My rig. Tips on lining up subject movement?

[lauriek]

After a picture post turned into a bit of a Q&A session, Rik sensibly suggested I post this over here, so here goes!

My current macro setup which is far from ideal, consists two components, the camera 'unit' and the subject 'unit'.

First the camera unit. This consists (from the bottom up) of a tripod, a ball head, a QR plate, an OM Auto bellows. In this picture the camera would mount on the right hand side, and the macro flash head is stuck on the left hand side with blue-tac... On the left of the bellows is a reversed OM50/1.8.




Second, the subject unit. This is an old Prior micro-manipulator with fine movements in X, Y and Z axis. This is normally stood on a small piece of furniture to bring it up to a sensible working level, while stil low enough for decent tripod stability. The legs of the tripod are not extended at all...

As I currently use it this is the Top down view:



As currently used this is the Side view:




At this point I normally botch the insect mount by wedging the rear end of the bug subject in a tiny piece of folded cardboard, and then pinch this in the croc clip on the manipulator. (This does occasionally result in the bug 'pinging' out!)


My method of lining up the stack goes like this - I start off with the bellows at minimal extension (and the lens set to say f5.6ish but the bellows switch not holding the aperture closed - so the aperture is wide open for viewing), and I move the tripod around until I find the subject in the viewfinder. I then center the subject in the viewfinder by moving the subject around with the manipulator controls. Then I extend the bellows to get the magnification I require, and re-focus with the focus rail, and re-center with the manipulator. I then adjust the focus through the bug to ensure I'm framed correctly for all stages of the stack. (Having learnt early on its easy to get too close on the front of the stack so that by the time you get to the back you've chopped off loads of the interesting bits at the front!)

Finally I return the focus to the front of the bug, do some test exposures, get that to my liking, play with the background etc, then do the slices, by simply moving the camera/bellows/lens on the focus rail. Doing this seems to keep the slices fairly well positioned (in relation to each other) so the stacking software can put everything together without too much trouble.



This is fine up to a certain level of magnification, but beyond thatthe problem becomes moving the focusing rail by small enough increments to get everything in focus.

Now the thing is, this manipulator has one extremely fine movement. On the vertical axis (in my current orientation) there are two control knobs. The large black one is a coarse control and can move the whole thing up and down 2-3 inches. The small black knob near the base is the fine vertical control knob. It is marked with 25 units, and can make 10 full rotations. A full 10 rotations moves the subject somewhere between 1-2mm up or down. Hence one full rotation of this knob moves the subject 0.1-0.2mm, and 1/25 of that is 0.004mm-0.008mm (I must work out exactly how much movement that does have to avoid these loose estimates!) - anyway I reckon I could reliably move it 1/2 of one unit on this scale, so if I could line the subject up with this axis of movement then I could reliably move the focus plain by 0.004mm or better. Which I suspect is a hell of a lot better than the bellows focus rail can do. The problem I have is how do I line this lot up so that the subject moves directly towards the centre of the lens?!

Does this all make sense? And if so any tips on ligning the subject movement up with the centre of the lens so that using the fine control moves the subject perpendicular to the plane of focus?

Thanks for reading!

[rjlittlefield]

Laurie,

These photos help a great deal -- thanks.

Here's what I recommend...presuming that you have a few basic tools...

Ditch the tripod -- it'll cause you nothing but grief.

Obtain for yourself the following parts:

1 large piece of plywood or fiberboard, preferably 5/8" or thicker.
An assortment of wooden blocks.
1/4" x 20 bolt (or whatever fits the bellows mounting hole)
Assorted wood screws

What you're going to do is this:

. Lay out positions so that you can proceed as follows...
. Fasten the micromanipulatior to one of the wood blocks, then screw the wood block onto the plywood, oriented so that the fine movement is parallel to the plywood and pointed in the general direction of the camera.
. Drill a number of holes through the plywood that will allow the bellows to mount in a range of positions corresponding to the magnifications that you care about.
. Fasten a few more blocks to the underside of the panel as needed to elevate it, to provide space for the bellows mounting bolt.
. Loosely fasten the bellows to the plywood using a bolt from underneath.
. Use a square or trial-and-error to rotate the bellows so that its axis is parallel to the micromanipulator's fine movement direction.
. Tighten the bolt to lock everything in position.

In use, you'll move the standards along the bellows to get the magnification and focus that you need, possibly moving the bellows to another mounting hole if necessary.

Once you get the standards placed, then set some wedges under the front and back of the bellows rail to further stabilize it. Be sure not to pry the bellows out of level when you do this -- you're just trying to get the rig stable enough so that the vibrations from shutter movement will be relatively small and more importantly will damp out quickly.

Depending on how things are sized and oriented, you might need to raise the bellows above the plywood panel. But try to avoid that because it'll cut into your stability.

After this is all set properly, then framing is done with the coarse controls on the manipulator, and stacking with the fine control.

One minor refinement... Instead of an actual bolt, I like to use just a chunk of threaded rod plus a wingnut. That way I don't need tools to rearrange the setup.

Sound like a plan? What have I overlooked?

--Rik

[Graham Stabler]

You might start with a spirit level so you only have one angular axis to align.

You could place a flat object on the front of the stage (coverslip with some black marker on it), then adjust until the whole thing is in focus, assuming it is perpendicular to the axis of motion (it should be) that would work. Then remove, insert insect and adjust position (not angle).

Does everyone have one of those Prior manipulators? I do and I keep seeing them around. You could add a bigger knob and dial for finer adjustment, perhaps use a protractor, you can soon relate degrees to movement or at least produce repeatable steps.

Graham

[lauriek]

Thanks so much! That does indeed sound like a plan! Guess I'll find out if you've forgotten anything when I come to bolt it all together!!

I'd spotted the tripod was a problem but I hadn't worked out what else to use, I have a little Hama table clamp but it's not sturdy enough to hold this rig...

I'll definitely add a spirit level to the mix!

Personally I only discovered such things (micro-manipulators) existed last year when I spotted one on ebay, at that point I'd been considering getting one of those little 'helping hands' stand things - when I spotted the Prior it just jumped out at me as ideal for accurately controlling the position of the subject.

[puzzledpaul]

Considering the (short) working distances involved, the drilled / tapped holes at each end of the main rail could also be of use for 'extending the axis'?

(I've not used same in this type of setup - but have for others - esp. as the end faces are also probably - fairly - but not precisely - square with the rail)

Good luck

pp

[Graham Stabler]

If you do as Rik suggests (I was writing as he was posting) and use a strudy base plate and mount to that then that will already remove the angular degrees of freedom that you don't need. Sounds a great idea and you will only have to align it once which means you can just move the object back and forth while adjusting the angles and then tighten up.

Graam

[johan]

I am glad that I came across this. My setup as of 2 weeks ago is very similar to Lauriek's very old one. Unfortunately this is literally the only space in our house but at least I have an idea of a progress path now, get it all onto 1 piece of wood. Note the obligatory growing collection of diffuser things perched on the printer!


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