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A project log for Affordable Reflectance Transformation Imaging Dome

A simple and inexpensive way to image and analyze subtle surface details on objects.

Leszek PawlowiczLeszek Pawlowicz 06/05/2016 at 20:200 Comments

Hopefully, after reading the previous log, you have enough info to figure out how big a dome you need. But there are a few more details you may need when ordering a dome.

- While you can use any dome-shaped object you like, like a styrofoam dome, I've always used acrylic domes. They're sturdy, and come in a wide range of sizes. My source for domes in the US has been EZ Tops Worldwide; they have a wide variety of sizes and styles, and prices are reasonable compared to other sources I've seen online. Outside of North America, you're best off finding a local supplier if at all possible; shipping costs for domes are high. If you're from outside North America, and find a good dome supplier, please let me know in the comments and I'll add them to a list.

- Speaking of which: the prices at EZ Tops are for the domes alone. Shipping costs can easily increase the cost by a factor of 2 or more - the larger the dome, the higher the factor. I'm guessing this will be true for any acrylic dome vendor.

- When spec'ing the dome, make sure to specify the following dimensions:

- EZ Tops domes come in several acrylic colors: clear, white, tinted, and black. You're going to be painting the interior of the dome to minimize intrusive lights, and light scatter, so any of these would be usable. Clear is the cheapest option, and will have a cool shiny black appearance after you paint the inside of the dome; this is best for any domes you will only be using indoors. For a dome intended for outdoor portable use, I'd recommend white, since that color will help keep it cooler in the sun. I'd stay away from tinted or black; not only are they more expensive, but they make marking the positions to mount LEDs more difficult (you'll see why in the first instructions section, coming soon).

- Domes need to have a hole in the top for the camera to look through. I have manually cut holes in acrylic domes several times for this purpose, but I will never do it again. Acrylic is very tough to drill through - melts when you cut, the bits catch on the edges, and it cracks/breaks all too easily. When you choose a dome supplier, make sure they offer the option to cut a hole in the top. Costs a few bucks, but it's definitely worth it in ease and peace of mind. The size of the hole will depend on the size of the camera lens/aperture you plan to use with the system. 2.5" is a good size for most point-and-shoots, and also for DSLR macro lenses that won't need to be lowered into the dome (e.g. for a 12" diameter dome, 6" hole to specimen distance, 6" lens working distance). If you do need to lower a macro lens into the dome a bit to get closer to the object, you'll need to specify a hole diameter that will allow the entire lens to fit inside. I think 3" should work for most macro lenses, but you'll need to check your lens size specs to make sure.

- Don't throw out the box they ship the dome in - it makes a handy carrying container.

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