the pronunciation of "-est" ending

[Xixi Luo]

By listening to the pronunciation by native speakers, I think "deepest" sounds like /diːpəst/ while "tallest" sounds like /tɔːlɪst/.
I have checked the dictionary, Webster dictionary shows "-est" ending has two pronunciations--/əst/ and /ɪst/.
If my judgements of the pronunciations of "deepest" and "tallest" are right, what's the rule? when to use /əst/ and /ɪst/?
Or only /ɪst/ is acceptable and I just got the pronunciation of "deepeset" wrong?

 

[emsr2d2]

I'm trying to think of an -est word in which I pronounce it as "est" instead of "ist" and I can't think of one. The majority of (I hesitate to say all but I'm very tempted) native BrE speakers pronounce it as "ist".

 

[5jj]

John Wells (Longman Pronunciation Dictionary) has the /ɪst/ pronunciation as more common than the /əst/ version.

 

[emsr2d2]

By After listening to the pronunciations by some native speakers, I think "deepest" sounds like /diːpəst/ while "tallest" sounds like /tɔːlɪst/.

I have checked the a dictionary; Webster Dictionary shows [that] the "-est" ending has two pronunciations - /əst/ and /ɪst/.

If my judgements of the pronunciations of "deepest" and "tallest" are right, what's the rule? When to do we use /əst/ and /ɪst/?

Or Is only /ɪst/ is acceptable? and Have I just got the pronunciation of "deepest" wrong?