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Lifespan of a Nikon lens...
- Thread starter jacotte
- Start date
At equal settings (2.8) the prime lets in more light than the zoom. Does that mean the zoom is getting old? If so, what
No, it just means there's a lot more glass elements on the zoom lens that light has to pass through.
Obviously. However a 2.8 is a 2.8. It should be the same amount of light for both or else what would 2.8 stand for if you could not expect the same amount of light.
F-stop do not take into account light transmission, only the focal length to iris diameter ratio (so it assumes that the lens absorbs no light or there's a 100% transmission). That's why T-stops are used, where each lens is individually tested at the factory for how much light is transmitted and assigned a T-stop rating; two lenses rated at the same T-stops lets in the same amount of light, 2 rated at the same f-stop might or might not. Now for the newest lenses f-stops are pretty much identical to T-stops, but older lenses might not follow this convention.
Are you telling me that a prime set at 5.6 could actually yield more light than a zoom set at 3.4?
Like I said, there are variations across lenses depending on how many elements there are, what coating were used, etc. F3.4 to f5.6 is about 1.5 stops so I don't know if the difference would be that extreme. But there's no "rule" per se. You need to test out each individual lense and see how they perform.
So how do you know if a lens is reaching its expiration?
when the aperture blades stick, when the focus ring seizes, when its no longer of use. most old lenses that are cared for will last forever.
Some old lenses that use thorium in their glass turns yellow over the years which results in a yellowish hue and less light transmission in the image. But blasting it with UV light will bleach the glass back to normal.