XF 56mm ???

Started Mar 18, 2014 | Discussions thread
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Re: XF 56mm ???
In reply to Mikess1, Mar 18, 2014

You've gotten some helpful advice so far. We don't really know where you're coming from, so it's hard to be very specific. If you haven't shot mirrorless cameras using contrast-detect AF (CDAF) before, and/or if you haven't shot a 56/1.2 or similarly fast lens before, you should expect a low hit rate, especially with busy backgrounds and non-ideal camera settings. DOF at 1.2 is very thin, and you may not understand what the camera needs to see to properly lock-in focus.

The CDAF sensors are looking for contrast differences, fixing the focus point when what it sees INSIDE THE BOX is at peak contrast. It doesn't measure distance per se, so if the contrast is stronger on the base behind the sink spout, that's what gets focused. Camera found the max contrast, locked focus, and did the correct job as far as it can tell. When the hands in front of the couch make up only 30% of the box area, the camera is likely to maximize contrast somewhere else.

As light levels get lower, the camera has a harder time. Often our eyes see contrast differences in dimmer light that the camera can't.

So you do need to make the focus box as small as possible, you have to watch your backgrounds, and you have to think about where you place the box. You should expect some bad focus lock with similar/busy backgrounds (faucet shot) or with the box too big (hands in front of sofa).

Box placement and focus/recomposing is sometimes necessary. If you moved the box down/right in the hands/couch shot, so the hands filled most of the box, the camera probably would have focused on the hands.

You may find it quicker and easier to manually focus in situations where the camera is having trouble.

If you're coming from a DSLR, they use Phase Detect AF (PDAF), an entirely different beast. PDAF can sometimes lock focus in dim light a little better, but not in live view or video. PDAF has other shortcomings that CDAF does not.

Your XT1 uses both CDAF and PDAF, but the PDAF focus sensors are only (primarily?) used when shooting action in AFC/burst mode.

Mikess1 wrote:

Activatedfx wrote:

...The faucet spout "blends in" with the handles behind it - it almost looks like it's on the same exact plane, and it doesn't stand out as the "thing to focus on". There's simply no detail or contrast for the lens to lock onto!... Same problem with the other photo in your 1st post.

I was also having some minor issues focusing on very small, specific items in front of busy backgrounds with the 56, and I found that making the green box smaller really helps. At f/1.2, it is a very exotic lens, and it needs to be used correctly. Practice will help as well!

you are probably right just tried a couple pictures of my daughter and i cannot get it to miss focus at all

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