Shadowy Daisy

Shadowy Daisy
by damned-truths

Submit your Photo
Hall of Fame

Please participate in Meta
and help us grow.

Photography Stack Exchange is a question and answer site for professional, enthusiast and amateur photographers. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I stumbled across the Sony 135 F2.8 [T4.5] STF other day.
I have read through the review but I can't for the life of me figure out what the twin-aperture setup is supposed to do!

share|improve this question
up vote 1 down vote accepted

Basically there is a manual iris that is designed to produce as round an opening as possible in order to render out of focus highlights as circles (instead of pentagons, octagons, etc.)

Since the whole purpose of this lens is to produce smoother blurred backgrounds using the apodization element, it would be a waste if the effect were ruined by not having a circular aperture when stopping down slightly.

Presumably having this aperture stop right down would compromise its roundness, so they added a second aperture which can close all the way down for when you want a very narrow aperture.

share|improve this answer

From the article:

This lens has two apertures; the stepless aperture, manually controlled with the aperture ring, and the automatic aperture (A position), controlled by the camera. In the stepless aperture setting, emphasis is put on the aperture shape, which is rounder than the automatic aperture. For large aperture settings, selecting the stepless aperture is recommended.

share|improve this answer
See also – JDługosz Jul 2 '15 at 22:11

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.