As 140 characters is not enough to convey the message. When an image added to the tweet, the character limit is reduced to 117 characters. How could we able to convey the message? Any reason why the character limit reduced?
The character limit is reduced as for the Image a link is placed in the Tweet. This link length counts against the 140 character limit, as far as I know. I don’t think there is a way to circumvent this limit.