The most obvious difference between first-person/subjective and limited-omniscient/limited-third narration is that the first is I and the third is he/she/they which creates immediate distance from the characters. We had another ‘character’ the narrator/authorial voice relaying the characters’ thoughts. As I’ve mentioned before this separate entity is used as a reason to refer to an omniscient narrator as a ‘reliable’ narrator because the narrator is separate from the story and therefore has no reason to lie.
It always seemed an odd concept to me as the narrator leads us through the story not always telling us everything. In the case of limited omniscient narration the narrator can’t tell us everything at once anyway because they’re limited to the perspective of the character they’re focusing on. However, this doesn’t mean they’re going to tell us something the character knows or jump into the head of another character who knows something that could give away that special twist they’re trying to hide. They might be telling us the truth, but they might not be telling us the whole truth with suggests an ‘unreliable’ narrator.
This brings us on to another difference between the two because a first-person narrator usually has only one perspective in the book, unlike a limited omniscient narrator where there can often be multiple narrators. Once again though this isn’t entirely true, it is possible to have first-person stories with multiple narrators. Sometimes this uses chapters from a limited omniscient narrator or an omniscient narrator spaced out within the story. Rarer occasions another technique is to have multiple first-person narrators, both Joanne Harris and Sarah Waters have used this technique. In Sarah Waters’ novel Fingersmith we seem the same events from the perspective of two different first-person narrators revealing a clever narrative twist. The issue here would be creating two distinct narrative voices for two distinct narrators.
We stumble a again in a definitive difference because while we can argue that the limited omniscient narrator is outside the characters and should have a voice of their own, and this is a perfectly valid method. We may choose to keep the narrative voice very close to the character’s voice which can be a useful way to draw the reader in to follow the character, a strong point of first-person narration.
My point being with these not-so-different differences is that in writing we can apply techniques from what may appear to be unrelated areas to mix-and-match to create the effect that we want in our particular style. Although we have different aspects with different labels this doesn’t mean that everything fits into neat little boxes. More than one writer has described writers as thieves stealing from all over the place; life experience, other writers, other writing techniques. This is another reason why I like to emphasise that there are different techniques and advice is advisory because of this flexibility.
Simply because we are working in one form of narration, or genre, or anything else doesn’t mean we can’t use elements of others.