Final answer:
During the 1860s, exposure times for daguerreotype portrait photography typically required between 10 and 15 minutes.
Step-by-step explanation:
In the 1860s, portrait photography was still dealing with the challenges of long exposure times. The daguerreotype process, developed by Louis Daguerre after working with Joseph Nicephore Niepce, required between 10 and 15 minutes of exposure. This is evident in the image of the Parisian Boulevard du Temple from 1838, where only stationary objects and a man getting his shoes shined were captured due to the long exposure time required.
Advancements in photography sought to address various challenges including speed, resolution, and permanence. However, until the 1870s, exposure times did not see significant reductions. Eadweard Maybridge's photographs in 1878, which captured a galloping horse with an exposure time of 1/25th of a second, celebrated the progress made in reducing exposure times.