My OM1 won't change focus mid-shooting in CF with SH2 etc. What am I doing wrong?

[jonnyapps]

Hi all,

I'm keen to understand better what I'm doing wrong. I'm doing a test pointing at a distant subject, holding down the shutter button, then retargeting to a closer subject mid-burst.

Throughout, I keep the focus (back button) held down.

As soon as I release the shutter button, the camera re-focuses.

My expectation is that it should refocus between shots mid-burst, but it isn't doing so.

Where am I going wrong?

I'm using the OM1, 300mm F4, manual mode with Auto ISO and experimenting with the various shutter modes except the one that specifically states it won't re-meter or focus between shots.

Thanks very much in advance.

 

[Skeeterbytes]

It can, hard to say why it's not. I use shutter half-press focusing and the camera follows moving subjects in SH2.

I don't use BBF and perhaps continually pressing the AF-on button is impacting focus behavior. There is a setting AF/2/3rd item that offers two priority chalices. Have never experimented with that.

Good luck figuring it out.

Rick

 

[drj3]

The OM1s only scan once when you half press the shutter button (you can set the E-M1s to rescan with mode 3).

They will refocus on targets with visible detail as the target changes distance.

They can also jump focus to closer or more distant targets which are close enough to the focus distance for some detail to show.

They will be more likely to jump to a new distance with C-AF sensitivity at +2 but still will not jump focus when you point at a new target with no detail.

They are more likely to change focus with wider aperture lenses and when illumination is very different.

They are also somewhat more likely to change focus using the normal burst mode with IS Priority, possibly because the frame rate is much slower.

The Olympus E-M1s are more likely to change focus in this situation, since they use previously exposed frames to judge and modify (predict) focus since they could not focus quickly enough to maintain focus on fast moving targets changing distance. However, this also made them much more likely to jump focus from a target to a background if you failed to keep the focus points on the target.

The OM1s are far more likely to retain focus on the target and change focus on the target as it moves quickly since targets normally cannot change distance so much that there was no detail on which the camera could focus between frames. The OM1s do not appear to use prior exposed frames to predict focus.

--
drj3

 

[Danielvr]

Are you using plain C-AF, or C-AF+Tr ? Are you using subject recognition? Anything else that might affect what the camera thinks is your target an whether or not it should be kept in focus?

Personally I'm not familiar with the OM-1 and it's AF-system, but my expectation with any camera in C-AF mode would be that when I aim it a different target half-burst, I'd have to briefly release and re-press the AF button to get it to lock onto it. Basically, C-AF deals with moving targets, not moving photographers.

 

[jonnyapps]

Sorry for the delay in replying and thank you everyone for your helpful comments.

I've only just now had a bit of time to test this further.

It seems it works as expected with the 300mm F4 on its own - I can pick a distant target (a rooftop) hold the shutter down and move rapidly to a much closer target (a bush) and it refocuses as expected.

However, with the MC-20 teleconverter added in, it doesn't refocus. It doesn't hunt at all, it just doesn't change focus...

If I focus on a distant target, hold the shutter, and slowly adjust my aim (top of roof slope /\ to bottom of roof slope), then it does refocus with the MC-20. It's only if I switch target distance rapidly that it seemingly gives up.

Thanks again.

 

[Box Brownie]

Sorry for the delay in replying and thank you everyone for your helpful comments.

I've only just now had a bit of time to test this further.

It seems it works as expected with the 300mm F4 on its own - I can pick a distant target (a rooftop) hold the shutter down and move rapidly to a much closer target (a bush) and it refocuses as expected.

However, with the MC-20 teleconverter added in, it doesn't refocus. It doesn't hunt at all, it just doesn't change focus...

If I focus on a distant target, hold the shutter, and slowly adjust my aim (top of roof slope /\ to bottom of roof slope), then it does refocus with the MC-20. It's only if I switch target distance rapidly that it seemingly gives up.

Thanks again.

I cannot speak about your precise findings but one review about OM and the various long lenses was that he found when using the MC20 convertor, that the AF performance was more sluggish. Especially in low light conditions e.g. comparing either sunny/bright overcast to shaded (in tree line?) areas.

His conclusion was if in subdued light don't use the MC20

 

[Skeeterbytes]

Sorry for the delay in replying and thank you everyone for your helpful comments.

I've only just now had a bit of time to test this further.

It seems it works as expected with the 300mm F4 on its own - I can pick a distant target (a rooftop) hold the shutter down and move rapidly to a much closer target (a bush) and it refocuses as expected.

However, with the MC-20 teleconverter added in, it doesn't refocus. It doesn't hunt at all, it just doesn't change focus...

If I focus on a distant target, hold the shutter, and slowly adjust my aim (top of roof slope /\ to bottom of roof slope), then it does refocus with the MC-20. It's only if I switch target distance rapidly that it seemingly gives up.

Thanks again.

Are lens FW up to date? They got one when the MC20 was released.

Rick

 

[jonnyapps]

Sorry for the delay in replying and thank you everyone for your helpful comments.

I've only just now had a bit of time to test this further.

It seems it works as expected with the 300mm F4 on its own - I can pick a distant target (a rooftop) hold the shutter down and move rapidly to a much closer target (a bush) and it refocuses as expected.

However, with the MC-20 teleconverter added in, it doesn't refocus. It doesn't hunt at all, it just doesn't change focus...

If I focus on a distant target, hold the shutter, and slowly adjust my aim (top of roof slope /\ to bottom of roof slope), then it does refocus with the MC-20. It's only if I switch target distance rapidly that it seemingly gives up.

Thanks again.

Are lens FW up to date? They got one when the MC20 was released.

Rick

An excellent thought that got me checking, but yes, fully up to date!

 

[David5833]

I tested my OM-1 and it does the same thing with the 300mm lens and may be a bit worse with the 1.4 TC added. It seems more likely to respond when the change in distance is small and the new target is complex, but in some cases it does fail to adjust, as you found. Setting CAF sensitivity to +2 seems to help, but not dramatically. A nearly foolproof workaround is release and repeat but that shouldn't be necessary. However, I've used sequential shooting with real world subjects moving quickly toward or away from me and haven't noticed the CAF simply refusing to adjust as it sometimes does when going back and forth from different subjects and distances. I'm sure there would be situations where it would make a difference, but I can't recall experiencing them.

 

[jonnyapps]

Thank you for testing, and apologies for the delay in replying.

Good to know I'm not mad at least!

 

[drj3]

I tested my OM-1 and it does the same thing with the 300mm lens and may be a bit worse with the 1.4 TC added. It seems more likely to respond when the change in distance is small and the new target is complex, but in some cases it does fail to adjust, as you found. Setting CAF sensitivity to +2 seems to help, but not dramatically. A nearly foolproof workaround is release and repeat but that shouldn't be necessary. However, I've used sequential shooting with real world subjects moving quickly toward or away from me and haven't noticed the CAF simply refusing to adjust as it sometimes does when going back and forth from different subjects and distances. I'm sure there would be situations where it would make a difference, but I can't recall experiencing them.

The OM1s scan only once when you initially half press the shutter button. They will not scan again if you point them at something which shows no detail in the EVF. It does not rescan and it does not know if it should focus closer or farther away.

OM Systems could add a scan function to rescan if there is no detail, but this has the danger of rescanning again in the middle of a burst should you momentarily point the camera where it can see no detail. It would be very rare for anything you are shooting to change distance sufficiently that the camera would see no detail, so the rescan would probably cause more problems while solving a non-existent one.

If you want to see how the camera focuses without a scan go to the Menu - AF - Screen 4 and turn off the AF Scanner. Now half press the shutter button and move the camera to targets at different distances. It will only focus if you point it at something with some detail so that the camera knows how to move the lens to focus. This is how it functions after the initial scan while you half hold the shutter button.