In a post last spring, Olympusman wrote, "One trick I have taken up recently is to shine a flashlight through the camera eyepiece to create an axial spotlight to help ‘find’ and center the mounted insect initially."
I have also used a flashlight this way, but find that an inexpensive laser works much better—so much so that after almost three years of working with a sighting laser (as I call it), I wonder how I ever got along without one. Olympusman's remark reminded me that I've been meaning—far too long—to share. Below, I'll try to demonstrate why I find the sighting laser so useful, and give a parts list for others who want to make one.
A laser shining through the viewfinder of a DSLR shows precisely where the camera is aimed. Vitally, it also shows when the lens is in focus. Looking at the beam of the sighting laser on the subject, I can aim even a 100x objective and adjust it to within 50 microns of perfect focus. Only then do I bother looking through the lens, quickly tweaking focus on a computer in liveview. Those who work at higher magnifications will understand the utility of this. On traditional microscopes, one first performs positioning and focusing with a low-powered lens, then rotates the turret to sequentially higher and higher magnifications, tweaking position and focus with each step. It’s hard to go straight to high magnifications without this step-by-step approach—you won’t know what part of the subject is in view, and depth of field is so thin that finding focus requires a long, frustrating search.
But the sighting laser is not limited to high magnifications--I find it great convenience even down to 2x.
Here is a 50x objective in focus:
Same 50x objective, out of focus:
Focusing at 50x works like this:
In actual use, the focused laser beam is far more clear and crisp than it appears in these photos, and is shaped like a tiny cross hair. But the brightness of the laser beam, compared with the subject, greatly exceeds the camera’s contrast range, and I didn’t feel like doing HDR for this post—so the central portion of the beam is burned out.
With a lower-powered objective, the laser cross hairs are much larger. Here is the laser with a 2x objective, in focus:
Focusing at 2x works like this:
A homemade bracket holds the laser in correct alignment:
Here is what the sighting laser projects in plain air:
You can make your own sighting laser for very little money—about $20 USD. Perhaps a bit more if you don't already have a few simple tools and shop supplies on hand, or less if you can scrounge an item or two from your scrap box. A potential parts list is below. It differs slightly from what I've shown in this thread, due to changes in availability and the fact that, as I've experimented, I've mixed portions of different offerings. But it is very close to what I’m using.
A: Homemade bracket for DSLR eyepiece. The bracket shown here fits my Nikon D200 and D7100 bodies, and was surprisingly easy to make. The materials were pieces of aluminum right-angle stock and aluminum flat stock from my local hardware store. These cost only a few dollars, and since they are handy for a wide variety of jobs, I keep a selection on hand as shop supplies. If you don’t have them already, you should be able to get lengths of several useful sizes and shapes for under $10 USD total. Depending on what brand and model of DSLR you use, you may need a different shape—but regardless, it should be easy to make.
Aluminum, being a soft metal, is easy to work by hand. The only tools needed to make this bracket were a hacksaw, a file, and a drill.
For anyone daunted by even rudimentary metalworking, I'd urge you to go ahead and jump in at this level. While I take difficult work to my fabricator, this bracket did not require his expertise or equipment. A hacksaw (a hand saw for metal), is a roughly $10 USD item. For this project, I would strongly recommend purchasing a round "rod saw" blade for the hacksaw, such as this one ($5 USD). This thin, round type of blade allows you to cut in any direction—in this case, down, then sideways, then up. I’d suggest you cut a slightly smaller hole than is required by your viewfinder, then enlarge it—slowly, with a hand file—until you get a precise fit.
As an alternative to making one's own bracket, perhaps it would work to purchase an inexpensive “universal” right-angle viewfinder that includes adapters for assorted cameras, and alter one of these adapters to hold a sighting laser. I haven't tried this.
B: Laser module. (Includes laser diode, barrel, focusing mechanism, and cross-hair lens.)
"650nm 660nm Red 5mW Laser Cross Module Diode w/ driver": $6 USD
This eBay item—and the above image—came from eBay vendor buyamore. I’ve purchased a number of items from this vendor, and my experiences have been good. (Also, shipping is free.)
This laser requires 3 volts DC, and draws less than 45mA of current. (These numbers will become important when choosing a power supply.)
Regarding the laser’s output power: I chose a reasonably low-powered laser of 5mW (milliwatts), in the color red (650-660nm). These specifications are similar to office laser pointers. The U.S. FDA categorizes these as "Class IIIA" lasers, safe for "responsible use" by consumers, and unlikely to cause eye injury if brief mistakes occur. My 5mW lasers are bright enough for easy use with low-powered objectives in a well-lit room; as magnification increases, I often prefer to dim the room lights while sighting with the laser. Since my room lights are controlled by foot switches and turned off for shooting, this is convenient for me. Still, I’ve purchased, though not yet installed, a more powerful laser. I think it is safe in my implementation.
C: Mount/heatsink
"Mount/Cooling/Holder Heatsink 12.5mm Laser Diode Module Cool System Fixed Device": $5.50
Image from eBay vendor buyamore
The above item doesn’t seem to be as finely finished or anodized as mine, but should work just as well. The term “heatsink” is a misnomer here—we’re just using the item as a convenient mount—but “heatsink” is a useful search term.
D: Power supply for laser
Among many power-supply options, here is a nice one: Jameco AC to DC power supply wall adapter transformer single output 3.3 volt 1.5 amp 4.5 watt: $11. You can safely ignore the fact that this unit outputs 3.3 volts, rather than the laser’s nominal 3 volt rating.
Image from Jameco
This is a good place to note that the laser listed here includes a built-in “driver,” which simplifies hooking it to a power supply. With a built-in driver, you need only control the voltage delivered to your laser—the driver limits the current.
E: Switch
The way a switch feels in my hands influences the satisfaction I get when using it, so I purchased locally, flipping quite a few switches on and off before choosing. The switches I chose are not the cheapest available, but feel good in hand. I use both a momentary pushbutton switch and a toggle switch, wired in parallel. The pushbutton switch lets me flash the laser briefly; the toggle switch allows a hands-free “on” state. (If you pick just one, I recommend the toggle switch.)
Pushbutton switch—RadioShack part# 275-646: $3.50
Toggle switch—RadioShack part# 275-663: $5.50
Pushbutton switch (image from RadioShack)
Toggle switch (image from RadioShack)
F: Project box
Many small containers will hold the switches. I used a RadioShack part# 270-1801: ($3.50). This is a small project enclosure (aka "project box"). Since the Bratcam's base is made of steel, I attached magnets to the bottom of the project box to hold it in place.
Project box (image from RadioShack)
Details on laser lenses:
You can swap lenses, if you prefer a dot-shaped beam to a plus-sign shaped beam. For a few more dollars, one can also buy glass (rather than plastic) lenses. I’ve wondered if these improve performance, but have not tried them.
Image from eBay vendor buyamore
... gonna have a re-think ...
, and I think the cross hairs are a significant advantage.
...