SAF Front Focus and CAF/SAF Focus Comparisons with the 300mm f4 – E-M1s.

Started 3 months ago | Discussions thread
OP drj3 Forum Pro • Posts: 10,926
Re: SAF Front Focus and CAF/SAF Focus Comparisons with the 300mm f4 – E-M1s.

Gary from Seattle wrote:

drj3 wrote:

Interceptor121 wrote:

Something is going on with the programming of the functionality here. I doubt it is a hardware problem

I am convinced it is the CDAF algorithm. It has a slight bias for the closer area within the focus points. As long as the user is aware of this issue, it is easy to avoid the problem.

It would rarely be a problem when one uses a single or limited focus area. I almost always use SAF and a single focus point with my 12-100mm f4 lens unless I am photographing a moving target or a small target at minimum focus distance.

It can be a problem when you have a very shallow DOF with very long telephoto lenses when photographing close targets or a very fast lens of any focal length photographing close targets. It is typically a difference in focus around the chosen focus point since the focus point would generally be within the DOF.

I have thought about this with S-AF and CAF. I wonder though if the chosen array/single target pattern makes a difference with CAF+Tr? I am currently using a five target cross on CAF+TR. Would I do better if I used a single small target? I haven't been doing that as I am not sure that I can consistently be that accurate in targeting; or would it make no difference in CAF+Tr because the camera essentially takes over in matching bird shapes and eyes in AI?

With CAF the camera would typically be focusing on the most distinct feature in the target area with no real focus bias.  I doubt there would be much difference in the five cross and a single point with CAF+TR, since the camera will be trying to focus on specific target characteristics.  Once focused, the shallow DOF will generally result in your target being more distinct than background features.

Where it would make a difference is for situations where the background is essentially at the same distance as the target and just as detailed.

For example, I always use CAF with a single point for photographing hummingbirds and hummingbird moths eating from flowers with the flower petals, leaves and stems all very close to the bird/moth where the focus can quickly jump to the background.  One tenth of an inch is the difference between feather detail and a deleted image.

-- hide signature --

drj3

 drj3's gear list:drj3's gear list
Olympus E-510 Olympus E-5 Olympus E-M1 Olympus OM-D E-M10 Olympus E-M1 II +9 more
Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow