I know using the bare infinitive after verbs such as hear, see, watch, etc. conveys a different meaning from using the present participle (verb+ing):
- I watched him climbing over the fence ( Climbing wasn't finished at the moment of speaking)
- I watched him climb over the fence ( Climbing was finished at the moment of speaking)
I noticed the majority of the Grammar books use past tense to explain the aforementioned difference. Personally, I think that is quite rational because the bare infinitive implies a completed or finished occurrence. This means that event belongs to the past. However, I have a problem conceiving similar sentences in the present tense. For example:
The questions is:
If the bare infinitive implies a completed action, then why should we use the present tense to talk about that event? (the event is in the past).
We can say that:
An uneasy feeling came over me as I watched him walk towards the revolving doors
Added info 1
If you think my "climbing" examples are irrelevant, you can check Cambridge Advanced Grammar In Use, page 60, Unit 30, Section D or just check this link
Added info 2
My question is from the logical point of view. I think the act of "seeing" is instantly. Therefore, it is not rational to say "see" a "completed process" but, "saw" a "completed process".