What exactly is the difference between access concentration and the first samatha jhana?

Have a look at this blog post, it's a piece I wrong on access concentration which may be of use to you.

As for the difference between the two, 1st jhana feels completely different to access concentration although access concentration has some aspects to it which can be used to get into 1st jhana properly e.g. shifting the focus from the breath to the pleasant sensations on the skin and taking that as your object. The main difference would be that 1st jhana suppresses the first five hindrances while access concentration does not.

I am new to this even though I've been working on concentration meditation, but I'll say what I understand at this point.
Please correct me if I am off base on my understanding because I feel like I am still working on the 1st jhana.

For myself I feel as if I have "access concentration" when I have my attention on the breath but without any effort.
Up to that point I have to continually bring my attention back to the breath because other things (thoughts, sounds, sensations) are still "sticky". That is my attention is easily taken away by them.

Also, a recent discovery is that when I am in access concentration I am not in any sort of "trance" or sleepy or anything like that.

In fact, my awareness or state feels just like it does when I am not meditating except it has a very nice focus to it. In other words I still hear sounds, feel sensations and stuff like that but there is so much more clarity to it because it is focused.
And the tiresome distractions that my mind is normally dragged through are gone.
It appears to me that the "pleasant" sensation on my body and moving my attention to it helps with staying focused on the breath.

After saying all that I can't say how it is different from 1st jhana because I'm not sure that I've ever gotten into 1st jhana.

-Gerry

To give a typical answer… “It depends.” Everyone seems to experience access concentration and any of the jhanas somewhat of a unique way, but there are some deep features.

When one begins to relax in a receptive way during sit, the mind starts to unwind and generate a bunch of words and images, and it doesn’t feel like it’s happening on purpose. If you continue to relax and allow yourself just to pay attention to what’s happening, at some point the lines of thoughts and sequences of imagery more or less drop away, and there’s a kind of felt-shift that takes place. It doesn’t have to be dramatic. The calm and collected state shows up is one way of conceiving of access concentration.

From here, focusing on the qualities of the state (tingling, calm, lightness, etc.) can lead to their intensification. Sometimes this leads to another shift, which can feels for some people like moving into another space entirely. It’s like access concentration, but more stable and intense. That’s one way of describing the transition from access concentration to first jhana.

Some people recognize the signs of concentration (i.e. how they know what state they are in) in a visual way, and others more in the feelings in their physical body. Neither are better than the other, so whatever comes up naturally is often easier to work with.

Also, there’s no guarantee that one will move from access concentration to first jhana in sequence. One can end up in one of the insight stages instead, even when there’s no intention to do so. Lots of repeated practice is really the only way to start sorting out what’s what.

-Jackson

Thank you for the responses. I have spent many hours reading up on this since first posting this naively simple question, and the controversy surrounding this topic, or more specifically the question of what is necessary and/or best to make progress, seems to stretch out to the horizon in all directions without end. I think it boils down to different strokes for different folks, and I am still getting my bearings.