filter size

what does the size of the filter ring 50mm,67mm 77mm have on the picture if any?if the apature controls the light why have such a large glass?

thanks

mr.cj said:

what does the size of the filter ring 50mm,67mm 77mm have on the picture if any?

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None, other than possible vignetting.

mr.cj said:

if the apature controls the light why have such a large glass?

thanks

Click to expand...

In order to be able to open the aperture up, the glass needs to be at least that large.

Same reason why you have large diameter front element in a lense. That is the size of filter screw provided in front of the lense, and is proportionate to the diameter of the lense front element. Using a mall filter will interfere with light entering the lense front. It will vignette the edges.

Just look at the back side of the lens cap. It indicates what size filter is required. Using a smaller filter, the edge of the filter will be in the frame. Why diff sizes. It's just how the lens is made.