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Olympus OM-D E-M5 Mark II The first OM-D's successor.

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Old 20th January 2016
Stuart444 Stuart444 is offline
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What's a focus clutch? And how can I guarantee a focus on infinity?

Two questions where you guys could help me, please.

I've noticed on my latest firmware upgrade I've got a new option in menu/gearA/MF clutch (the last one in the menu list).
What is this? I've googled and found discussions but they are not very helpful when the basic concept isn't explained. What does it do? Is it just for certain lenses? (I don't have any Pro series lenses)

I discovered it when trying to solve a problem that others might have an answer to. In certain situations I'd like to force the camera to focus on infinity, or the hyperfocal point, I don't mind which. What I don't want is the camera to autofocus as it tends to prefer closer focus points, and I don't want the focus ring to work as if I focus on infinity manually then any slight nudge on the focus ring spoils it. I discovered on my previous Panasonic G3 that you can focus "beyond infinity". This seems to be true of my Oly lenses too. In the "old days" (pre auto focus), lenses had a hard stop on infinity which was great when conditions made it difficult to focus by eye and you just wanted to know it was on infinity. I see some modern lenses also have this, or appear to as they have a focus scale on the barrel, but none of my Oly lenses have it, they just have a free-running focus ring.

Thanks for any help.

Stuart
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Old 20th January 2016
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Bikie John Bikie John is offline
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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

To answer the first question - some of Oly's lenses, including the 12-40 f/2.8 and the 40-150 f/2.8, allow you to slide the focussing ring forwards and backwards. In the forward position the lens works as a normal AF lens, or you can set it to manual focus in the menus. When you slide the ring back it uncovers a distance scale and the lens will only work in manual focus.

I think Oly's name for this is something like "snap focus" and some people like for applications like street photography. However it can cause problems if the ring moves when you're not expecting it, and you wonder why it is refusing to auto-focus. There are lots of threads on here from people who have worried that their lens is broken because they haven't twigged what's happened - I am a fully paid-up member of the "snap focus ring dummies club"

As I understand it the option appeared in the latest firmware upgrade and allows you to disable the snap focus function, so you will get normal AF regardless of the position of the ring. I'm not sure how useful it is - if you have never had the problem you are unlikely to set it, and if you have you are very likely to remember it!

As for the second question, I'm not sure. I think that turning a lens to the hard stop for infinity does not always work, as some lenses were deliberately designed to focus "beyond infinity" to allow for temperature changes.

John

Last edited by Bikie John; 20th January 2016 at 10:55 AM. Reason: Correct mistake
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Old 20th January 2016
Ricoh Ricoh is offline
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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

Quote:
Originally Posted by Bikie John View Post

...

I think Oly's name for this is something like "snap focus"..

...some lenses were deliberately designed to focus "beyond infinity" to allow for temperature changes.

John
'Snap-Shot' I recollect, but could be wrong of course.

'Focus beyond infinity' - presumably to allow the control loop to slighty overshoot when acquiring focus, otherwise the poor electric motor would stall.

IMHO the true benefit of manual focus is only rewarded if you can see both the distance and the aperture setting when glancing down at the lens, plus the DoF scale of course.
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Old 20th January 2016
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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

This is a interesting issue that you have raised. I think camera development has focused too much on AF means.

The issue of focus at "infinity" is a critical one for astrophotography. AF does not work good enough to focus on stars. I end up using Olympus capture in MF mode and driving the focus ring from there. All lenses I have focus "beyond infinity" a concept I think only Douglas Adams could explain. However I do note the position on the lens that gives me a close approx for focus to those distant stars. The FT 9mm-18mm lens is the best lens I have that will give good results focus by turning the focus ring to the infinty stop. The problem is with zoom lenses the focus to infinity point has a different focal point position depending on focal lenght.

How many lament the loss of the scales you used to get on lens barrels. I had a Oly bridge camera about 10 years ago and there was viewfinder option to drive the focus using a distance scale. Out of all the new features I would like to see on a next gen camera is one that has some form focus ability driven by distance. My dream would be a device that calculates (low powered laser) the distance your object is from the focal plane and sets the lens to the focal point and tells you what that distance was.
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Old 20th January 2016
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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

I am going to try out a Bahtinov mask on my Olympus to get perfect infinity focus on stars.
They are commonly used on telescopes and there is no reason they won't work on a camera lens if you magnify the image on the rear LCD.

Have a look on YouTube to see how they work.
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Old 20th January 2016
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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

If you are up for a bit of DiY, you can Make your Own

There's also a "Lord Mask" which may be easier to make HERE

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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

Quote:
Originally Posted by Graham_of_Rainham View Post
If you are up for a bit of DiY, you can Make your Own

I will give it a go.

Thanks very much
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Old 20th January 2016
Stuart444 Stuart444 is offline
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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

Thanks for your information. I can't understand why manufacturers release firmware upgrades without issuing an information sheet to help users get the best out of it. Anyway, it doesn't affect me and my lenses then.

I'm not photographing stars, I'm trying to take air to ground photos from a little single seat aircraft where the Oly with 12-50mm lens is big given the little space I have in the cockpit! It worked OK, but stopping the auto focus from focussing on the canopy or wings was hit and miss, so I tried manual but struggled to get it focussed in that situation. At home I tried the landscape scene setting but the focus system still operates (why??).

I can understand why they would need to provide "past infinity" focus as part of the autofocus system. But you'd think that when it's on manual focus, this would be suppressed as the need to find the focus point obviously has gone then. Then we could just turn the focus ring a decent amount in the requisite direction and we'd have infinity set.

I have a Nikon bridge camera which gives visual indication of its focus distance, I'd forgotten about that. Perhaps it will do a better job.

Or maybe I need to look for an older lens that only has manual focus. However I would need the other usual Oly functions, and ideally this sort of zoom range. I wonder if such a lens exists. I agree, they've concentrated on the gizmos they can add to the "benefits" list of new cameras, but not necessarily provided kit that works in real life situations.

Cheers

Stuart
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Old 20th January 2016
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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

Hi everyone!

I find that all my legacy lenses focus past infinity - at least in visible light - my belief was that this was to allow infra red photography (many also have a red mark next to the white for ir work). If I ever need to focus on infinity I tend to pick the most distant thing I can see, focus on that then flick to manual focus to lock, but this wouldn't stop you knocking the focus ring - I would suggest using a wide rubber band on the edge of the focus ring to stop it moving accidently.

Cheers,

Ralph.
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Old 20th January 2016
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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

You're testing my memory, Ralph, but didn't lenses with an IR focus mark have it on the "inside" of infinity, and the lens was focused on infinity for visible light if turned to the mechanical stop but "beyond" infinity for IR in that position?
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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

What do you fly Stuart? When I did a bit myself, I loved the high wing Cessna for aerial 'togging, just open the window. I flew other types too, but the high wing was the preferred tool for photography.
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Old 21st January 2016
Stuart444 Stuart444 is offline
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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

I have a Corby Starlet, so once you know that you can pin me down to one of four in the UK! Mine is G-CCXO. Yes, high wing without a strut and no doors or a good window is best, but it's Hobson's choice - the Starlet is a brilliant little aircraft for cheap fun flying and was chosen for that, but alas (for photography) low wing. In the summer I can fly open cockpit so that's one problem out of the way - a bit cold for that now, though.

Anyway, I've been checking out my more humble Nikon P-500. On manual focus, you can drive it to infinity using its rear control dial whilst watching the focus scale on the screen- no "past infinity" to worry about. And it stays set - no focus ring to accidentally knock and alter the setting. Looks like the better tool for the job. I'll try it next flight.

Olympus please take note! If others can do it, so can you!
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Old 21st January 2016
Petrochemist Petrochemist is offline
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Re: What's a focus clutch? And how can I guarantee a focus on infinity?

Quote:
Originally Posted by Stuart444 View Post
You're testing my memory, Ralph, but didn't lenses with an IR focus mark have it on the "inside" of infinity, and the lens was focused on infinity for visible light if turned to the mechanical stop but "beyond" infinity for IR in that position?
The IR focus mark could be on either side depending on the lens make up.

As I believe was mentioned up thread, many lenses went beyond infinity to allow for expansion (generally this is with longer focal lengths, all my 300, 500 & 600 mm lenses go beyond, the 600 at least doesn't have an IR focus mark) & these days AF ones generally go beyond to prevent motor damage.

My Panasonic cameras automatically take native lenses to infinity when turned on. Shame mine are all slower zooms, the ones I really could do with it on are all adapted.
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