DPReview.com is closing April 10th - Find out more

2x zoom lens with same absolute aperture instead of extender ?

Started Aug 16, 2015 | Questions thread
Steve Balcombe Forum Pro • Posts: 15,582
Re: 2x zoom lens with same absolute aperture instead of extender ?

Michael Fryd wrote:

Steve Balcombe wrote:

...

Yes, but as per my earlier post the front element of a long lens is the size of the entrance pupil. The shorter the lens, the less true this is.

...

The aperture is the weakest link in the chain. Typically, that will be the size of the front element, but that's an engineering decision, not a requirement of physics.

I'll say one more time - *not* with a long lens.

When the most oblique rays are arriving from angles of less than two or three degrees from parallel with the lens axis, making the front element significantly bigger would just result in collecting light which could never reach the sensor. It *is* physics which determines this.

Post (hide subjects) Posted by
irm
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow