slight shadowing in view finder

if i focus on a bright light, or desk lamp ... there seems to be a faint shadow of that bright item. In taking the shot, it does NOT appear in the actual photo.
Only seems noticeable on very bright photos such as side onto a light bulb etc. does anyone understand what i mean, know what this is? happens across different lenses.
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Only seems noticeable on very bright photos such as side onto a light bulb etc. does anyone understand what i mean, know what this is? happens across different lenses.
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