If you are an artist, you know that it is a good idea to step back from your painting regularly to get a better view. There are lots of tools artists use to look at their painting to see if it is working. Some use a mirror - either a big mirror across the room or a tiny makeup mirror held at an angle from their brow. Others turn their painting upside down. Some use a camera and may change from color to black/white to check values.
I know that stepping back is the best way, but sometimes when I am concentrating on a passage, I just want a quick view to lead me in the right direction.
One neat little tool I use comes from my past quilting experience. Have you heard of a reducing glass? It is like a magnifying glass, but does the opposite - it makes the view look far away - just like you are looking at your painting from across the room! Jerry's has one that looks traditional, but it's pretty expensive:Jerry's- reducing-glass-lens And large!
But, I have a better version which is tiny. I keep one in my plein air gear and one in my studio. What I used in quilting design and now use for painting is a mini-reducing glass. Here is a link to one on Amazon: Dritz Design-Reducing-Tool and on Joann.com JoAnn design-reducing-glass These are easy to find at your local JoAnn Fabrics in the quilting department. If you are a JoAnn coupon subscriber you can use your 40% off coupon on this. I recently found a brand new one at a thrift store for a couple bucks.
Actually, I believe these are door peephole viewers! I always forget to look in the hardware department to see what these cost - but I am sure they are less than the quilter's version. The advantage to the quilter's version is that it has a bright blue plastic sleeve in the middle with a hole to attach a cord. I am sure this makes it easier to find the thing in your gear, or you could put it on a cord around your neck!