Want to be able to adjust your camera without loosing tripod alignment to shoot perfectly aligned multiple images?.......................

This Instructable shows how to build a simple device to allow you to return your camera to virtually exactly the same spot and orientation. Moreover the support can be built for about $20 to $30 dollars depending on options and what you can salvage. I have called the device "The OB-Pod" from Optical Bench and tripod. One of my lab friends pointed out that it was effectively a portable optical bench (thanks Anton).

So why would you need to do this?.................
Nearly all the latest forms of photography to be come popular are multi-image techniques and/or involve changing filters:
(1) HDR (High Dynamic Range)
A number of photographs are taken with different exposure settings and they are combined to produce an image with control of local contrast.
(2) Focus Stacking
A number of photographs are taken with different focus settings and they are combined to produce an image with a greater depth of field.
(3) Other Image Stacking Techniques
Image stacking has been used to reduce noise, reveal moving structures, artistic effects etc.

These first 3 are referred to as image stacking techniques. The common problem is keeping successive images aligned; this is usually remedied by careful use of a tripod and software. Image alignment software is good but you get the best results if the images are aligned as perfectly as possible in the first place. Many digital cameras have built in exposure bracketing but it is limited; to get better results you need an expensive remote controlled camera. Most of us though, try changing the camera settings by fiddling with the camera while it is on the tripod, but pressing menu buttons etc is enough to put the camera out of exact alignment. The loss of alignment problem is even worse if you want to stack images shot with different filters, changing a filter without the camera moving is really hard on a tripod. It would solve these problems if you could just take the camera off the tripod, change the settings and put it back in exactly the same place.

(4) Time Lapse
A large number of photographs are taken with equal temporal spacing. The photographs are linked together as a movie to provide an accelerated view of the action.  
(5) Stop Action
Inanimate objects or images are photographed with mechanically applied motion between shots. The photographs are linked together as a movie to provide an animation.

Time Lapse and Stop Action normally require leaving a camera in one spot for a long time; this could tie up your favorite camera for a long time. Some time lapse sequences go for more than one day eg Panama Canal Miraflores locks covers a whole week from the same location. Rather than tie your camera up for a week or more it would be very useful if you can take your camera away and return it to exactly the same place later on particularly if your camera is out in the weather.

(6) IR Photography with an older SLR
It is quite popular to modify an old camera to be an IR sensitive camera by removing the internal IR blocking filter and using an external filter to block visible light. If you modify an early DSLR (pre-live-view) to be an IR camera you will not be able to see through the viewfinder to line up and focus your shot while the IR filter is on. With the OB-Pod you can line up and focus the shot without the filter; then lift the camera off the tripod; fit the filter and return the camera back to tripod with the alignment preserved.

I can even change the batteries in my camera without changing the camera alignment but this depends on your camera design.

The way the OB-Pod works is based on the principles that:
(1) 3 points define one plane (the reason tripods are stable)
(2) Any plane section of a sphere is a circle. In simple terms a ball will sit nicely and accurately in a smaller round hole.
In this case the ball is a dome nut and the round hole is found in the middle of a particular make of furniture foot designed to protect floors. 

Step 1: Parts and Tools

To make the base of the OB-Pod I have used a bamboo chopping board (just like my copy stand). I have a penchant for using laminated bamboo; it is fairly light, strong, doesn't warp and bamboo is the fastest growing hardwood. An excellent alternative to cutting down old growth forests. I hope you can get laminated bamboo chopping board or bamboo flooring panel in your neck of the (precious) woods.
The board size is not critical but you should use something big enough to provide stability to your camera without being cumbersome. The material should be light, strong and resistant to warping and swelling.
Some of the parts are probably regional but I have included photographs so you can find substitutes or even just understand the local terminology.
The only really critical issue is that the dome nuts and furniture feet work together. I used a brand called "The Original Slipstick Gripper" but you don't have to use furniture feet many other components could be used. One untried possibility is to drill shallow over sized holes in the board and glue washers over the holes (see diagram), this should still allow the precise alignment required but I have not tested this idea.
What ever you use for the moveable holes, they must be made from a good strong hard material with a suitable sized clean edged hole that will support a dome nut. The hole should be ~70% of the diameter of the dome nut.The dome must be supported by the edge of the hole (see the cross section diagram).
The reason I didn't just drill holes in the board is so I can move the holes around while gluing to make them perfectly aligned with the 3 dome nuts after they are position locked in the "T mount". This is critical unless the holes are precisely placed the mount can jump between 2 or 3 different stable positions.

Parts list
20cm x 30cm laminated bamboo base board (I used a chopping board)
Spray Paint (not water based for bamboo)
450mm of 1" Square (1.2mm wall) Aluminium Tubing (As used for light shelving).
1 x Shelving T Joiner
3 x Shelving End Plugs
Aluminium rectangle for camera platform to suit camera (see discussion)
Book binding tape or thin adhesive rubber tape
1/4" T Nut
Short 1/4" bolt, most likely cut to suit.
1/4" 50mm long Round Head Screw
3 X 1/4" Nuts
1 or 2 1/4" Lock Washers
2 X 1/4" Washers
Bottle Cap
3 X 3/8" Dome Nuts (See the discussion about why 3/8")
3 X 3/8" 1.5" long Bolts  
6 X 3/8" Washers           
3 X 32mm Furniture feet / floor protectors (See discussion)
2 x 3/16" 38mm long Countersunk Screws
2 x 3/16" Dome Nuts
2 x 3/16" Washers
Locktite or similar thread locking compound
Araldite adhesive (not 5 minute)

Sandpaper, Hacksaw, File, Square, Screwdriver, Spanner
Drill and drill bits, Dremel, Orbital Sander

Step 2: Making the T Mount

The "T mount" is a "T" shaped assembly made from light aluminium square tubing, as used for shelving. It also uses a standard shelving "T" joiner and 3 end plugs. In practice the camera is attached to the "T mount" via an aluminium platform.The top of the "T" spans the width of the board; the height of the "T" spans the length. The photographs should make this clear. One standard 450mm length of tubing was just the right length for my 20cm x 30cm board.
The "T mount" is drilled to take the 3 x 3/8" bolts one on each end of the "T" arms, it may seem a ridiculous sized bolt in this frail tubing and I am sure that if you over tighten the 3/8" bolts you could crush the tubing. I used a thread locking compound on all the metal to metal surfaces when fitting the 3/8" bolts. This was so a firm, but not devastating tighten would ensure that the dome nuts would remain firmly in place. Use a good thick washers under the head of the bolts and nuts to distribute the pressure.
The only reason I used 3/8" bolts was so that I could use 3/8" dome nuts as the aligning legs; 3/8" dome nuts fitted perfectly in the 32mm furniture feet I had at hand. There was some vigorous argument about whether it was good to have bigger or smaller dome nuts. I suspect that 1/4" dome nuts might work with smaller furniture feet just as well but I would not go any smaller than 1/4". I have included a close up photograph of an assembled leg.

Step 3: The Camera Mounting Platform

The next step is to determine where to put the camera mounting platform. Ideally you want to get the camera centre of gravity over the middle of the "T mount", but you don't want any of the "T mount" appearing in the shot when the camera is in it's widest view setting.
I made my camera mounting platform from a stack of 3 X 80 mm long pieces of 40 mm x 3 mm aluminium strip; I needed about 9mm to allow the sun shield on my FZ50 to clear the T. You will have to design your platform to suit your camera with the attachments you intend to use. If your camera mounting hole is off-centre you may have to do some design adaption. There is nothing preventing you from drilling the T to allow more than one camera position or even another camera (T for 2 i{^_^}).
If possible it is a really good idea to avoid covering the camera battery access with the platform; I can actually change the batteries on my camera without disturbing the camera alignment.
Examine the photographs to get an idea about the platform and how it works.
I used 2 x 3/16" 38mm long countersunk screws to hold the platform in position. At first I used ordinary nuts but later I changed to dome nuts to avoid things catching on the screw ends.You will also have to drill a 1/4" hole right through for the camera mounting screw.
I put tape on the platform to give a better grip and some protection to the camera. The first tape I tried was a special soft vinyl tape but it did not stick well; I later changed it to the tried and true book binding tape.

Step 4: Making the Board

I decided to paint the board to protect the board from moisture that might cause slight dimensional changes.
Bamboo chopping boards usually are quite open grained particularly where the nodes are. I started preparing the board by filling the grain with a commercial timber grain filler (plastic wood) and sanding the board with an orbital sander and 150 grade sandpaper. After it was smooth I sprayed it with two coats of black gloss spray paint with a light sand between coats. I have found water based paint does not work well on bamboo, the paint I used was fairly standard gloss paint from a spray can.
I took the unusual approach of painting the board first; this was because it was easier to sand with an orbital sander when nothing was attached. Also the painted surface was to provide a smooth slippery surface to assist aligning the furniture feet to the T-mount while gluing.
After the board was finished I drilled and recessed a hole in the middle of the lower face of the board and drove in a 1/4" T-nut this is to receive the mounting screw from the tripod. If you have a tripod with a 3/8" thread or some non-standard size then you will need an appropriately sized T-nut.
The T-nut was reinforced by fitting a 1/4" bolt and washer on the upper side of the board. The 1/4" bolt was cut and filed to a length sufficient to engage about 5 - 6 threads in the T-nut, this leaves a generous amount for the tripod screw. 
The attached photographs should make all this clear.

Step 5: Attaching the Furniture Feet

The next stage is putting on the furniture feet. Keep in mind that they are not used for their original purpose in this project; they actually face upwards to provide holes (sockets) for the dome nuts on the T mount.
First the double sided tape on the back of the feet was removed and care was taken to make sure no residue was left. Then the 3 feet were placed on the board and the T mount was placed in position with the T nuts perfectly placed in the holes. The arrangement was slid around on the board to place the feet with equal spacing from the edges and then the position of the rear middle foot (the longer arm of the T) was marked with 3 small pieces of masking tape.
The board was cleared of parts and a smaller circle of paint was removed with a small sanding attachment in the Dremel. This was to make sure that the Araldite would stick to the bamboo and not just the paint, care was taken to ensure that sufficient painted area was left to allow the foot to slide around to allow positioning before the adhesive sets.
This first foot defines the other two in the front corners of the board, it's position is not as critical so you can use 5 minute Araldite to glue it down. Be careful not to use too much glue; if some comes through the hole in the middle of the foot it could interfere with the seating of the dome nut. Use the T mount and some weight (~2 - 4 Kg) to put pressure on the foot while it is setting.
After the first foot is firmly attached then repeat the the masking tape markers and sanding off the paint with both the front two corner feet. (See photograph). This time glue with ordinary slow set Araldite; you need time to make sure you can get both those two feet in the exact alignment with the T mount. Once you have them in position under the T mount place some weight on top; any ~2 - 4 Kg. weight will do (see photograph) make sure all the the dome nuts are perfectly seated and leave it in a safe place to set.

Step 6: Using the OB-Pod

The camera is attached to the T mount with a 1/4" screw with a bottle cap attached to make it easy to tighten by hand. (see the attached photograph). I used a bright orange cap so if I drop it in long grass I can find it easily.
First drill a 1/4" hole in the middle of the cap, inset a 50mm long 1/4" round head screw and add a lock washer. Then tighten on 3 nuts one after the other under the cap then add a flat washer. This is done so that the bearing surface is metal on metal not metal on plastic.
You may have to experiment with this setup to get it right; I had to cut the cap I used to make it less tall before it would allow just enough thread through to mount the camera.

Once you have the camera hold down screw finished and all the glue is fully cured then the OB-Pod is ready to use. Attach the board to a good solid tripod and attach your camera to the T mount. Then place the T mount and camera on the board locating the dome nuts in the correct holes. Line the tripod and camera up with your subject. and practice taking the camera off and on in one smooth movement. When you can do it smoothly take a shot; remove and replace the camera and take another shot; then compare the two images to see how well the alignment is preserved. Either use a remote lead or set the camera's time delay shutter while off the board to make sure you don't disturb the tripod.

With my Panasonic FZ50 I seem to get the best results with image stabilization turned off! I have been able to get an on-off-on replacement error of ~0.25 mm at 4.5 metres which is about 11 seconds of angle.

So far I have found only two weaknesses with the OB-Pod:
(1) You cannot point your camera up or down at steep angles.
            (The T-mount slides of the board).
(2) You do need a solid tripod; preferably without a quick release.
            (Most quick releases cannot handle the leverage of the board providing less than optimum results.)

Cool build, I'm designing something similar, hopefully building it sometime next month. My one concern on your setup is that it could get knocked over if the camera or tripod is jostled (the cupping being rather shallow). I'm toying with a clamping system, as safety wire still wouldn't help much with toppling.
Actually the camera and T mount are only on the base for the short time while I am taking a shot. I keep the strap around my neck the whole time and most of the time the camera, and attached T mount, are resting comfortably and safely on my tummy. In this position the T mount actually makes it easier to access the camera menu and change settings, the mount keeps the camera orientated while buttons are pressed.<br> The only time I have a worry about sliding is if I am taking pictures at a steep angle, greater than ~15 degrees. Even then the camera is in no danger, it just means I cannot use the OB-Pod to get that shot.<br> I am working on improvements that will solve this problem and also make the design more stable (OB-Pod Mark II ?). In fact the last few of the parts I need arrived a couple of nights ago from China.<br> Keep in mind that any clamping system has to be able to be activated and deactivated with no force or vibration. I evaluated about 5 different systems before I came up with what I am using in Mark II.<br> I hope to have it up soon so perhaps you can take advantage of the new design.<br>
Nice photos ;) Very well made ible :D

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