Luminosity in a painting is a difficult phenomenon to achieve. In fact, it is quite tricky to describe. What is meant by the term ‘luminosity” ? It will probably mean very different things to different types of artist - always an answer shaped by their own experiences. Looking at abstract art and comparing it with landscape painting an interesting point emerges; in a landscape, there is the ‘local’ colour of the scene -  the time of day will condition the type of light present. Add to that the geography of the place and you have a potent cocktail of light to respond to. Aping the effects or suggesting this light is quite a prized ambition of many painters and celebrated by the viewer - often tritely so. I have noticed this light alluded to in a lot of abstract art. This light has a single point of reference - sunlight from one particular spot, or angle in the landscape painting.
Amateurs love 'nature at sunset' as the saying goes. And this comment  holds water to quite a surprising extent, for it affords the opportunity to depict that warm glow and pick out all those seductive reflections and generally bounce the light throughout the painting. (You can learn so much by looking at amateur art - it is less egocentric for one thing and often has a nakedness that can be endearing, yet it provides a stern rap across the knuckles too of the pitfalls of lazy ambition in how paint is handled and what questions are not asked rather than the opposite.
Note though - the point of interest continued - that abstract artists often aim for the same sense of light - of ‘luminosity’, but in a different way - sans-motif - so to speak but with something more covert perhaps. Paint means colour, colour releases light. Effects of light are created by subtle references to local colour presented within the guise of a synthesis but missing the core of that synthesis (they lack the heat needed to metamorphose into a true abstract language.) Luminosity is inferred in lots of abstract painting rather than created. A received sort of 'heroic' brush-stroke often kicks up an area of the painting and this resultant graininess can lead itself to a suggestion of atmosphere  - it’s a sort of ‘pop-video’ aesthetic. In fact the more you think about it , the T.V. screen is highly pervasive in our sense of luminosity. It wasn’t invented when the Impressionists, Post--Impressionists, Fauves, were creating their glowing surfaces. In fact right up as far as early Abstract Expressionism it was still not a part of everyday life (or in colour) - certainly nothing approaching the screen culture we find ourselves in today.
Look at artists classified as “colourists’ post colour TV age and see how few - if any -  construct a luminosity through colour relationship as opposed to merely infer it in a ‘landscapey’ sort of way. Taken to its extreme light went on to become subject matter for the Neon artists. Quite ravishing effects of light can be seen also on the cheesiest of tv programmes’ studio sets. Painters should not try to compete with this - for a start it is generated light rather than reflected light. Yet compete they do and the world of sunsets appears once again - usually a feel of the exotic and definitely a beachy vibe helps. It’s a sort of “holiday abstraction”.
Morris Louis (an early hero of mine) is an interesting painter to mention here. He produced those large suites of Veil paintings with this sense of localised colour breathing huskily through their surfaces. Moving on to the more radical ‘Unfurleds” (they never fail to make me smile - in a gallery or even in a book)  - which are so optimistic they make your heart bleed and the colour is becoming structural. Yet when the last “Stripe’ paintings are arrived at a marvellous abstract language has fully blossomed. Luminosity has moved onwards and upwards. Here is a painter who is competing with Matisse’s sense of luminosity - but on his own terms - unlike say Jack Bush who did it more on Matisse’s terms. The paintings of the late 40’s (unsurpassed by any painter of any age in my opinion) through to the cut-outs are astounding examples of how to construct through colour. Compare these with Noland’s paintings - as radical and impressive as they are , there are still have vestiges of landscape - an inferred luminosity about them (strangely reminiscent of Vermeer at times, but with a sense of a ‘computersied’ camera obscura weighting in the works). In fact I once heard him say how close he considered abstract art was to landscape art.
A final thought. An ambition of mine has long been to produce a painting that you would find at the end of a trek through the jungle, not as a reference to your journey, rather as a prize to reach at the end of the ordeal. Painting is frontal - luminosity should also be frontal. It should be reached as a conclusion of the colour interactions across the whole surface not as an inference in one part of the picture. The trouble is, knowing it is one thing, producing it is not so easy. Whenever though, was a jungle trek supposed to be as carefree as a stroll on a beach.