Focusing at infinity at night (OMS e-m10, 14-42 kit lens).

Cowpoke

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Ok I'm new to non point and shoot cameras (and night photography), so apologies if this is a dumb question.

How do I focus at infinity at night if I want to capture stars, meteors etc without there being anything really bright enough for the camera to auto focus on, or me to really judge doing so manually? The manual focus ring doesnt stop at the extreme focus distances, it just keeps spinning, so its difficult to judge when I'm fucussed out as far as I can go.

Lowering my aperature will obviously give me a wider focus range, but will let less light in. I guess I could use the moon to set my manual focus, but is there any other trick?

Thanks!
 

randyspan

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Set manual focus to "magnify" and "peaking". I have been able to focus this way, using mars as my infinity focus point, even at 14mm.
 

Cowpoke

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Set manual focus to "magnify" and "peaking". I have been able to focus this way, using mars as my infinity focus point, even at 14mm.
Thanks Randy, what does the peaking do? I've seen it in the settings, but havn't played with it. I have played with the magnify and it helped with some brighter lights.
 

randyspan

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Peaking when in focus make the area look white (configurable). Hard to explain, but you will know when it is in focus!
 

Petrochemist

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Certainly not a dumb question.
No peaking available on any of my cameras. Nailing focus in low light is never easy,
The best advice I've seen is to focus before it gets dark, switch to MF and make sure you don't knock the focusing ring. I'm never that organised, so either focus on the moon (ideally there wouldn't be one), or find my stars are fuzzy blobs.
 

Klorenzo

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Just one question: what's wrong to just turning the focus ring for a while in the correct direction? Eventually you'll reach the maximum point, don't you?
 

Ross the fiddler

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Using magnified view will also help if there is something to see sufficiently & also with Live View Boost on to help which can be set in Menu * D (see Pages 141 & 91 of the full PDF manual).
 

LowriderS10

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Definitely not a dumb question...this is actually one of my few complaints about the system...without an OVF and with focus-by-wire lenses, infinity focus at night is a massive pain in the neck.

Turning it the correct way 'till it tops out doesn't really work, because most lenses will focus beyond infinity (yeah, I know...sounds ridiculous, but true).
 

Klorenzo

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I have read that focusing on the stars works fine, never tried myself. I think that activating all the AF zones could help to pick up any star that is bright enough.
 
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I'm hoping to get some Milky Way shots during my upcoming beach trip so this is interesting but also confusing to me -- is this an issue because of infinity calibration? Meaning that on some lenses focused all the way out may not = infinity? Thx.
 

Cowpoke

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Just one question: what's wrong to just turning the focus ring for a while in the correct direction? Eventually you'll reach the maximum point, don't you?
With this lens at last there is no "all the way" the ring just spins and spins focusing back and forth. It doesnt stop.

So if 1 is close and 5 is iinfinity, spinning it and spining it would focus like 12345432123454321.
 

Klorenzo

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With this lens at last there is no "all the way" the ring just spins and spins focusing back and forth. It doesnt stop.

So if 1 is close and 5 is iinfinity, spinning it and spining it would focus like 12345432123454321.
I think it works this way: if the sensor detects a clockwise movement it increase focus, otherwise it focus closer.
It does not matter when the ring is, there are not special positions.

At least it never happened to me to focus too much and suddenly find that I am on the other extreme of the focus range. If you have doubts about this you could make this quick test.
 

Petrochemist

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I have read that focusing on the stars works fine, never tried myself. I think that activating all the AF zones could help to pick up any star that is bright enough.
Trouble is the only star that's bright enough is the sun. (Unless a star goes nova at just the right time)
 

Petrochemist

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My G5 has a focus scale on the LCD during manual focus. It has a mark at about infinity but goes significantly beyond. The position for infinity is about 5/6 of the way along the scale from closest.
Using cowpoke's 1 to 5 scale it goes 123456.
The positions beyond infinity might be useful in unusual situations (Taking images in infra red, or when using extension tubes/close up filters, or even perhaps just when temperatures are extreme).
 

LowriderS10

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I've tried focusing on stars...doesn't work. Even turning to MF and magnifying has turned out to be fruitless. This may be because I'm in an area with lots of pollution (Korea), so stars are dimmer, so I think MF *MIGHT* work if you're in a dark enough area, where the stars are brighter (providing your AF system with more of the much-needed contrast it feeds on), but I doubt any of our cameras would be able to AF on a star (other than the Sun, and I wouldn't suggest that haha).
 

lightmonkey

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at night, theres so much contrast between the stars and background everything sorta glows and its hard to see the peak rim. i use magnification and lcd. even so, the fly-by-wire focus sensitivity is so much that its hard to "lock it in". [wish there was firmware option to reduce the focus throw!!!]

anyway, i tried to grab the moon and the few shots i got were due to some patience and lots of LUCK.


e.g., this is with 40-150mm lens, and took about 20 shots to get 3 focused ones
Subscribe to see EXIF info for this image (if available)
supermoon, on Flickr
 

Klorenzo

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Trouble is the only star that's bright enough is the sun. (Unless a star goes nova at just the right time)
I think this is just not true: I can easily see the stars with my eyes so I suppose the camera can see those too.

As I told you this was given as an advice in a similar thread from a person who actually used it. Maybe he was speculating or lying.

Anyway it's easy to find out if it works or not. Also see the lightmonkey response.
 

Petrochemist

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I think this is just not true: I can easily see the stars with my eyes so I suppose the camera can see those too.

As I told you this was given as an advice in a similar thread from a person who actually used it. Maybe he was speculating or lying.

Anyway it's easy to find out if it works or not. Also see the lightmonkey response.
I've tried it often enough!
Cameras have a minimum threshhold for AF which is well below what they can record (or you can see). It may be in perfectly clear skies the milky way as a whole is OK, certainly even the best conditions I've found in the UK there's not a chance!

If your camera is linked to big enough telescope, the light gathering power could be enough to autofocus, no standard lens will be likely to manage. (I've not personally tried anything faster than f/1.7 my fastest AF lens)

Typical exposures for starry skies (EV-4 at best) are ~2s at f/1.4 & iso 1600. So there's not a lot for the AF to work with. Most cameras AF systems give up about EV-1 from the spec's I've seen.
 

Klorenzo

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I've tried it often enough!
Cameras have a minimum threshhold for AF which is well below what they can record (or you can see). It may be in perfectly clear skies the milky way as a whole is OK, certainly even the best conditions I've found in the UK there's not a chance!

If your camera is linked to big enough telescope, the light gathering power could be enough to autofocus, no standard lens will be likely to manage. (I've not personally tried anything faster than f/1.7 my fastest AF lens)
Ok, you were talking about AF, I was thinking about focus in general. I added the AF part later, without thinking too much about that.
So stars are bright enough to focus on, not enough for AF. But this works badly anyway due to EVF/LCD problems and focus-by-wire.
 
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