v.process (a film or photographic plate) less than the required time or in an ineffective solution or at an insufficiently high temperature
"These photos are underdeveloped"
英汉双解大词典
underdevelop/ˌʌndədɪˈvɛləp/
1.
V（动词）
to process (a film, plate, or paper) in developer for less than the required time, or at too low a temperature, or in an exhausted solution (胶卷、底版等)冲洗不足 [photog]