Exposure locks when pressing shutter release halfway in evaluative metering mode

Started Jan 5, 2009 | Discussions thread
Doug Pardee
Doug Pardee Veteran Member • Posts: 8,890
Re: Exposure locks when pressing shutter release halfway in evaluative metering mode

When using Evaluative metering, exposure needs to be locked whenever autofocus is locked. That's because Evaluative metering considers the image at the locked AF point(s) to be the subject, and recomposing between AF and metering would give the wrong impression of what is the subject.

If you are using a non-locking AF mode (AI Servo, for example) the exposure will not lock. If you're using AI Focus AF, exposure will lock initially but will unlock if the camera switches to servo AF.

This behavior is alluded to on page 168 of the XTi/400D manual:

"AE Lock: Auto: Applied in One-Shot AF mode with evaluative metering when focus is achieved…"

 Doug Pardee's gear list:Doug Pardee's gear list
Canon EOS 350D Fujifilm X-T10 Canon EF-S 17-85mm f/4-5.6 IS USM Fujifilm XF 18-55mm F2.8-4 R LM OIS Fujifilm XF 27mm F2.8 +13 more
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow