At last - Complete article on new way to use AF on the E-M5

Started Aug 28, 2012 | Discussions thread
Timur Born
Timur Born Veteran Member • Posts: 4,768
Re: Thank you. But what are your tips?

Pixnat2 wrote:

  • instead of pressing the shutter all the way directly, it's more efficient to press it halfway, get the focus OK, then press the shutter all the way.

Apart from using AF-S and fully depressing the shutter all the way right after turning on the camera (which doesn't work due to a bug) I did not experience significant differences between half-press first and full-press at once, with one exception: It is always beneficial to pre-focus close to the focal plane that you want to focus on when taking a shot. Once you've done that it is much safer to just fully depress the shutter.

  • use the zoom AF to get more focus accuracy

Zoom AF is not necessarily more accurate in all situations. I had targets where Zoom AF would focus while normal AF-S would not, but I also found at least one target where Zoom AF would not focus while normal AF-S did.

For the time being the most accurate focusing method for static frames (target + surrounding + camera shake) may be AF-C. It's the most complex focusing method of the E-M5.

The main problem with AF-C is that there is lens back and forth hunting after the camera signaled "in focus". You have to watch closely to notice. Only after keeping the frame mostly - but not completely - motionless for several seconds will the hunting stop.

Here is how it works in detail once you start half-pressing the shutter button, in order of occurence.

1) Quick initial AF-S type focusing, including automatic change of screen exposure if necessary and increase of contrast during the AF-S focus phase (same as AF-S does). Green focus light blinks during this phase.

2) Audio beep.

3) Switching back screen-exposure to what Live View would show without touching the shutter button.

5) Green focus light turns solid. (Considerably later than audio beep!)

6) Hunting slightly back and forth while the shutter is kept half-pressed. Green focus light stays solid and "Shutter Release Priority" OFF allows to take out of focus shots.

7) When the whole frame is kept mostly motionless for 2 to 3 seconds the hunting will stop and the image will be in focus. Green focus light stays solid.

8) Once enough motion is detected, either by camera shake or subject motion, the green focus light starts blinking again. You may hear a second beep at this time.

9) Back to step 5.

AF-S usually uses a difference screen exposure and contrast than Zoom AF (even when you try to match the screen content/framing), but both may increase or decrease exposure and contrast during focusing. The hunting phase of AF-C does not change screen exposure and contrast, but stays to the same settings/view that is used by LV when no focusing happens (no shutter half-press).

These different behavior lead to different focusing results, especially in different light. I had a dark wall patch where AF-S could not focus, but Zoom AF could. And I had a woven basket in shadows where AF-S could focus, but Zoom AF could not.

Zoom AF ignores AF-C, by the way, so it can be used as a quick means to switch between AF-C and Zoom AF-S type focusing without having to enter any menus (just double tab the Magnify button).

 Timur Born's gear list:Timur Born's gear list
Panasonic Lumix DMC-LF1 Olympus OM-D E-M5 Nikon D750 Nikon AF-S Nikkor 50mm f/1.4G Olympus M.Zuiko Digital 45mm F1.8 +3 more
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