November 4th, 2009 by bobble

A couple of years ago I got into making stereograms. I saw it in a how-to book and thought that it was pretty cool! I didn’t realize just how easy it is to create stereograms. All you have to do is take two photos about 3-inches apart and use software to merge the right/left images together.

Cross your eyes to view it.

Taking the Photos
with a single camera, you are limited to taking static pictures. There can’t be any moving objects; cars, blowing trees, flying mommy-bombs, etc. if you look closely in the above stereogram, something had moved near the foundry. It was a windy day. It creates a double image which you don’t notice right away but then try focusing on it.

Get about 6-8 feet from your subject and take one picture. Shift your hips to the left or right a couple inches while keeping the camera steady. Keep the lens parallel to the first shot. Take the second picture.

One In Thirty Rule
the distance you move, or lens separation, is called the stereo-base. In order to take decent stereo photos, distance to the nearest subject should be approximately 30 times the stereo-base distance. This is called the “one-in-thirty rule”. Our eyes are about 3 inches apart. This would mean that the nearest subject should be roughly 8 feet away.

I use Stereo Photo Maker (click here) to create stereograms. It has functions to help correct alignment problems. Almost every stereo pair I’ve taken has alignment issues. I might’ve tilted the camera or moved it vertically too much from the first snapshot. This software will help make it more goodly. I’ve built a tripod mount for sliding a camera back and forth. I found that just shifting your hips, keeping the camera steady, and using this software is good enough… you won’t notice the difference.

Viewing Stereograms Without a Viewer
Bobble no like anaglyph 3D pictures. It’s those 3D pictures where you need red/cyan glasses to view them. The colors get all messed up. I prefer “freeviewing” without glasses or viewer. There are two ways of freeviewing stereograms. It depends on how the images were joined together. If the right eye image is on left-hand side of the stereogram then you need to cross your eyes to view the image. The size of the photos are quite large, I think its best to use cross-eyed viewing.

If the right eye image is on the right-hand side of the stereogram, then you don’t cross your eyes. You stare past or through the plane of the image. When you do this correctly each eye will see its intended image. This is called parallel viewing and for some people it’s a little harder to master.

In both methods you’ll end up seeing a third image that appears between the two photos (called the cyclopean image). That’s where you focus your attention. Eventually your brain locks in on this virtual image and then things start to stand out.

Some people have difficulty seeing 3d stereograms. It’s not unheard of for people to get headaches. I recently ran into my own problems and had an eye cataract removed. Now the only way I can freeview is if I’m wearing a contact lens in my good eye and wearing reading glasses. Sucks to be me.

What’s strange is if you accidentally swap the images or cross your eyes at a stereogram that is meant for parallel viewing. The cyclopean view looks 3d-ish but in a weird way like the image is inside out. When in doubt, try parallel and cross-eyed viewing to see what looks correct.

Some Guidelines
when taking stereograms photos:
* Everything in the picture should be in focus.
* The depth of focus should be large as possible.
* Avoid dark backgrounds
* Avoid excessive moving subjects like blowing trees or clouds.
* Follow the one-in-thirty rule.
* Keep the cameras level to the ground. Avoid tilting.

Stereo Camera Rig in Stereo!

Another cross-eyed stereogram. It’s a little easier if you have two cameras and rigged them with a dual trigger mechanism. Yes? Yes!

Dig the BMX bike peg for the handle! And toggle switches!?!

Discernibly Awesome Aluminum Casting

October 19th, 2009 by bobble

Had fun last weekend i though i’d try this again. [See this thread for bobble’s previous progress]

The Setup
Same configuration but had some new tins… ms. bobble got these tall tins used for olives, courtesy of seward coop.

Molding Sand
I’m using silica sand and bentonite clay. It seems that bentonite isn’t very common. Some people will use ground up cat litter because it has some bentonite in it. Fortunately i was able to find a local source – I got bentonite from minnesota clay co. in edina. I got a 25 lb box,  it’s a powder and it is really fine… so fine that it some with a material safety datasheet with warnings about cancer. I worked outside and held my breath to avoid breathing it. don’t remember the exact proportions… i made small batches and just threw them into a pail when they felt right. I got the sand at home depot.

Tourettes By Proxy
my neighbor had the windows open. i heard him yelling, “efff!! EFFF!!! YOU EFFERS!!! NOOOOOooo!!!”. at first i thought he was yelling at his kids then i realized the vikes were playing. i can only handle the vikes so much. go vikes.

anyways, great day to be outside! i was doing double duty — filling the crucible with aluminum and then pausing to fill the foundry with charcoal. i was melting cans and some aluminum pieces a buddy donated. whenever the flames weren’t roaring like a blow torch i’d toss in more charcoals into the foundry. the crucible would occasionally shift inside the foundry. three times i lifted the crucible out and put more charcoals at the bottom of the foundry. after the cans were all melted, i shut off the hair dryer and pulled out the crucible. it felt heavy and i was a little nervous handling it. i tried skimming off more crud with a spoon.

when i first poured the aluminum the sprue filled up quickly. initial thought was the sprue choked and that there’d be some defects. with the remaining molten aluminum i tried making ingots. first poured into an old muffin pan. i also poured some into a tin can. grass was smoldering.

Casting Of Discernible Awesomeness
after about 1/2 hour i dragged ms. bobble outside to see me open the mold. i lifted the cope all i could see was the scorched sand on the drag. YES! i flipped the cope over and the casting was alll filled in, NO DEFECTS!!! OOH RAH!!!

the casting was still hot. picked at it with a tool to dislodge the sand. some sand is bonded to the tips of the hersey kisses which is extra fine by me. makes the points sharper and likely to gouge the hell out of someone’s snowboard or skis. the bottom was flat but has a rough texture. total weight including sprue is 12 ounces.

the muffin pan had melted underneath. uhh… whoops.

i tore open the can that i poured aluminum. bobble make wheel! weighs 9 ounces. on the top of the pour, the aluminum has a rough surface like pumice. the edge and bottom are smooth. there are tiny little holes from hydrogen bubbles i guess.

High Five

here it is again. my only complain is i wish that the surface was a wee bit smoother.