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Thread: Help me focus at night

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    neverhood311's Avatar
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    Help me focus at night

    I just got back from a mid-semester vacation to San Diego and snapped a few photos while I was at it. I went to Coronado at night and, from there, you can get a great view of the downtown skyline across San Diego Bay.

    I had my camera on my sturdy Manfrotto 190XPROB with the 496RC2 ball head to be sure there was no vibration. Also, I had the legs on their shortest setting and the center column was not extended more than a few inches. And yet, about half of my photos of the nighttime skyline came out blurry. The first one was sharp, and the next one was very blurry, followed by a handful of almost sharp photos. Each time, the camera reported that it had focused (although I wasn't looking through the viewfinder to see exactly what; I was using a remote cable release). However, NOTHING in the out-of-focus photo IS in focus.

    Is there some sort of limitation on focusing with night photography, even if a part of the image is bright (the bright city lights)? And once I finally figure out how to get good focus every time, what can be done about the blown-out highlights in the city lights? HDR?

    Help me focus at nightHelp me focus at night

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    Re: Help me focus at night

    Quote Originally Posted by neverhood311 View Post
    Is there some sort of limitation on focusing with night photography, even if a part of the image is bright (the bright city lights)?
    Make sure that you set your autofocus point to one of the bright light sources. Cameras generally need a lot of contrast to focus accurately. There's a lot more on this in the tutorial on camera autofocus. I'd also recommend turning off autofocus once you've achieve a focus lock. This way you can recompose later without also causing your camera to mis-focus (if/when your camera's autofocus point is no longer aimed at a bright light source). If there are no bright light sources and your subject is very distant (such as in the example you've provided), then the moon can also be a good way to set your focusing distance. You might also want to try manually focusing by looking at the rear lcd screen (in live view and full magnification). Hope this helps!
    Last edited by McQ; 16th November 2010 at 10:02 PM.

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    Moderator Donald's Avatar
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    Re: Help me focus at night

    Justin

    Good to see you back again. Been wondering where you were!

    I'll defer to someone who knows more about long exposure work to offer explanations as to what may have gone wrong. Did you switch onto manual focus once you had got the first one focused, and leave it on manual after that?

    But, I will add that your image brings back happy memories of being over there looking back at the city. That was in 2002.

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    Re: Help me focus at night

    Hi Justin - welcome back

    Short answer is "don't use AF at night".

    Turn on live view - zoom in to one of the light sources - and adjust the focus until the light source is as small as possible.

    "Job Done"

    Note: Depending on brand, you may need to switch your lens to MF mode.

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    Shadowman's Avatar
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    Re: Help me focus at night

    I understand that you should not use vibration reduction either if using with a tripod. I've only had a few opportunities to try it without but cannot really see the difference. One thing I have noticed is that my Nikon D60 focuses very slowly on bright objects. The 50mm f/1.8 lens helps a lot. I would also try using an aperture of f/22 for overall sharpness and shorter duration shutter speed.

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    Re: Help me focus at night

    Quote Originally Posted by Shadowman View Post
    I understand that you should not use vibration reduction either if using with a tripod.
    Just for the record - with Canon equipment - some IS units are tripod aware, and some aren't.

    I would also try using an aperture of f/22 for overall sharpness and shorter duration shutter speed.
    F/22 will give you a longer duration shutter speed

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    Re: Help me focus at night

    Quote Originally Posted by Colin Southern View Post
    Just for the record - with Canon equipment - some IS units are tripod aware, and some aren't.



    F/22 will give you a longer duration shutter speed
    You can set the shutter speed manually for a shorter duration.

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    neverhood311's Avatar
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    Re: Help me focus at night

    Whoa, I didn't realize that my absence was so noticed, haha. School started back in August and I've got quite a heavy homework load and not too much time for leisurly photo-taking.

    Excellent suggestions.

    Little by little I'm learning to check and make ABSOLUTELY sure that IS is turned off before using a tripod. In this case, it was turned off.

    LiveView sounds like perfect for nighttime tripod shooting. Too bad my Rebel XTi is too old-school for that.

    And I later realized that some of you would probably cringe when you saw that I did a landscape shot with an aperture of f/4 That's another habit I need to break.

    I'll definitely put the manual focus trick into practice.

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    Re: Help me focus at night

    Quote Originally Posted by Colin Southern View Post
    Short answer is "don't use AF at night".

    Turn on live view - zoom in to one of the light sources - and adjust the focus until the light source is as small as possible.
    What about cameras that do not support live view ?

    This has been a head ache for me and I still have not found a good solution

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    Re: Help me focus at night

    Hi Justin,

    You might also want to put your shutter release on a time delay setting of say 5 seconds, if you do not have a cable or other automatic release system. Pushing the shutter, even on the tripod, can cause camera shake and a 5 second delay will allow the camera to settle.

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    Moderator Donald's Avatar
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    Re: Help me focus at night

    Quote Originally Posted by Shadowman View Post
    You can set the shutter speed manually for a shorter duration.
    John

    Is the point not that you need a longer shutter for, say, f22 than you would for, say, f11? Otherwise you're not going to get the correct exposure.
    Last edited by Donald; 17th November 2010 at 07:28 AM.

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    Re: Help me focus at night

    Quote Originally Posted by Steaphany View Post
    What about cameras that do not support live view ?
    Upgrade

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    Re: Help me focus at night

    Quote Originally Posted by Donald View Post
    John

    Is the point not that you need a longer shutter for, say, f22 than you would for, say, f11? Otherwise you're not going to get the correct exposure.
    Donald,

    The scene similar to Troy's, multiple light sources night photography.

    When I set my camera to aperture priority and use F/22 it automatically sets the shutter speed at 30 seconds. It overexposes the image, all the lights in the windows and at street level are blurry but the buildings look relatively sharp. If I try to compensate by using exposure compensation I lose detail in the buildings. So if I decrease the shutter speed by half I can get more sharpness in the lights and maintain the detail in the buildings.

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    Re: Help me focus at night

    One thing that I have done with astrophotography is study the histogram.
    How it works is, the more focussed a star is, the smaller the area of sensor that the light gets to. As the light coming in has a constant intensity, the smaller the area the brighter the image. This translates into a spike on the histogram, which gets more "spiky" and moves further right for a better focus.
    Hope I've explained it well enough?

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    Re: Help me focus at night

    Hi Justin...

    Here is a shot of the San Diego skyline from the Coronado Ferry Landing.

    I shot using the following parameters...

    Mirror lock-up - I always use this when I am shooting non-moving subjects at night

    Aperture priority F/stops were 2 stops or so below the maximum - using a 200mm f/4L IS lens that would have been around f/8.

    -1 EV exposure control

    AEB + or - 1-EV

    NOTE: In using any type of auto exposure at night, my 30D will usually over expose since it wants to bring the black sky up to a gray. In reducing my exposure by one stop and then shooting with AEB of +1 or -1 stop the resultant exposure comes out to be: -2 stops, -1 stop and as the meter reads. Most often one of these three exposures is pretty well dead on. However, occasionally, I will do a HDR composite of the three shots.

    ISO around 400 - I don't like exposures that are extremely long

    Auto focus

    Mirror lock-up... note: when using mirror lock-up the camera will shoot individual shots, even if it is in the burst mode.

    Remote shutter release used - this keeps the camera from moving due to finger pressure on the shutter release button

    BTW: When selecting AEB, the camera default setting is to revert back to normal (not bracketed) exposure whenever the camera is turned off or when the battery is replaced. My x0D model cameras have a custom function that overrides this default setting and allows the camera to stay in the AEB mode when the camera is turned off. This is the setting I have my cameras at because I like to be the one to decide how my camera shoots and not give that control over to the camera. I am not sure whether or not the xx0D (Rebel) series cameras have this custom function. If not, just be sure you turn on the AEB whenever you want to use that mode.

    The x0D cameras have a custom function to reduce noise at longer exposures. I will usually select this function. I will also use a noise reduction software of some type.

    Help me focus at night

    Here are shots of Hong Kong Harbor, hand-held around 1/25 second @f/2.8 using ISO 800. Canon 30D camera with 17-55mm f/2.8 IS lens. Lens had IS turned on and the exposure was one of a series of +1 or -1 stop bracketed exposures. I used auto focus and shot over the heads of the Chinese crowd in front of me.

    [Help me focus at night

    Help me focus at night
    Last edited by rpcrowe; 17th November 2010 at 04:43 PM.

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    Re: Help me focus at night

    Quote Originally Posted by Colin Southern View Post
    Upgrade
    The Sigma SD1 will probably not be available for a few years, Oh well, just more reasons to head back to film.

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    Re: Help me focus at night

    Quote Originally Posted by JonathanC View Post
    One thing that I have done with astrophotography is study the histogram.
    How it works is, the more focussed a star is, the smaller the area of sensor that the light gets to. As the light coming in has a constant intensity, the smaller the area the brighter the image. This translates into a spike on the histogram, which gets more "spiky" and moves further right for a better focus.
    Hope I've explained it well enough?
    Excellent tip !!!

    Thanks

  18. #18
    neverhood311's Avatar
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    Re: Help me focus at night

    Quote Originally Posted by Colin Southern View Post
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    Haha, if only it were that easy. Give me a few years to finish school and get a real job then we'll talk.

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