My system so far

Rylee Isitt · Post by **Rylee Isitt** » Fri Apr 13, 2012 6:08 pm

Hi everyone. Recently, I've taken on the expensive project of building a table-top macro and microphotography system. I have a few microscopes (a compound and a stereo), but I prefer the modular and versatile nature of the approach I've taken. And I see several other users here have done similar things.

At the moment, what I'm working with is something of a beast, to put it lightly.

I built a copy stand out of Lego. It's driven by a stepper motor and micro-controller for automated focus stacking. To make up for Lego's lack of strength in some cases, I've used metal drive shafts. The standard plastic ones flex.

Not shown here is twin flash (Canon MT-24EX) that I use for lighting. I mount the flash heads on flexible arms attached to a tripod and connect the unit to the camera with a off-camera flash cord. I plan to use pocket wizards in the future. The flash is always used in manual mode - TTL is unreliable for this kind of work.

The optics are fairly simple, since they're based on finite (160mm tube length) objectives. I'm currently using some low-end no-name objective lenses.

Here are the optics and adapters used:

From left to right is a T2 to Canon EF adapter, a VariMag projection body, the VariMag optics module, a M42 to T2 adapter, an M42 bellows, an RMS to M42 flat adapter, and finally the RMS-threaded finite objective. If using low magnification, the entire VariMag assembly and its optics module can be omitted. At higher magnifications, it is required to prevent vignetting.

I am not sure if the VariMag optics module would act as a tube lens for infinity corrected objectives. I'm guessing not.

The stacking controller was a decent project all to itself. It's based on an Arduino UNO micro-controller and a stepper motor controller. It can also trigger the camera shutter automatically. Once you set the start and end position, tell it how many steps to use and how long to wait between them, it's fully automated.

If anyone has any questions, feel free to ask. However, I'd like to start with a few of my own:

What would you recommend as a good high quality, but reasonably easy to find finite RMS-threaded objective lens? I'm currently looking for Nikon CF Apo Plan lenses from 4x to 40x. These are hard to find in Canada (I'd have to pay duty from other locations). I'd also like to use the objectives on my compound microscope, which is why I'm currently avoiding looking for M lenses. That said... I may go that route eventually.

Finally, although the Lego copy stand looks amusing, I'd prefer to use a real, more sturdy copy stand, and simply attach the Lego gear train to it and the focusing rack. Any suggestions on a good copy stand to look for? Although I'd like to make one out of wood, I don't have a shop and am currently living in a student residence.

rjlittlefield · Post by **rjlittlefield** » Fri Apr 13, 2012 8:41 pm

Rylee, welcome aboard -- your system looks great!

If using low magnification, the entire VariMag assembly and its optics module can be omitted. At higher magnifications, it is required to prevent vignetting.

What's causing the vignetting? Are you using a full frame sensor and the corners are getting shadowed by that T2 adapter?

What would you recommend as a good high quality, but reasonably easy to find finite RMS-threaded objective lens? I'm currently looking for Nikon CF Apo Plan lenses from 4x to 40x.

Hard problem. See HERE for some info at 4-5X. But none of those lenses except the last combo is in the class of a CF Plan Apo, and the combo is not finite. At 10X, the Nikon CF N 10X NA 0.30 is a reliable performer, but they don't turn up often these days. You might also consider a CF E 10X NA 0.25 or its kissing cousin from Edmund Optics, as described HERE. That thread also discusses how those the 10X NA 0.25 and 10X NA 0.30 compare. There are tradeoffs, each lens better in some ways.

--Rik

Rylee Isitt · Post by **Rylee Isitt** » Fri Apr 13, 2012 9:37 pm

Thanks for the suggestions on those lenses, Rik!

I am not entirely sure as to the cause of the vignetting. I'm using a 1.6x crop sensor and the diameter of the openings in the adapters should be more than adequate.

I am definitely lacking on the optical theory here. My understanding is that the objective is projecting a light cone, and as I elongate the bellows I am narrowing my field of view in towards the center of the light cone - so if the entire field of view shows no obvious vignetting, I don't see why narrowing in on the center should change that.

The VariMag is a photo eyepiece which I purchased some time ago for doing microphotography through my compound scope. I used it in this setup because it addresses the problem, but I'm not entirely sure why. Based on my experience trying to mount my camera to the scope without a photo eyepiece, I can tell that the VariMag is necessary to avoid vignetting when imaging through a c-mount. That makes sense, because the c-mount is a pretty small opening.

If I had to guess, there's probably some part of my bellows that starts to cause a problem as it is elongated. Still, that doesn't make much sense to me. Looking through the bellows, elongated or otherwise, there is no visible obstruction.

I am pretty stumped, to be honest.

Edit: I just realized that "vignetting" might not be the technically accurate term for what I'm seeing. I'll post a photo soon.

rjlittlefield · Post by **rjlittlefield** » Fri Apr 13, 2012 9:50 pm

To investigate the vignetting (if that's what it is), just remove the camera while leaving everything else in place right down to the last adapter. Look down through the center of the setup so you can see the whole circle of the objective, then slide your head sideways until something starts to cut off the circle. Whatever that something is, that's your problem.

--Rik

Rylee Isitt · Post by **Rylee Isitt** » Fri Apr 13, 2012 11:11 pm

Thanks Rik!

I am somewhat embarrassed to admit that the problem doesn't actually exist at all. Following your advice, I could see absolutely nothing that cut off the image circle - it actually got cut off by the objective barrel first, indicating that if anything, I should be seeing vignetting at the lowest magnifications due to the lens being unable to deliver a wide field of view.

So that leaves a bit of a mystery. I definitely saw vignetting with this system two weeks ago, and the VariMag did make them go away. The most likely explanation was a misaligned M42 thread on the bellows, leading to a slightly crooked connection with the camera. It is fairly easy to misalign this adapter, if you don't fully tighten the retaining screw. At low magnifications, this would manifest as tilted focus plane, but I was shooting larger, 3d objects that day, so might not have noticed. At high magnifications, however, the crooked adapter would be farther back from the objective lens and I suspect this would exaggerate the effect of the misalignment.

So, that's that. No need for the VariMag in this setup at all.

I can't believe I purchased an adapter from halfway around the world to solve a problem that didn't exist!

The shots below were taken with the setup pictured in my first post, minus the VariMag. The slide was raised above a diffused LED backlight. The first two were taken with a 4x objective, the second of which was at the maximum bellows extension. The third was using a 10x objective lens, also with the bellows as maximum extension.

Yup, I need planoptic objectives.

rjlittlefield · Post by **rjlittlefield** » Fri Apr 13, 2012 11:27 pm

Rylee Isitt wrote:Yup, I need planoptic objectives.

Even better, you need focus stacking. As the author of Zerene Stacker, I'm a great fan of that approach.

It's also much cheaper than the VariMag, and more robust than plan objectives -- assuming of course that your subject doesn't move!

--Rik

Rylee Isitt · Post by **Rylee Isitt** » Fri Apr 13, 2012 11:38 pm

I do focus stacking and have that nice automated system for doing it, but it doesn't have a step size fine enough to do stacking with slides. I could change the gear train to make up for that, though.

For microphotography, I intend to use my modified compound scope, and attach the stepper to the fine focus knob. I removed the trinocular head and have a universal dovetail to M42 adapter pair, so the light does not get split three ways and there are no optics other than the objective lenses. Unfortunately, I need to convert the female/internal M42 thread to an external/male M42 thread, and it seems like finding a male M42 coupler is going to be difficult! So for now, I've been doing microphotography with my Lego setup, which isn't quite what I intended it for.

For stacking, I've been using Photoshop CS5. It's stacking works amazingly well - far better than Helicon Focus in my experience. I like how it blends frames, in particular. I haven't tried Zerene Stacker. Gotta say, I'm a fan of fiddling... so perhaps I will give it a shot one of these days.

rjlittlefield · Post by **rjlittlefield** » Sat Apr 14, 2012 12:05 am

Rylee Isitt wrote:For stacking, I've been using Photoshop CS5. It's stacking works amazingly well

It depends on the subject. See for example Image comparison of ZS and PS CS5 on deep high mag stacks. But certainly if it's working well for what you're doing, keep using it!

--Rik

Rylee Isitt · Post by **Rylee Isitt** » Sat Apr 14, 2012 12:24 am

Rik,

About your lens suggestions, I have the MP-E65 and use it extensively for sub-5x work. It's one of my favorite lenses, and I take it into the field quite often. The increase in sharpness seen with the CFI and 100mm combo is tempting, but the tradeoff would seem to be a lack of versatility: the MP-E65 can range between 1x and 5x, while the CFI+100mm L approach appears to have a fixed magnification.

Anyway, you've given me something to think about. If I bought the 100mm L, I'd also have a pretty awesome performing lens for 1:1 work... but... so many lenses!

That 10x Nikon Achromat lens at Edmund Optics is currently listed at $78. That's essentially what I paid for my no-name 10x objective that I currently have. I might have to go for it.

Again, thanks for your input! It's given me a lot to think about.

Rylee Isitt · Post by **Rylee Isitt** » Sat Apr 14, 2012 12:33 am

Rik,

Yup, PS CS5 does mess up stacking, sometimes badly, depending on the subject. When it works, it works very well, and when it fails, you often have to spend time painting in custom masks.

I have not tried it for magnification beyond 4x. The result you got is worse than anything it's ever done to my stacks - it seems to have had problems aligning the frames, and that led to more problems when it tried to blend them. Try allowing geometric distortion.

That said, if you have to fiddle this much, and if Zerene Stacker works more or less out of the box, then that's certainly points in Zerene Stacker's favor.

g4lab · Post by **g4lab** » Sat Apr 14, 2012 11:29 am

I always get a a pleasant burst of enjoyment seeing people make things like this out of Legos. I myself am of an age when it would have been Meccano rather than Lego (Erector Sets in the USA)

I can't remember what similar hobbyist constructions I have seen, but I know that while looking at your wonderful set up, I was asking myself(for at least the third time) , so I will ask you : "I wonder whether he glues those Lego blocks together , either with super glue or with styrene solvating glue or something else, similar??"

Rylee Isitt · Post by **Rylee Isitt** » Sat Apr 14, 2012 11:46 am

g4lab,

Haha! No glue at all!

Okay, I'll admit to one exception: I had to attach a gear to the stepper motor using epoxy, because the friction fit wasn't tight enough and it was slipping on the drive shaft.

Everything else is reinforced with friction pins, a standard Lego Technic component. Notice how I use those bricks with the holes in them, and how they over run perpendicular to each other? The perpendicular bricks snap into the friction pins and hold everything together.

You could throw this thing out the window and it would probably hold together. The weakest parts are the eight connections between the legs of the stand and the wooden "adapter" for the focusing rack. I plan to reinforce those further, but need to buy more Lego parts before I can do that.

It doesn't flex nearly as much as you might think. The main problem is vibration. I have it on rubber feet, which I think was a mistake, and I live on a student residence, so someone is always running a subwoofer or stomping around heavily. And the building isn't exactly rock solid...

elf · Post by **elf** » Sat Apr 14, 2012 12:26 pm

Rylee Isitt wrote: It doesn't flex nearly as much as you might think. The main problem is vibration. I have it on rubber feet, which I think was a mistake, and I live on a student residence, so someone is always running a subwoofer or stomping around heavily. And the building isn't exactly rock solid...

Putting the current setup on a block of granite from Enco mounted on Sorbothane feet would help quite a bit. They do have free shipping occasionly so it can be fairly inexpensive.

I haven't used any products from http://www.vibrationmounts.com/, but some of the techniques would be easy to create with limited shop tools. I like the Brillo pad best

Rylee Isitt · Post by **Rylee Isitt** » Sat Apr 14, 2012 1:05 pm

Interesting idea, elf

That's what the lab folks do to prevent vibrations from messing up the readings on the lab balances.

I'll have to try that. Thanks for the tip!