DIY LensAlign Clone Tutorial

I liked the LensAlign Pro focus testing tool that was mentioned here a while ago, and particularly, the camera/target alignment system. But (with all respect to the inventor and manufacturer) at $180 or so, it strikes me as wildly overpriced. With a trip to the plastics store and a little time, I was able to make something similar for under $10. Is it as much of a precision tool as the LensAlign claims to be? I can’t say, because I’ve never had my hands on one. But I strongly suspect it is – my clone is based on the principle that the plastic box you get for $2.80 from the plastics store is likely molded as precisely as the LensAlign, and you set it up to use using the same parallax principle as the LenAlign.

Here are some photos of the finished gizmo. I don’t have step by step pix, so you’ll have to figure things out from the instructions, but they are pretty simple despite my long-windedness, so that should be OK.

What you will need:

an approximately 2.25” x 2.25” x 3.25” plastic box from the plastic store, 1/8” acrylic scrap big enough to get a 1.25” x 6” piece out of, liquid acrylic cement or thin crazy glue, a ¼”-20 bolt. You also want some white artist’s tape or vinyl tape, and some double-sided scotch tape. Plus a micro point Sharpie, or you could use a scriber. For the measuring part, you will ideally need a pair of sliding calipers, though if you are a good measurer, you can get by with a try square and ruler. You can get calipers from Amazon or similar for under $10 shipped http://www.amazon.com/Do-Best-Imports-820437-Caliper/dp/B00176CXHY/ref=sr_1_2?ie=UTF8&s=hi&qid=1258252505&sr=1-2. The calipers let you do two things: (1) Repeat the exact distance when you measure in from the side and top; and (2) draw a line that’s parallel to the side. You also will need to download and print the focus target (psd) or (tiff) and the focus ruler (psd) or (tiff) or you can make up your own.

OK, now that you have all your materials, here we go:

Adjust and lock the calipers at just under 1.125.” Place one jaw of the calipers against one side of the box and draw a line with the Sharpie about ½” long centered 1.125” from the solid top/bottom of the box (the idea is that you are using the parallelism of the caliper jaws to draw a line that’s exactly parallel to the side of the box). Now, on the opposite side of the box do the same thing, being sure to measure from the same side of the box you originally measured from. Now do the same thing measuring down from the top side of the box (for our purposes, the top side is the solid side, not the open side). If you have done things right, you now have two crosses drawn on opposite sides of the box that are exactly opposite each other.  You could to the same thing just with a ruler, but the calipers are easy and you know you're accurate with them.

Now print the focus target at 100% onto glossy photo paper (it’s set up as a 720dpi file in Photoshop to match the native resolution of Epson printer drivers, I don’t know what happens to the sizing if you print on another brand). Punch or cut a hole in the middle of the target, put two strips of double sided tape on the back, and position it on the box so the cross-hairs you drew are exactly in the middle of the hole. Now on the other side, place a piece of white tape over the cross-hairs on the outside of the box (for a background for the cross-hairs).

OK, now you need to make and attach the focus ruler to the side. Take your scrap of plexi and cut a piece 5.5” x 1.25.” You need to have a scrap where one edge is a clean 90 degree cut made with the table saw when the scrap was cut, because that clean edge is going to attach to the side of the box so the ruler is at right angles to it. The way to cut plexi is to score it, it’s sort of like cutting glass. You can get a special scoring tool at the plastic store for a couple bucks, or you can use a linoleum knife, or any sturdy knife for that matter. Put your straight edge along the plexi (I use a try square myself) and score along the edge until you have a nice score, then just break the piece off. Then score across that piece and snap off the end to get the right length. Print out the rule graphic, but don’t do anything with it yet.

With a pencil or ball point pen, mark the centerpoint on the plastic rule piece you just cut. With the box lying on its side, put the saw-cut edge of the rule on the box with the rule’s center point at the edge of the box, and the top side of the rule where it crosses the edge of the box centered on the middle of the cross of the focus target. The rule should be angled up at 20 degrees or so. Holding the rule in place, drop a little acrylic cement or crazy glue where the box and rule meet; capillary action will draw the cement into the crack and cement the pieces together. You only need a tiny bit. You may want to repeat from the other end of the joint. When it’s nicely set, cut out the rule you printed, put two strips of double sided tape on the back, and tape it to the top of the rule, so the zero mark is right at the edge of the box (i.e. the target plane).

Last thing to do it take the lid of the box (which actually is the bottom the way we’ve set things up), and drill or ream a ¼” hole on it so you can mount the box on a light stand or tripod to do your focus tests with a 1/4-20 bolt (you would use a 3/8 hole and bolt if that's what your stands have).

That’s it, you’re done.

To set up for testing:

You want to place the camera in front of the target using the formula (for 4/3 format cameras) of 1” of distance for each centimeter of focal length. Then, go into live view mode and center on the target, and then go into magnified view.

You should see the cross hairs, but not superimposed.  Move the camera left or right and the tripod center post up or down until the crosshairs align.  Then pan and tilt the camera to re-center the target.

Now you're ready to start the focus testing.  I'll have another tutorial for that in a while.

Feel free to repost, link to, etc. this tutorial, and have fun!