For spotting I have always found a slight magnification certainly helps in very light areas and very dark areas, enabling one to very carefully place the tip of the spotting brush exactly where you need to place it.
Using just plain eyesight is reasonably good, but even if you have really good eyesight, with or without spectacles, a magnifier certainly helps you nail that placement of the spotting brush.
I have found that a magnification of between 4x to about 6x magnification works well for me. Mostly I use a garage sale bought hand magnifier which I think is around 4x magnification.
Essentially, you just need to be able to use the magnifying glass enough distance away from the paper to allow side light to still fall onto the print. If you need to hold the glass closer you probably need to get another strength magnifier that allows you to hold it slightly further away.
I just checked with my current magnifying glass and the glass is about 120mm away from the paper when I have it in focus. This gives me easy access to the paper, yet allows me to precisely place the brush.
Something like this is similar to what I have:
https://www.craftlamps.co.uk/product/handheld-magnifier
I use Winsor and Newton brushes. My standard brush is a Series 7, 000 brush. For really fine work I use a Series 29, 00000 Spotting Sable brush. Yes, that is five zeroes.
To use the 00000 brush successfully I really believe you need magnification to see exactly where you are placing the super fine brush tip.
Spotting is easy, doing it well is a little difficult, but easily doable once you get used to the technique of spotting. Spotting can be done so well that it is invisible, it is not hard to get to that standard.
Mick.
