Long and short vowel sounds

[eeky]

Amongst native speakers, is it always clear from the sound alone whether a short or long vowel has been said, or in less careful speech do people put out vowel sounds that are phonetically ambiguous, so that one needs to figure out which is meant from context?

 

[Glenn]

After having heard some of 若本規夫's work, I'd say context plays a role in some people's speech. But it's harder for me to understand, at least. Not sure how much of a difference it makes for native Japanese speakers.