Lens hoods do two jobs a lens cannot do for itself: blocking stray light from the side that would otherwise wash out contrast and cause flare, and giving the front element a first line of physical protection against bumps and rain. A hood left off is the most common reason an otherwise good photo looks hazy or low-contrast.
Hoods are lens-specific - the shape and mount must match the exact lens and its focal length, since a hood built for the wrong lens either does nothing or vignettes the corners of the image. Petal-shaped hoods suit wide lenses; cylindrical hoods suit telephoto lenses. Reversible designs that store hood-first on the lens for transport are worth prioritizing for field and travel kits. COLAMCO supplies lens hoods and camera protection accessories for the lenses business, government, and education programs already own.