Focusing rails, (yet again!)

[Charles Krebs]

In this recent thread we once again hashed over rails. I had mentioned that my favorite was the Novoflex Castel L (discussed in some detail here.)

I also wondered if a new, very cheap, Chinese one (like ebay 200436163630) would be of any use at all. Well, let's dispense with that first. With a few improvements it could be quite usable, but as it is now forget it. Fairly crude but serviceable construction, it's biggest failure is that there are no dissimilar metals or plastic/delrin type surfaces for sliding. As a result when a SLR camera is mounted it it feels rough and sticky. Might be OK for a very lightweight P&S if the budget were really tight.

On a recent outing I used the 65MPE and the 100/2.8 with the Novoflex rail. No problem with the 100/2.8, but with the 65MPE at 3X and up I did have a little difficulty. When the rail gets wet/dirty it can get just a little "sticky" and the fine increments needed at those mags were a little tricky. Not impossible by any means, but not as smooth as I would like. The other thing I noticed about using it for stacks had to do with the Canon 50D. I've come to really like using the extremely low vibration live-view mode. Before, with the (non Live-view) 5D, I would look through the view finder as I moved the camera to the next focus step. Simple and easy to do. When using live-view outside, I realized that it's pretty hard to judge the focus step by viewing the back screen (seems like it should be easier, but it's not!). It's a pain to "exit" live view just to get a look through the viewfinder to set the next focus position, and then go back to live-view. Something where I could easily "dial in" a focus interval without looking through the viewfinder, and that would be more "waterproof" would be better for the 65MPE in really wet environment like the rain-forest.

I remembered David's ("dmillard") very nice implementation of a Velmex slide. When I saw it I thought it was a great usage. Then, when I read on the Velmex site how they had even been used under water (!), I decided to finally fix up a Unislde I had picked up on eBay some time ago. Following David's lead I attached a long AS plate to the bottom and an AS clamp to the top. My slide did not have a an engraved knob, so I made up a "dial" and attached it to the knob. I marked this dial so that it would be easy to set 1/8 turn increments for lower mags, and then placed "tick" marks at 5 degree intervals. This slide has a 20 tpi lead screw. So every "tick" mark moves the slide 0.017mm. (1/8 rotation moves 0.156mm). When using the 65MPE at 5:1 and at (marked) f4 it needs to be rotated three "tick" marks between steps. At 1:1 and f8, I need to make a 5/8 rotation between steps. So this thread pitch works out pretty nicely with the range of the 65MPE.

I'm not that crazy about "roughing in" the focus by loosening the AS clamp, but as long as the plate you attach has "stops" at each end it's not too bad. Other than that is seems pretty nice. David's shots of his are nicer than mine, but here are a few shots with the 65MPE attached:

[augusthouse]

Nice

I like your customised dial Charlie very nice!

Any tips in regard to attaching the AS clamp and AS dovetail to the Velmex? Was the RRS clamp good to go as/is, or did you need to adapt it to line up with the holes on the Velmex? As David mentioned, finding a suitable AS clamp is tricky.

Just for the record, the 20tpi leadscrew can be swapped-out for a 40tpi and an engraved graduated knob or drum dial can also be purchased from Velmex.

Some more info on the A25 series UniSlides at link below:

http://www.velmex.com/manual_cross_sect ... eries=2500

Craig

[Charles Krebs]

Craig,

I was just about to drill and countersink two mounting holes in an older RRS clamp when I took a look at my RRS lever clamp. It was one of those serendipitous things... it already had two mounting holes that were spaced, on centers, exactly the same distance as two of the 8-32 threaded mounting holes that were already on the Velmex platform. You can see them in the picture below (here the clamp is attached to the Novoflex rail). So that was a simple matter.


There are plenty of non-skeletonized AS style clamps out there. (Mine are all older so they have solid bases). So even if I hadn't lucked out with the clamp I used, it would not have been a big deal to drill a couple mounting holes into a clamp.

I already had a long AS plate, so I drilled and tapped two 1/4-20 mounting holes into the Velmex base. All in all pretty simple adaptation.

I've got another slide with the 40 tpi lead screw. But I think that for my purposes here the 20 tpi is a better fit. It's easy to set the finest increment I need with the 65MPE. And should still be quite usable with the 100/2.8 (without having to spin the knob around forever at the lower mags).

[Stephane Savard]

Charles,

Thanks for the advice on the cheap chinese rail!

[DQE]

I really enjoyed your well-illustrated post, with its detailed discussion.

This got me to thinking again about the StackShot automated rail system, to be released next month I believe. I now fear I will have trouble resisting becoming an early adopter!

I think all one needs to do is to attach a good screw-type quick-release to the top plate of the StackShot system and fire away. The quick release is important since I believe that one will need to rapidly switch between taking single photos and trying for a stack during a typical summer day. The extra weight of the StackShot is just enough to want to get rid of it when not needed.

Based in part on your post, the StackShot's approximately 10 micron step size seems to be small enough for 5x with the MPE-65 lens, pending verification with real photos.

The stressful part may be when it quickly becomes obvious that having an automatic stacking device doesn't automatically set up the lighting, the bug position, camera position, etc, etc. In other words, one will still need good composition skills and good lighting techniques to get high-quality automatically stacked macro photos. Hopefully the system will at least get around having to develop and use very fast manual stacking skills while simultaneously managing the other factors!

[bklein]

Hi Charles,
Regarding the cheap Chinese slides....
For a DIY guy like me would it much trouble to make the Chinese slides function ok? What would you think necessary?
Are all the ebay offerings of these identical or is there some variation?
Thanks,

Barry

[ChrisR]

Does anyone know, or could someone kindly measure, the angle of the dovetail on the AS system?
I'm thinking of 1/2" Routers, dovetail bits... Aluminium, acetal, lignum vitae, teak...

[AndrewC]

Does anyone know, or could someone kindly measure, the angle of the dovetail on the AS system?
I'm thinking of 1/2" Routers, dovetail bits... Aluminium, acetal, lignum vitae, teak...

I sometimes cut AS compatible dovetails - just use a V-groove bit with 45degree blades. The angle really isn't that critical IMHO. For stress relief it is a goo didea to round out the bottom so I just run a bullnose along that.

A few years ago I looked at buying some AS stock bar in T6 aluminium alloy bar. Cost wasn't too much per cm but minimum order was 10metres. If enough people are interested it might be worth buying a large order and divvying it up. Unfortunately my minimill isn't up to cutting large quantities otherwise I'd do it.

Andrew.