My problem is that I had 20/20 vision all along until, some time in my 40s, I started needing reading glasses in low light and, over the years, things kept going. My longer range vision is holding out fairly well, and in fact to wear corrective lenses has absolutely never been a consideration so when I'm out and about I don't even think of bringing reading glasses...sometimes to my detriment
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When shooting, the diopter fortunately works for me, but there are times it sure would help if I had remembered to bring along reading glasses when the light is low and I need to check something! At some point the illumination button comes into play...but I still sometimes kick myself...and, manualy focusing using Live View I really need them around!