Depending on the lens' focal length, the image will deform and affect how the image looks in photos.
根据镜头焦距的不同，图像会随之变形并且会影响最终的照片效果。
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Using a group of mirrors and a housing that's almost big enough to use as a coffin, Canon was able to stretch the focal-length on this SLR-specific lens to 5,150mm.
What excites ophthalmologists most, and what every lens-making company wants to achieve, is an “accommodating” lens that can change its focal length in the same way that a natural lens does.