When you sit for a wet-plate collodion portrait, you have to be still, and you have to be still for a while. The lights are hot. The chemicals in the darkroom are toxic. And the prints are one of a kind; you, from a few minutes ago, appear on glass. This new show features five contemporary artists using the 19th-century technique: Ellen Susan depicts active-duty members of the US Army, referencing Civil War imagery made the same way; Joni Sternbach captures surfers, and Robb Kendrick real-life Western cowboys; Jenny Sampson sets up her darkroom at a skate park; and Seattle’s Daniel Carillo pictures the city via its artists. (Photographic Center Northwest, 900 12th Ave, www.pcnw.org, noon–8 pm, free)