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
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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