Light reflecting paint

White is as about as reflective as you can get, a mirror, or mirrors might help. Otherwise some artificial light?

The only paints I know that are sold as light reflecting work like traffic signs - they reflect back towards the light source, so you can see whatever has been painted better at night if lit by car lights or a torch.

I would paint everything in the hallway white and put large mirrors on the side walls at the window end.

Colin Bignell

yup

One trick is to change the direction of the incoming light from downward to upward. That way it hits a white ceiling rather than a darker floor. You can do this and add more light with a nearly horizontal mirror. Little 6" deep ones can be made to look ok. If it goes on the outside it adds more incoming light, if it goes inside it changes the direction of some already incoming light, so brightens the place less.

A fake window is also fairly easy to add, using fluorescents and a curtain.

Its also possible to add reflective paving outside, eg stainless steel.

And of course there is the bigger window option!

NT

More details needed. How big is the window? Is the window wall brick or stone? The ingoes of windows in stone walls can be lined with mirrors to dramatic effect. Large mirrors and very light paint and light-coloured floor covering make an enormous difference too.