It is virtually impossible to see the tiny little stitches in your embroidery without the help of a magnifying light, it reduces eyestrain and I highly recommend you use one, it will be the best investment you ever made!
Most of the errors I come across in Needlepainting are due to not using a magnifying light. There will be little gaps in the stitching which spoils the flow of the work and these cannot be seen without the aid of bright light.
Which light to buy
There are many lights on the market, you could begin by looking online at places like Amazon or any craft/needlework stores. I currently have a Daylight Omega 7 LED light with 15cm lens, but also use a slimline LED magnifying lamp from the Daylight company. It has a 13cm (5 in) lens with 1.75 magnification as shown top left. You could also get something more portable like the one bottom left. Here are some pointers when buying a light.
Daylight & LED
It should have daylight or white light not yellow light from a light bulb, so it does not distort the colours in your project. LED lights are best - but the light should have at least 21 LED bulbs. Any less will not give the required light.
Light versus magnification
Light is more important than magnification. Magnifying an area without good light is useless it will just make a dark area bigger. So first and foremost look for bright white light.
Magnification & Size
It should have magnification of at least 1.5. The light face should be large enough for you to see through comfortably. You should be able to sit comfortably in your chair whilst stitching and the light should reach you - you should not have to bend towards the light.