For those not familiar with the Bratcam in its earlier, manually-driven form, here is the link to the detailed description posted about a year ago: Manual Bratcam.
Below is an image of the overall setup. I shoot tethered, which lets me see each capture on a large screen. For this illustration, I pulled up an image of a not-too interesting leaf mold, the subject of which I still had available to stick in front of the lens. The image was actually shot with a 60x objective, not the 10x objective shown below (oops). The subject lighting has been omitted for simplicity.
Here is a shot of the prior, manual, incarnation of the Bratcam. The orange line indicates the range of coarse adjustment available for placement of the camera stage, via travel along an Arca-Swiss compatible plate from Chris Hejnar. This is important because I use the rig with a variety of lenses with quite different working distances, with subjects ranging from the size of my hand down to the microscopic. (Often, I want to start with a “portrait” shot of something like a moss, then move in and take detail shots of specific features.) Since the entire camera stage—and not just the portion adjusted by the microscope dial—moves during initial positioning, I needed to mount a stepper motor so as to move with it. (In the current photos, you may notice that the old Hejnar plate has been replaced with a longer and slightly thicker one, also made by Chris Hejnar; I wanted longer travel without having to loosen screws to move the plate.)
I was going to build something to do this myself, but Lothman posted an image of a surplus unit he’d purchased on eBay. It seemed like precisely what I was planning to build, so I wrote the vendor to see if he had another. He did, and put it on eBay for me; I purchased it immediately. It is based on a focusing block that I think came off a Nikon Macrophot-2 or similar Nikon microscope, and was perhaps an aftermarket modification.
Here is the stepped microscope stage as it arrived from the vendor.
The image below shows the unit after some modifications (including replacement of the stepping motor) which I’ll discuss later. Note here that it has the stepping motor nicely mounted at a fixed (though slightly adjustable) distance from the microscope focus assembly. Also, the connection between motor and focusing assembly is made via timing belt. Benefits of a timing belt rather than a direct couple include reduced need for critical alignment of motor and focusing assembly, avoidance of transmitted vibration, and the ability to change gearing by replacing the timing pulleys and belt (not that I’ve found this necessary).
Below is a detail important for anyone wishing to build something similar—note the small screw for adjusting belt tension.
Don Wilson, my fabricator, helped me modify the unit for my needs. It is shown below, post modifications. (I’ve turned the unit around from the prior pictures, because individual elements are easier to see from this angle—so if anyone notices that the unit is facing backwards, it is.)
A: Four-inch quick release clamp from Kirk Enterprises
B: Top mounting plate made by Don Wilson
C: The fine and coarse focus knobs of the microscope stage on which the unit is based. Both are useable, though the fine one also turns the motor. That hasn’t actually hurt anything, but I avoid it. (I’m aware that this can send some current into the controller, though Cognisys has tested for this and not found it to damage anything.) The coarse knob does not turn the motor, so I use that one freely. Fine focus is easily done by pushing buttons on the StackShot controller. However, with an automated approach, I do a lot less fine focusing, since I like to prefer to shoot a few extra frames before and after the useful portion of the stack just in case; so now I just rough it in and hit “go.”
D: A portion of the purchased surplus unit—probably didn’t need to label this.
E: Bottom mounting plate made by Don Wilson
F: Another Four-inch quick release clamp from Kirk Enterprises. This one is mounted upside down to clamp onto rail "G," described below.
G: A 17.5-inch long, 3/8" thick Arca-Swiss style dovetail plate made by Chris Hejnar. He custom-made this one for me, but once he has the CAD file for something, it generally enters his “available on request” inventory. I use the Arca-Swiss standard in certain portions of the rig because it allows me to quickly pull the camera stage off the Bratcam for use on a tripod, and to interchangeably mount a camera, lens, or bellows on the rig. I wanted the rig to be modular.
Now, about the StackShot controller—what a gem! If you are considering automating your own rig, I highly recommend using one of these. Paul DeZeeuw, at Cognisys (the company that makes and sells the StackShot), is exemplary. He deserves a much stronger word of praise, if I could think of one—vendors simply don’t get any better than this. He helped me find a stepper motor of the size I needed for my rig; then he ordered it, terminated it appropriately for connection to the StackShot controller, and tested it.
My original unit came with a five-phase stepper motor, which is hard to drive. We replaced it with a two-phase motor compatible with the StackShot. This motor has .9 degree full steps, which gives me 400 full steps per revolution (most stepper motors give 200 full steps per revolution). The StackShot controller permits microstep resolution of 1/16th full step. My rig moves .015625 microns per microstep. One might have expected the StackShot controller to be cumbersome to calibrate, since the distance the camera moves per motor revolution is unique to my rig, and for that matter, so is the motor. But setting this was trivially easy, requiring just a couple of minutes.
The StackShot controller is very well thought out, and I’m finding it a pleasure to use. I have the step increment pre-entered for each of my lenses (very easy to do), so that taking a stack involves just a few quick steps:
1. Scroll down the menu to the “program” I saved for the lens I’m using.
2. Position the camera at the starting point for the stack (in my workflow, this is the point closest to the subject—I always work from near to far) and press a button to let the controller know that this is the start point.
3. Move the camera to the end point for the stack, and push a button to tell the controller that this is the end.
4. Hit the start button and walk away.
A couple of the nice touches are worth mentioning. If the stack has started, and I think of something I’d like to change, a single button aborts the process. Even better, another button push lets me redo an aborted or completed stack from the beginning. So if I want to change the lighting, I can do so and re-run the stack very easily.
Forward and backward buttons on the StackShot move the camera very smoothly and efficiently. In my rig, I can also use the coarse focus knob freely so I use it for rough positioning. I use the StackShot for fine positioning as well as stacking. The speed and ramp-up time are adjustable.
I already had an older and rather robust controller called a “SmartStep,” but when I started to program it, I realized that I’d much rather be taking pictures than learning motion control programming. Given how well thought-out the StackShot controller is, it is a zero-regret purchase. There will soon be options to operate the StackShot controller via computer (using software from StackShot or using Zerene Stacker). When that happens, I’ll likely be even happier.
Sometimes I use a camera and macro lens on the rig, without a bellows. Here is an image of the Bratcam in one such configuration. The camera is mounted on an adapter block made for me, not surprisingly, by Don Wilson. The main purpose of the block was to compensate for the removal of the bellows, and get extra height for tall subjects, but I figured that I might as well get some additional working distance while I was at it. The block consists of two Hejnar plates mounted on solid aluminum. The plates are adjustable with screws, so that if I ever need a few more inches of working distance, I can get them. Despite the fact that I have, for this demonstration, cantilevered the camera pretty far out, it is quite stable.
There are still some things on the “to do” list.
1. Dress the motor cord to prevent strain.
2. Perhaps add safety stops (so far, not necessary, but probably prudent).
3. Ask Don Wilson to raise the 17.5-inch Hejnar plate a bit—taller specimens require that I fully lower the subject stage, and sooner or later, I’ll have a subject that’s just a bit too tall. Alternatively, I could use a couple more adapter blocks in various thicknesses.
4. Ask Don to convert the vertical pipe that holds the subject stage from a one-piece unit into a two-piece unit. Sometimes I want all the vertical travel I have; other times I’d like to have a shorter pipe to make it easier to place a background and permit me to swing the subject stage 180 degrees for more working distance (I could do it now, but the pipe would block the camera’s view). Don is confident that he can cut this pipe and add a threaded rod that will let me rejoin the two pieces as needed, without sacrificing stability. I’ve been waiting until other height issues were worked out (this motorized stage, for example, is not as tall as my old manual one) before deciding where to make the cut.
To anyone who has made it this far, sorry for such a long post. When I’m studying other people’s rigs, I appreciate details—so maybe someone else would, too.
--Chris Slaybaugh
) It's something I was waiting to do until I knew the final height of the stepped stage.
