Optimal aperture position?

Started 2 months ago | Discussions thread
aidaho Regular Member • Posts: 149
Re: Optimal in what sense?

E Dinkla wrote:

Well for most triplet and triplet related designs they decided to go for the second air gap and the aperture can be quite far to the rear in some

I've googled a triplet ray trace, and it's a bad news for aperture placement. It's definitely an afterthought and it's effectiveness won't match something like double gauss, specifically designed around one.

The second air gap is a bit more preferable since the aperture mech can be a bit smaller.

The point is whether the addition of the focal reducer can alter the optimal position of the aperture for the total. And I doubt it will bring it forward in the triplet designs.

This is an easy answer for aperture-designed lens: no. See my post above: aperture is placed where conditions were created for it by lens optical design. For a double gauss that would be an air-gapped concave surfaces. Since those ain't going anywhere whether focal reducer is present or not, aperture shouldn't go anywhere else either.

With triplets, I suppose there could be a small theoretical possibility of better aperture placement inside reducer itself, but just by looking into the FC patent, it's pretty obvious this won't be a viable option https://patents.google.com/patent/US5499069

So it's a "no".

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I like to shoot with manual lenses. Here are some of my photos: https://www.flickr.com/photos/curry-hexagon/

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