I wonder what they mean by the MO focus switch setting?

[Dazz1]

I wonder what you make of this option on my new Sigma 150-600mm lens?

Here's the description from Sigma, about the use of the focus switch. I know you can depress the shutter button halfway, let it autofocus, then tweak the focus manually using the focus ring - but this can be done when the switch is in the AF position. Don't see what MO adds to that.

...and then I can't make sense of the line "With AF position, standard full-time manual focus is available." except that it also seems to indicate the MO switch is superfluous.

[hide][top]Manual override incorporated to make two full-time manual modes switchable

In addition to AF/MF, MO (Manual Override) is incorporated as one of the options of the focus mode switch.
By setting it to the MO position, it switches to manual focus by rotating the focus ring even during continuous AF.
With AF position, standard full-time manual focus is available.
Using the optional SIGMA USB DOCK, it is possible to adjust the MO position’s sensitivity to switch to manual focus.

[ameerat42]

(Clearly, Wets has not read the book - And I can't find an on-line version, so I can't help)

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This is all I could find. Search on MO.

It seems to indicate that it "should" be in MO mode before you try to MO the focus. (But???)

[Dazz1]

(Clearly, Wets has not read the book - And I can't find an on-line version, so I can't help)

The "book" is a pamphlet and doesn't make a lot of sense either. I'll quickly type it out...

The lens also permits manual focussing even in the autofocus mode. With the camera set to the One-shot AF (AF-S) mode, it is possible to manually override the autofocus while the shutter release button is pressed halfway.

Also this lens can offer [Full-time MF function] (Manual Override) by rotating the focus ring of the lens while autofocussing is in operation. ForFull-time MF, set the focus mode switch on the lens to the "MO" position.

[ameerat42]

Yes, it clearly means:

--Or something like that. Have been looking since you posted. Nothing specific.

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Some more refs:
http://www.sigma-global.com/en/lense.../features.html
and
http://www.sigma-global.com/en/lense.../features.html

[Cage]

Good luck sorting that lot out.

How some instructions can complicate what is probably a simple operation, to activate a simple function, is beyond comprehension.

OK, have you tried all three settings? Reading the above instructions it seems like the "MF' mode is superfluous.

[ricktas]

Seems to me it has a fairly obvious use

AF (full auto focus)
MO (autofocus with ability to manually over-ride)
MF (full manual)

So in AF, the lens autofocuses
In MF, the lens has to be focused manually using the focus ring
In MO, you can press the shutter button half way, to engage autofocus, but then you can use the focus ring to adjust the focus point yourself..if you want to.

[Cricket]

yep MO = manual override

[ameerat42]

Correct, but how it's distinct from the other methods of obtaining same is what Wets is asking - and me too now

[Cricket]

I am not very knowledgeable with technical stuff but I am sure I read somewhere once that it was not advisable to manually focus a lens whilst the camera was in AF mode. I agree it is nice to be able to use auto focus and then tweak the focus but I read damage could be done in AF mode. It looks like Sigma has come up with a manual override in order to auto focus then tweak the focus without causing damage and without going back and forth to manual focus and auto focus.

[ricktas]

Correct, but how it's distinct from the other methods of obtaining same is what Wets is asking - and me too now

Cause as said ^ in some systems trying to adjust focus on a lens when it is in AF mode can cause damage to the AF motors etc.

My thoughts on this for real world usage...you are trying to capture a bee on a flower with macro. AF is good, but the bee keeps moving and your focus is off slighty. MF takes longer to get the bee in focus. MO, means AF onto the bee and then you can make micro adjustments to focus manually to make sure even if the bee moves, you can keep it in focus. AF sometimes 'hunts' when it goes to focus, and thus using AF on the bee means it can unfocus completely if it hunts, and you miss the shot you wanted.

[Dazz1]

Cause as said ^ in some systems trying to adjust focus on a lens when it is in AF mode can cause damage to the AF motors etc.

My thoughts on this for real world usage...you are trying to capture a bee on a flower with macro. AF is good, but the bee keeps moving and your focus is off slighty. MF takes longer to get the bee in focus. MO, means AF onto the bee and then you can make micro adjustments to focus manually to make sure even if the bee moves, you can keep it in focus. AF sometimes 'hunts' when it goes to focus, and thus using AF on the bee means it can unfocus completely if it hunts, and you miss the shot you wanted.

No, sigma actually tell you to manually adjust the focus when in AF mode. As I posted, straight from the manual...

The lens also permits manual focussing even in the autofocus mode. With the camera set to the One-shot AF (AF-S) mode, it is possible to manually override the autofocus while the shutter release button is pressed halfway.

So given that, why do we need a special switch position to allow the same thing?

[Cage]

This reminds me of a Sigma 150mm f2.8 Macro I had in my Pentax days. A brutally sharp lens, but also had some very weird instructions about focusing.

Concerned me enough that I only ever used manual focus, even when not doing macro.

Sorry, I'm not being helpful, merely commiserating.

[Dazz1]

This reminds me of a Sigma 150mm f2.8 Macro I had in my Pentax days. A brutally sharp lens, but also had some very weird instructions about focusing.

Concerned me enough that I only ever used manual focus, even when not doing macro.

Sorry, I'm not being helpful, merely commiserating.

and thanks for that It isn't a biggie, just got to wondering what the extra switch position did for me. I have been using the lens, and even fine-tuning the auto-focus since I got it. There's no danger of damage, you can tell it disengages the motor or something - it's not like trying to focus a Canon kit lens that you left in AF by mistake

[ameerat42]

LATE NEWS...
Wets. Enquiries elsewhere have yielded only one, rather perfunctory, reply. Ie, not very informative.

I think you'll have to be the pioneer here.

[arthurking83]

....

The lens also permits manual focussing even in the autofocus mode. With the camera set to the One-shot AF (AF-S) mode, it is possible to manually override the autofocus while the shutter release button is pressed halfway.

....

What I'm thinking is:

In AF-S focus mode, if you have the camera setup(as most folks do) to expose on AF confirmation then it could make a bit of a difference to the way MO works.
Firstly: on the camera you may have a choice of priorities when in AF-S mode: 1. release(or shutter) priority or 2. focus priority.
That is, the camera will allow you to take the exposure even if AF hasn't been set(yet) in 1. This allows you to keep on spraying .. long after you've stopped praying!
If OTOH, you use 2. mode, where the priority is on AF, if you don't achieve focus the camera will not expose, allow exposure or even respond to heavier pushing on the release. It feels like the camera is locked(it's not, that's the way it works).

So if you get focus, and then tweak focus a bit, in release priority mode(2.) the camera will lock up again. It knows that focus is no longer set, so you need to start the AF acquisition process again.

I don't have this lens so can't confirm, but ... this MO mode seems to indicate that if you set the lens to MO mode, you may be able to still make exposure even if you have no reset the AF confirmation point.

Someone with a camera that allows exposure priority settings in AF-S mode.

I'm assuming that MF mode is simply manual only and no AF at all.

Would be interesting to see if this is the way it works.

[Dazz1]

What I'm thinking is:

In AF-S focus mode, if you have the camera setup(as most folks do) to expose on AF confirmation then it could make a bit of a difference to the way MO works.
Firstly: on the camera you may have a choice of priorities when in AF-S mode: 1. release(or shutter) priority or 2. focus priority.
That is, the camera will allow you to take the exposure even if AF hasn't been set(yet) in 1. This allows you to keep on spraying .. long after you've stopped praying!
If OTOH, you use 2. mode, where the priority is on AF, if you don't achieve focus the camera will not expose, allow exposure or even respond to heavier pushing on the release. It feels like the camera is locked(it's not, that's the way it works).

So if you get focus, and then tweak focus a bit, in release priority mode(2.) the camera will lock up again. It knows that focus is no longer set, so you need to start the AF acquisition process again.

I don't have this lens so can't confirm, but ... this MO mode seems to indicate that if you set the lens to MO mode, you may be able to still make exposure even if you have no reset the AF confirmation point.

Someone with a camera that allows exposure priority settings in AF-S mode.

I'm assuming that MF mode is simply manual only and no AF at all.

Would be interesting to see if this is the way it works.

Ahaa! Yes! I did notice today that the camera would not fire after I manually tweaked the focus, until I tweaked the focus to point where I got it to beep.

So, experimenting with the switch if the AF/MO positions - that seems to be the difference.

In AF mode, if you depress the shutter button halfway and it doesn't focus (no beep), then tweak the focus manually, it still won't take the shot until you get it to beep by tweaking the focus until the camera agrees that it is in focus.

In MO mode, if you depress the shutter button halfway and it doesn't focus (no beep), then tweak the focus manually, it will take the shot no matter how badly you have set the focus.

[arthurking83]

....

....
In MO mode, if you depress the shutter button halfway and it doesn't focus (no beep), then tweak the focus manually, it will take the shot no matter how badly you have set the focus.

Aha! good to know.

(hopefully) a quick story.

My first cameras was a D70s, and like I said in another post, my primary interest was landscapes.
With the D70s, you had to set the camera to AF-C mode if you used AF to initially acquire focus, but then wanted to alter focus slightly say for hyperfocal(or whatever).
AF-C mode has it's drawbacks tho, and in some situations focus trap can be a good way to achieve perfect focus in fast paced situations instead(of AF-C).

So if I had the camera set to AF-S, it was a clunky operation to reset the camera every time I wanted to prefocus or something but then tweak focus later.
I'd be forever mucking about with the small focus mode switch(labelled CSM) to switch between each mode to get the camera to work.
The actual issue was that the D70s doesn't have the release priority mode option in it's menu feature list.

Needed a D200 for that. Coupled with many other feature gripes of the D70s compared to the D200 .... I made the decision to update, just as the D300 was announced!(got the D300 instead )
Something as simples as landscapes and focusing wherever I wanted was never as easy by comparison .. dunno how I persisted for that year and a bit with the D70s.

But like I said, that ability to use AF-S and focus priority is also handy at times, eg. I found with tracking birds actually(with my way too short 70-200).

So it seems that MO would be my primary choice of lens mode, just for that ability.
That is, the lens still AFs as you need it too, you stay in AF-S mode with focus priority(when needed) but you can always tweak or whatever the focus to suit(say if the lil takcer is hiding amongst twigs and stuff and the camera NEEDS to focus on twigs only .. and not birds! )

In other situations where you need AF-C(tracking ability) then this is a different mode altogether and is used for other situations.

I don't have a Nikon lens with a similar mode system, but some Nikon lenses have a dual manual-auto switch. That is they have a MA mode or a AM mode(as well as the M mode)
I assume that the M/A mode is similar to the MO system on this lens .... where it has a manual priority mode that works the same way, and the A/M mode is probably the opposite way around.
Like I said tho, no experience with them tho.

[Dazz1]

So it seems that MO would be my primary choice of lens mode, just for that ability.
That is, the lens still AFs as you need it too, you stay in AF-S mode with focus priority(when needed) but you can always tweak or whatever the focus to suit(say if the lil takcer is hiding amongst twigs and stuff and the camera NEEDS to focus on twigs only .. and not birds! )

In other situations where you need AF-C(tracking ability) then this is a different mode altogether and is used for other situations.

Yes, I think MO may be my primary mode from here in. I don't use tracking much at all, and as you say, another whole different kettle of fish.

[J.davis]

wetpixels, do you not use Back Button Focus, its ideal for tracking moving things (flying birds).

[Dazz1]

wetpixels, do you not use Back Button Focus, its ideal for tracking moving things (flying birds).

Tried it once when I first got the camera. Didn't like it then, but, yes, maybe I should give it another go.