Bought an Old Carl Zeiss Jena focus block

[cadman342001]

I just picked this up on ebay for 40 euros, typically on impulse but it is hard to find this stuff in Oz (or at least I can't find it but I do live in the top right corner of Far North QLD)

I currently have a basic rig - 200mm f4 with reversed 50mm (old nippon kogaku mf lenses) on a proxxon KT70 table but I just know I'm gonna get carried away and get a microscope objective and so will then need something more accurate.

(pics of current set up in beginner's macro section)

Did I just waste my money ? Honestly, I'd have it as an ornament it looks that nice

Says it's in good order, 22mm coarse focus travel, 1.8mm fine focus, 0.002mm per interval.

http://www.ebay.com.au/itm/131412524981 ... 1439.l2648

Thanks

Andy

[ChrisR]

I happen to know another member just turned it down because of the 1.8mm fine focus travel .
That means that when you hit the end of the fine travel, you'll have to back all the way back on the fine, then use the coarse adjustment to go forwards something less than 1.8mm, then use the fine again going forwards. That's not ideal, because it'll be tricky to pick up where you left off. You will not want to overlap, or leave a gap.
It's definitely doable though, and you can simply leave overlapping frames out of what you stack.
2 microns is fine enough for just about anything.

[Koorosh]

Ah yes, I was very excited about how fine the adjustments were, but a bit gutted when I found that the travel was pretty small. I imagine it would be amazing for anything very small, i.e less than 1.8mm deep. Not so easy for anything else, but as Chris said, do-able, just a bit annoying.

Good luck with it, and look forward to anything small you image

To that end, mites might be a great subject for that! I'll be having them as subjects once I get set up.

[cadman342001]

Thanks chaps, well, paperweight it is !

Only joking

So, thinking about it, how's this -

Use the fine focus until it runs out, then use the coarse focus to move 1.8mm (or preferrably a little less to allow for overlap) forwards, and then use the fine focus BACKWARDS for 1.8mm, then move coarse focus to move another 1.8mm (or a bit less) forward and use the fine focus forwards again.

Will that work ? Would Zerene cope with this and not get confused?
Could I stack each "set" of images in Zerene and then take the resulting stacks and stack them in Zerene ? Does that make sense?

[Koorosh]

For the backwards focussed ones you could reverse the order of them possibly by date taken? Then move them into a folder possibly. Whether or not they will be automatically reversed again I'm not sure. Couldn't say for Zerene whether that would confuse it, but Rik is the man for that. Alternatively paper weight Or just use for really small things with a microscope objective.

[rjlittlefield]

Any stacking program would be very likely to get confused by trying to process the whole batch at once. What happens is that little errors in alignment tend to accumulate so that by the time you've done positions X, X+Ns, X+(N-1)s, X+(N-2)s, etc., all the way back to X+s, there's basically no chance at all that the frames that are logically one step apart at X and X+s would perfectly line up with each other. I know people who've tried things very much like this, and they definitely were not happy with the results.

Stacking each set separately and then stacking the stacks would be a better bet, but I'd still bet against it. I've never tried that so I don't know how bad the problems will be, but I do know the general nature of the problems. Again, small errors will add up so that the overlapping portions of two substacks that are processed separately will end up having slightly different geometry. It will be as if the subject changed shape slightly between the two substacks. When those two substacks are merged, you're very likely to get some unpleasant ghosting in the transition zone.

--Rik

[cadman342001]

Ah well, thanks for the info Rik.

So looks like 4X set up using coarse focus and then 10X with objective using fine focus for tiny critters less than 1.8mm depth ?

or should I stick with the proxxon KT70 for the 4X and 10X stuff ?

[rjlittlefield]

The Proxxon will be workable but fiddly with your 10X. DOF at 10X is only about 0.008 mm, about 3 degrees of rotation at the Proxxon's 1 mm per turn. If you want to do that, I suggest mounting a larger dial on the Proxxon so that it's simpler to read, simpler to turn.

If it's not too much trouble to swap focusing mechanisms, then I'd really recommend the focus block whenever its fine travel is enough. One option you might consider is to stack the positioners -- fasten the focus block to the Proxxon and the camera to the focus block. That way you'd always have the long travel of the Proxxon at 1 mm per turn, plus the short travel of the focus block at 0.2 mm per turn, no swapping required.

--Rik

[cadman342001]

Yeah that could work and I'm sure it can't be too hard, I have various hammers, duct tape and glue

[rjlittlefield]

I generally use carriage bolts, nylon thumbnuts, and some steel straps with holes bored in them. Duct tape works OK at low mag, but I haven't used that at 10X for years.*

--Rik

* In figure 6 at http://www.janrik.net/insects/ExtendedD ... summer.htm, the objective was duct-taped to the end of the bellows.

[Chris S.]

I would suggest drilling and tapping holes and using machine screws, perhaps in combination with inexpensive (and easy to work) flat or right-angle aluminum stock to make adapters. For parts that will never have to come apart, a good two-part epoxy is handy.

But I'd very strongly suggest using that focus block for something other than focus stacking, which will almost surely be a painful experience. The block's coarse movement might make it a nice gizmo for adjusting your subject position sideways or up and down (assuming a horizontal rig).

Stacking positioners, as Rik suggested, can be a huge help in any macro rig, even if you get a block with a long fine-focus range. My focus block is mounted atop a Velmex Unistage with the RapidAdvance feature. The Velmex lets me quickly move the focus block fore and after to wherever I want it for a particular subject and optic. It also lets me pull the camera assembly away from the subject to change lenses without bumping subject or lighting gear, then slide it back in precisely registered to where it was before. Proxxon would work very well for this, I think.

--Chris

[steveminchington]

Yes, I made a similar 'mistake' when I bought a Leitz Dialux stand for the focus block. When I got it, I discovered it only had 2mm of travel for the fine focus. I had studied drawings of the Ortholux focus mechanism as I couldn't find anything on the Dialux, and that had a full range of fine adjustment. I assumed it would be the same for the Dialux... wrong!
It is restricted because the fine focus is operated by a cam which only has a limited travel.
The more expensive models have a clever planetary gear system which can either work 'straight through' for coarse movement or 'roudabout' for fine movement which means you can chop and change between the two gear ratios where ever you are on the slide.
As for your Zeiss focus block Andy, another option would be to remove the fine focus mechanism and couple a small reduction gearbox (with a 1/4" or 6mm dia. input/output shaft) to the coarse focus shaft. A worm drive gearbox will give a significant reduction ratio and they are not too expensive to buy.

[Koorosh]

The Proxxon will be workable but fiddly with your 10X. DOF at 10X is only about 0.008 mm, about 3 degrees of rotation at the Proxxon's 1 mm per turn. If you want to do that, I suggest mounting a larger dial on the Proxxon so that it's simpler to read, simpler to turn.

Question: with a linear stage that has a minimum increment of 0.01mm, would you have to use it at half increments then? Is that difficult to do or fairly straight-forward?

[rjlittlefield]

Question: with a linear stage that has a minimum increment of 0.01mm, would you have to use it at half increments then? Is that difficult to do or fairly straight-forward?

Sure, half-increment or whatever is needed. The screw is continuous, so you can turn it by however much you need. With a manual dial, the limit is a matter of ergonomics -- whether you can see what needs to be done, and whether your fingers can make a movement that is sufficiently small. Putting on a larger dial addresses both aspects.

--Rik

[Koorosh]

Ok thank you