
Let’s review the properties a photography turntable should have and for each property we will discuss how Iconasys Platinum Series Turntables implement them:
- Start and stop control. Ability to stop when the photograph is taken.
Controlling the turn and stop motion of the turntable is dependent on the type of electrical motor the mechanical design uses. Since all tables are electrical tables (no internal combustion engines) the options for the type of motors were: alternate current (AC), direct current (DC) or stepper. Controlling the position for an AC and DC motor design requires the use of encoders and more complex feedback loops. For convenience and simplicity, we opted to go with a stepper motor design.
Start/stop photography turntables provide benefits that include:
- Ability to use slower shutter speeds & smaller aperture during capture (to achieve ample depth of field)
- Ability to let strobes recharge during in between frames (our Shutter Stream 360 Product Photography Software even provides user the ability to pause prior to capture in the chance additional recycle time is needed for the strobes)
- Ability to capture more images per 360 rotation (think n the case you are using a turntable that spins at 0.3 RPM – that is ~20 seconds per spin – not likely enough time to capture say 36 images per 360 rotation).
- Ability to use with Focus Stacking (if required for Marco Photography)
- Speed control. While photography turntables don’t need to rotate very fast, it is important to have a certain range of speed control. For turntables carrying a lot of weight, whiplash can be a problem when the turntable starts or stops (causing turntables to over/under rotate in some cases). Thus, speeds of up to 2RPM are usually high enough.
A stepper motor is controlled by a digital stepping driver that provides a wide range of flexibility. One feature, in particular, is the ability to control the micro-steps. For a motor that has 200 steps per rotation, micro-stepping divides the full step into smaller steps that can go as high as 256 micro-steps per motor step. Thus, if using a 10x micro-step setting for the stepping driver, a 200 full steps motor will now have 2000 micro-steps per revolution. Micro-stepping allows us to control the maximum number of steps and speed, for a given maximum stepping frequency. The motor can be slowed down further by simply reducing the stepping frequency via the controlling computer.
Besides the micro-stepping control, our Iconasys Platinum Series Turntables have two different methods for torque multiplication. The Platinum MID and LRG product photography turntables use high quality belts to provide torque ratios of 1:9 and 1:20. The Platinum XL turntable provides a torque ratio of 1:56 via a worm-gear design. Torque ratios have two main advantages: (a) increased turntable torque and (b) vibration dampening.
An added benefit to variable speed control, is the ability to use the turntable for creating both 360 product photography and 360 product videos.
- Direction control. Ability to change direction.
Ability to control direction is a free benefit of using stepper motors.
- Angle resolution. This refers to how accurately one can select the position of the photography turntable, or equivalently, how many different stop positions can the table achieve in one complete turn. For photogrammetry applications this number might be higher, in the range of several thousands of stops per revolution.
As described earlier, in the “Speed control” section, angle resolution is a direct result of the torque ratio and the micro-stepping setting of the digital stepping driver. Iconasys Platinum Series Turntables start with resolutions of just over 10,000 steps per rotation and can go up to 40,000 or more. There is one catch to stepper resolution. The maximum pulsing rate of these stepper motors tops around 400Hz. This means that increasing the stepper resolution via micro-stepping will slow down the maximum turntable speed.
- Angle accuracy. This is closely related to resolution and it refers to the level of play in the angle position. Once the table is commanded to go to a certain position how accurate, in degrees, is the table going to be at the commanded position. Ideally, accuracy will be less than the angle resolution.
The Platinum Series MID and LRG photography turntables use a belt mechanism to control the turntable’s rotation. With a properly tensioned steel belt, the table has no noticeable play and thus the angle accuracy is less than the angle resolution. The XL model uses a worm-gear design. This provides excellent torque ratios (1:56) but does have a small play in the gearbox. For this design, the table has the option to employ two static breaks that keep the table fixed at its stopped position. As long as the table turns in one direction the accuracy should be less than or equal to the angle resolution.
- Vibrations. Ideally, the turntable will minimize vibrations. This is especially important if the turntable design uses a stepper motor, as they can introduce significant vibrations (which can easily be seen when shooting small objects like 360 jewelry photography).
Stepper motors are notorious for introducing vibrations. These vibrations can be controlled via high quality stepping drivers and torque ratios. The higher the turntable torque, the smaller the rotational vibrations. Our Platinum Turntables use high end stepping drivers and have torque ratios up to 1:56.
- Photography Turntable software development kit (SDK). This refers to how easy it is to integrate the turntable into a custom-developed application. Ideally, the turntable SDK is freely available and will allow any third party to develop custom interfaces for the turntable.
When developing our turntables, we worked hard on maintain a common software interface for all of our Iconasys turntables. This interface is freely available as a C++ SDK. Internally, our 360 Product Photography Software uses the same freely available SDK for controlling the tables.
- Ability to suspend objects for bottomless and topless views. This feature is especially important when photographing hanging jewelry, such as necklaces, or when doing 3D scanning and photogrammetry.
All Iconasys Platinum Turntables support the ability to hang products.
- Loading capacity and manufacturing quality. A decent turntable should be able to handle a wide range of weights and be built out of quality materials that can last a long time.
The Platinum MID turntable holds up to 75 pounds, the LRG holds up to 300 pounds and the XL supports up to 500 pounds.
- Beauty and elegance. A world class turntable should be beautiful and elegant. It should be a tool that any photographer would want to use and look at.
The MID and LRG Iconasys Platinum Series Product Photography Turntables are designed using a beautiful aluminum cylinder as the main module of support. Roller bearings and pulleys are both functional and extremely beautiful. The extra-large design continues with the same simplistic look. It minimizes the use of moving parts, embedding all the mechanics inside a beautifully custom-designed gearbox.
- Miscellaneous. This catch all category includes: the ability to extend the turntable with larger platforms, ability to raise products for shadow-less photography and a quick and efficient setup.
At Iconasys we have enhanced our Platinum Series Photography Turntables with the ability to extend the platforms and to add risers for shadow free photography.
In conclusion, we have discussed different features that make a photography turntable a world class turntable and we have described how our engineering teams at Iconasys have approached these design features in building our Platinum Series Photography Turntables.