E-M1 focus point selection

[Bikie John]

In the thread about lockups, photo_owl makes an interesting comment:

Originally Posted by photo_owl

On the EM's the group points options operate completely differently to the E3/30/5 - in fact they operate the way many people initially (and many still do from discussions) thought the E's did

(The post is here - http://e-group.uk.net/forum/showpost...&postcount=354)

I haven't seen any sort of explanation about how group point selection works - the manual just says something bland like "the camera will automatically select the target". Sadly my technique and understanding are not up to working it out for myself.

Any chance of an explanation? I would be very interested to learn from others' experience as I have tended to stick with single-point AF under the illusion that I understand what it is doing.

Ciao ... John

[Olybirder]

Originally Posted by Bikie John

Any chance of an explanation? I would be very interested to learn from others' experience as I have tended to stick with single-point AF under the illusion that I understand what it is doing.

I do the same thing John. My brief experiments with the nine AF point option indicate that the camera very cleverly selects everything around the subject rather than the subject itself. I suspect that it is not meant to work in that way. I hope you get some useful responses to this thread.

Ron

[photo_owl]

I apologise if my comment confuses any issues re the CDAF on the Pens/OM-Ds!

my understanding is that (ignoring FD) the system has discreet AF sites and, if more than one is active, it will simply select the one where it detects the most contrast. Given a choice mine behaves in the same way that Ron's appears to most of the time!
There's no apparent weighting to the centre of the group. It's primary use is when you only have one target in the area and just want the camera to focus on that - where ever it is in the frame, or most/all of the target is covered by the group and you have sufficient dof that you just want the camera to focus on any of the target within the group, but do it as quickly as possible.

ie it's what people would logically expect an array of live AF points to do.

Diamond on the E3/30/5 works differently. It's both centre weighted and the AF points work together to enable faster focusing than single point can achieve. My point was that some people expected it to work more like that of these CDAF cameras and shied away from it, especially for things like BIF.

[gazza95]

my experience is similar to Ron's

Most of the time I use C-AF and on the E-M1 it will only take picture if it thinks picture is really in focus. Hence why I thought 9 point AF would be useful, Unfortunatel it seems with 9 AF points it does not seem to matter if its the background or foreground thats in focus. Hence why now only use single point AF. A centre weighted option similar to E-3/5 would be VERY welcome.

Gary

[David Morison]

As a time served BIFfer I have now come to the same conclusions and have to think differently to the way I did with the E30/5 so consequently use only small single point for most bird subjects. For BIF however I use single point but magnified to 5x which gives a much larger target area and AFs much faster that centre 9. My tool of choice for BIF though is still Canon 7D which does have a centre-weighted array facility. I do use C-AF Tracking for Landscapes etc. on the E-M1 which enables me to focus on the main subject and then recompose whilst retaining focus with half press.

David

[Bikie John]

Thanks all for your comments, it sounds pretty much in line with my limited understanding. All further comments/experience welcome....

John

[brian1208]

I agree with the "points" ( ) made above on how the 9 box focus selects the high contrast edges and will only use it when I am shooting into uncluttered backgrounds and want to pick up a bird or birds as they enter the EVF.
I usually do this by having the 9 point box centralised vertically but shifted one step to the right or left (depending on which way I expect the bird to arrive) as that lets me pick it up soonest and then I track it to the point at which the interesting action / position occurs. This is usually done with CAF enabled and 6fps

Otherwise its usually small, central single point with SAF (+MF if the light and contrast are bad)

Seems to suit my style of shooting

[Chevvyf1]

Originally Posted by David Morison

As a time served BIFfer I have now come to the same conclusions and have to think differently to the way I did with the E30/5 so consequently use only small single point for most bird subjects. For BIF however I use single point but magnified to 5x which gives a much larger target area and AFs much faster that centre 9. My tool of choice for BIF though is still Canon 7D which does have a centre-weighted array facility. I do use C-AF Tracking for Landscapes etc. on the E-M1 which enables me to focus on the main subject and then recompose whilst retaining focus with half press.

David

YEAH ! David that is what Matt told me to do and I have stuck with these settings 99% of the time

[pault]

Hi, I'm interested in this conversation.
Has anyone considered / tried using "face Detect" set to "on" and "off". My logic being when "on" focus is looking for near subject, not specifically a face, relative to surrounding area. This would be using the "nine" or 81 focus points.
pault

[Bikie John]

David, could you expand a little on this please:

For BIF however I use single point but magnified to 5x which gives a much larger target area and AFs much faster that centre 9.

As I understand it you only have a choice of focus point size with single point, and the only choice you have is Small or unspecified (i.e. normal). I've tried to understand the bit about zoom frame AF in the manual and it doesn't make a great deal of sense. Do you have to magnify the viewfinder display in order to make it effective? How do you manage that when trying to follow a moving subject?

I'm sure birds in flight are more difficult to track than lower-division rugby players so the skills ought to be transferable in my direction

Ciao ... John

[Gwyver]

Originally Posted by David Morison

.... I do use C-AF Tracking for Landscapes etc. on the E-M1 which enables me to focus on the main subject and then recompose whilst retaining focus with half press.

David

David,
Excuse my dimness, but I don't understand this comment. For Landscapes I use S-AF and then recompose whilst maintaining a half press - and this seems to give the expected (focus) result. Is there some advantage to using C_AF + tracking to achieve the same objective?

[David Morison]

Originally Posted by Bikie John

David, could you expand a little on this please:



As I understand it you only have a choice of focus point size with single point, and the only choice you have is Small or unspecified (i.e. normal). I've tried to understand the bit about zoom frame AF in the manual and it doesn't make a great deal of sense. Do you have to magnify the viewfinder display in order to make it effective? How do you manage that when trying to follow a moving subject?

I'm sure birds in flight are more difficult to track than lower-division rugby players so the skills ought to be transferable in my direction

Ciao ... John

With a button assigned to magnify and pressed twice to give a magnified view this is then adjusted to 5x. Pressing the button again removes the magnified view but leaves you with a larger rectangle in the viewfinder in which to frame your moving subject. This is slightly smaller than the centre 9 but in my experience it focuses faster. Although this doesn't seem logical it works in practice and is easier to use on small moving subjects than either 14x single or small single target. The same function is available on the E-M5 and later Pens.

Hope this makes sense!

David

[David Morison]

Originally Posted by Gwyver

David,
Excuse my dimness, but I don't understand this comment. For Landscapes I use S-AF and then recompose whilst maintaining a half press - and this seems to give the expected (focus) result. Is there some advantage to using C_AF + tracking to achieve the same objective?

I'm sorry, I miss-stated this in saying that you have to keep the shutter half pressed. Once you have achieved focus with a half press then the shutter can be released while you recompose and your chosen subject will remain in focus as long as you don't move too far off. After capturing an image and zooming in the chosen focus point will remain centre of screen.

David

[brian1208]

Originally Posted by pault

Hi, I'm interested in this conversation.
Has anyone considered / tried using "face Detect" set to "on" and "off". My logic being when "on" focus is looking for near subject, not specifically a face, relative to surrounding area. This would be using the "nine" or 81 focus points.
pault

I always have it off as I find it both slows down focus and focuses on the wrong subject for my sort of work. (this wasn't done as a deliberate trial but on a few occasions when I have had the problems I mention above I have found that I had inadvertently set face detect on )

[photo_owl]

Originally Posted by David Morison

I'm sorry, I miss-stated this in saying that you have to keep the shutter half pressed. Once you have achieved focus with a half press then the shutter can be released while you recompose and your chosen subject will remain in focus as long as you don't move too far off. After capturing an image and zooming in the chosen focus point will remain centre of screen.

David

following this process the camera will refocus when the shot is taken - I think you were right the first time