DSLR Shots and Discussions

alcheng

In fact it's those cheap/less expensive lenses on the market nowadays.

They use polycarbonate instead of glass.

While glass provide better optical quality and will not turn yellowish, it is more costly.

Thus manufactures use polycarbonate thus to cut cost and weight. However, polycarbonate and plastic material lenses will turn yellowish from UV, thus the lens needs UV filter.

Well, if the lenses you are using are have glass lenses elements, then you are pretty much safe.