I recently bought a number of items from Edelkrone, that I consider one of the best if not the best supplier of cinematography peripheral products for pro's and sophisticated enthusiasts like myself. For this article in particular, I am referring to Edelkrone's SliderPlus Small slider, their Action Module and their FlexTilt head. In the picture above, the slider is easily seen; the action module fixed on one slider end (here shown on the left) and the camera is mount on top of Edelkrone's FlexTilt head, which in turn is mount on top of Syrp's Genie. The entire rig is mount on a video Manfrotto tripod.
What Edelkrone's slider does is broadly known to any serious video enthusiast. It's based on a clever mechanical concept that enables the camera a total travel distance larger than the length of the slider itself. Visit their homepage to see how. Their Action module is a compact mechanism that easily mounts on one end of the slider and automates the transport of the slider belt and subsequently the camera bridge to achieve smooth video slides, or timelapses with slides. Finally the Flextilt head is an interesting tripod mount for cameras that allows a lot of flexibility. I am ecstatic about all three of these products.
Edelkrone also has another product that resembles the Action Module and attaches on the opposite end of the slider. It is called the Target module. What this achieves is, when you enter the distance in the module between the camera and the object that the camera is focused upon, then, when the camera slides along the rails (courtesy of the Action Module), it is also made to rotate as well (Courtesy of the Target module) in order to maintain the focused object in the centre of the Viewfinder (VF). In other words, the camera follows the object while it moves on the slider. Shots achieved this way give the impression that the camera moves smoothly around the object in question. Excellent and very cinematic camera movement for product ads but also in plain vanilla cinematography. As an example, almost all close-ups and medium shots, especially those with dialogs, in the White Collar TV series are shot like this. Rarely the camera remains static during shoots. They also use loads of timelapses to add a powerful dynamic to the entire show.
I was considering purchasing Edelkrone's Target module as well, when I fell upon Syrp's Genie. This is again a very interesting concept. It's a sturdy box with two types of base to be mount upon. One aims at supporting any given manual sliders and the other is used for panning. Depending on which base you mount the Genie on, it will either rotate (for pans) or transport itself along the rails of a slider (for slides). Indeed it seemed quite an interesting piece of equipment and I therefore decided to procure that instead of Edelkrone's solution. I had a gut feel that with Genie I could still achieve what Edelkrone's Target module offered and a lot more. And indeed it does.
This article is about using the Action module and Genie combined to achieve the same result as when Edelkrone's Action and Target modules are used in unison. Edelkrone made sure that the only parameter needed to sync the two modules (and maintain the focused object in the middle of the VF) was the distance between the camera and the target object. The rest they have calculated and embedded in their firmware algorithms. In other words, if you go Edelkrone all the way it's very little you need to prepare to achieve great results all the time.
However, you can achieve the same results with a little extra manual tweaking and this is what I describe hereafter.
fig 1 : top view of the set up
The figure above shows my setup, whereby the object, which the camera VF is focused upon, is found at a distance L from the middle position of the camera slider travel. At position A the camera is turned at an angle a/2 with respect to the vertical direction in order to place the focused object in the middle of the VF. As the camera mechanism progressively moves from A to B, Genie (with the camera on top) rotates counterclockwise (CCW) for a total angular travel of angle a, in order to continuously maintain the focused object in the centre of the VF. Also, the total travel time of the camera system from A to B should be the same with the total angular travel (rotation) from the camera's initial angular position, moving CCW to its end position. Of course, if one plans a move from B to A, then Genie needs to rotate itself in the clockwise (CW) direction by the same angle 'a' always.
So the process to achieve this in the setup above is as follows:
1. I first made the decision to use 10 secs as the total sliding travel time (and Genie rotation). Genie accepts this duration as a parameter, but in Edelkrone I had to apply trial and error to define the right speed for the travel distance. For 345 mm distance from A to B, I had to select 32 as the camera velocity and 10 as the maximum acceleration (meaning, no easing-in and -out at the start and end of the linear travel). Indeed, with these parameters the camera on the SliderPlus travels the 345 mm distance in acceptably ten seconds.
2. The camera, mount on the FlexTilt Head remains fixed in terms of angular displacement with respect to the Genie body. It is Genie that automatically rotates about its vertical axis. Other (height or tilt) adjustments are done via the FlexTilt Head. While adjusting the setup and focus on the target, it is perhaps easier to check results on the camera monitor at the back of the body instead of thru the VF.
3. Next, one needs to set the rotating angle parameter in the Genie settings. Measuring the distance L and applying the simple formula shown in the figure provides a first good approximation of the rotation angle that needs to be set as a Genie parameter. Also, don't forget to set (Genie's Advanced Settings) the Easing-in and -out to OFF. To make sure the angle works, you trigger Genie to rotate to its end position and in parallel you may move manually or automatically the slider to position B. You then check the camera to verify that the object has still remained in its initial VF relative position. If not, depending where it ends up to, you may have to increase the angular Genie parameter or decrease it. If the object is left of the original focus position it means that the angular parameter is set low and needs to increase a little. If the object ends to the right, the angle was too large and needs to decrease. Act accordingly and check again until you achieve perfect alignment.
4. After the angle is entered in the parameter, and the Action Module was programmed in the Wizard mode to travel from A to B in ten seconds, the system may be set in motion. First you prepare the video shot parameters on the camera and hit the Record button next. Right after that, press the Start/OK buttons simultaneously on both, the SliderPlus and the Genie. Both devices start automatic motion, with the SliderPlus sliding from A to B and the Genie rotating the camera in CCW direction. In ten secs the travel is over, and one may set the Recording function back to standby.
This is certainly much more of a burden compared to Edelkrone's Target module. On the other hand, if you happen to own other sliders, as I do, you are actually adding value to those, even more so if motorised sliding was not previously an option. Unfortunately, Edelkrone's Action Module only fits (for obvious reasons) Edelkrone sliders.
On the other hand, once you calculated the angles for a few practical values of L, you can memorise what goes with what, and don't have to go thru the calculation and trial and error burden each time. For instance, I know that for a distance of 85cm the angle is about 20 degrees. If I made sure my target object is at 85 cm, I could always use the Genie preset that I have already stored for these particular parameters, and Bob's your uncle. If I don't like the VF scenes at the distances I preset, I can always use different lenses or zooms to adjust.
A common problem on similar devices, like Genie and Slider+, is the associated noise their motors produce. But as most people shoot B-rolls based on similar setups and use external audio equipment for better sound control, the noise will get suppressed in post and in so doing, it is less of a problem.