Often he included himself in the scenes, eyes closed because of the long exposure time his process required.

他经常把自己包括在场景中，闭着眼睛，因为需要长时间的曝光。

The simplest explanation is exposure time.

最简单的解释是曝光时间。

The crude technique required educated guesses on exposure times, and involved heavy, awkward equipment — several men had to assist in its transportation.

这种粗糙的技术需要对暴露时间进行有根据的猜测，并且涉及沉重而笨拙的设备——几个人不得不协助运输。

At low radiation doses, the long exposure times caused a lot of intestinal problems for the mice.

在低辐射剂量下，长时间的照射会给老鼠带来很多肠道问题。

But exposure times were much quicker by the 1880s, and the introduction of the Box Brownie and other portable cameras meant that, though slow by today's digital standards, the exposure was almost instantaneous.

但到了 19 世纪 80 年代，曝光时间已经快得多了，盒子布朗尼和其他便携式相机的问世意味着，尽管以今天的数字标准来看很慢，但曝光几乎是瞬时完成的。