Visual Arts:Marc Reilly's paintings in 16 Eustace Street veer in scale between tiny, large and very large. There's nothing in the mid-range, the preserve of conventional easel painting, and that's appropriate, because there is something extreme and uncompromising, all-or-nothing, about Reilly's approach to art.

The exhibition title refers to the address of his studio in Dublin. The work itself, though, as in the past, refers to elsewhere, mostly to a regular stomping (or walking) ground in Co Wicklow. He has made watercolours on the spot in Wicklow but this time the work was made in Eustace Street.

He often refers to specific dates, times, places and weather conditions in relation to individual pieces. Given all this it's hard not to think of the nature romanticism of Wordsworth, of the spontaneous expression of "emotions recollected in tranquillity". Reilly's paintings certainly are recollections of intensely felt experiences. It's not that the experiences are momentous or epiphanic in themselves, in fact they are usually quite ordinary. It's more to do with the level of sustained attention, the meditative consideration, with which Reilly invests them.

Having said which, the paintings in 16 Eustace Street allow more than the recollection of emotion. They allow the pure signal of recollection to be distorted by local interference, so to speak, accommodating the static and noise of the studio. Mind you, this happens to a greater or lesser extent. One hauntingly beautiful painting, Lydia's garden, late, a busy colour-field composition in which silver and a purply blue vie with each other for supremacy, is essentially pure in the sense that it is minimal and focused entirely on its nominal subject.

Upriver, lateon the other hand, features wide, looping lines that surely indicate the intrusion of the present moment on the past. It and several comparable pieces, including the nicely titled Ghost, are exceptional and really well judged.

And that's not to mention the tiny pieces, which are also fine works in a way quite different from their much larger companions. Reilly is like the painter Cy Twombly in at least one regard: much of what he does seems to arise out of the impossibility of making particular kinds of paintings anymore. Out of his awareness of that impossibility, something new emerges.

One reasonable way of describing Sinéad Ní Mhaonaigh's work at Kevin Kavanagh is to say that she makes paintings of spaces and structures. Her show is called Platform, following on from her previous exhibitions, which mapped out spaces of possibility, often alluding to such performance venues as stage, playing field, racetrack or other kinds of stadium - or apparently so, since she did not actually specify.

Such imagery, it seems fair to surmise, can be read metaphorically. Her evocation of these spaces and structures was achieved by means of a vigorous, muscular style of painting, in which each picture was worked over and scraped back in fast, broad swathes.

Her distinctive palette included earthy browns, vegetative greens, rich pinks and off whites.

All of which is true of the paintings in Platform, though there are new developments. While there are a couple of fine examples of arena-like structures, there is also a move towards what looks like natural landscape, with references to mountains, valleys, lakes and skies. But that's not all. There is also an implied equivalence between the character of the landscape and the female body. This isn't done as schematically as it is in, say, Georgia O'Keeffe's flower and landscapes paintings, or Kathy Prendergast's Body Mapwatercolours, but it is certainly discernible.

Ní Mhaonaigh's spare formal language is partly necessitated by her bold, gestural style, which sweeps all before it, but it's also a matter of choice, and some of the simplest paintings, almost cartoon like in their imagery, are also the best. She is clearly capable of achieving lush painterly effects in terms of colour and texture, and does so, with succulent expanses of creamy white pigment, for example, but she is never facile or indulgent and there is a measured, critical edge to her work. So much so that one or two pieces in the show are positively stark.

One could ask why she refers to specific images but simultaneously keeps her distance from them. The answer is that indeterminacy is the point. Everything in the work circles around possibility, safe-guards a moment of potential. The field of our desire, the performative space, is unoccupied, but all the more attractive for that, charged with tension and opportunity. That is what gives the paintings their tremendous energy.

At the Cross Gallery, Ann Quinn's Autumn in Middle East, Summer in Westfeatures an unlikely conjunction of locations: travels in Iran and a residency in Glenveagh National Park in Donegal. Given the geographical distance and differences, the uniform look of the work is disconcerting, and even intriguing. Is there an equivalence between the two sites? Not really, but Quinn's carefully calibrated mode of representation wins out over the local differences.

That is, she is a representational painter within tightly defined parameters. She is greatly influenced by photography but her images are not photographic as such. She likes the smoothness and impassivity of the photographic surface, particularly when burnished and polished in the virtual reality of cyberspace, and on one level her paintings are as blandly even in tone as stylised computer games.

Yet, in a way that recalls Elizabeth Magill, she likes to muddy the representational waters.

She interrupts the smooth surfaces with various blemishes and interruptions that, once we've become conscious of them, undercut the illusion our eyes so readily accept. With similar effect, what at first glance comes across as a photographically true account of clouds turns out, on closer inspection, to be nothing like a cloud at all, and much more like abstract mark-making. Her paintings depend on this flickering between seamless pictorial illusionism and sly reminders that we are looking at hand-made contrivances.

They work because she has a distinctive visual sensibility. A couple of the Iranian landscapes are tremendously atmospheric renderings of cities viewed from distant heights at dusk. Though small, the paintings have a real sense of scale and distance.

Elsewhere, everything is deliberately foreshortened. As though we are stalking deer in Glenveagh and are pressed into the earth, we see just a fringe of bracken and, above, a vast expanse of sky. A mood of still quietness pervades virtually all of her pictures.

• 16 Eustace Street, new paintings by Marc Reilly, the Paul Kane Gallery, 6 Merrion Square, ends Jan 26;Platform , paintings by Sinéad Ní Mhaonaigh, Kevin Kavanagh, 66 Great Strand Street, until Feb 2;Autumn in Middle East, Summer in West , paintings by Ann Quinn, Cross Gallery, 59 Francis Street, until Feb 2