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Thread: Focusing troubles for night time shots

  1. #1
    XSi 88's Avatar
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    Focusing troubles for night time shots

    Hello,
    I was looking for any advice I can get on acheiving better focus at night. I have tried setting my lens to manual and turning the ring all the way to the right for infinite focus but that seems to still give me blurry areas. I have also tried using a flashlight on the subject then auto focusing and swithcing to manual so it doesn't change but that seemed to give me the same result. I am setting my f stop at 11 and using a tripod but i can never seem to get the whole frame in focus. Could someone please help? thanks.

    XSi 88

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    Re: Focusing troubles for night time shots

    Hi "XSi 88"

    Just a couple of questions for you ...

    1. What are you shooting at night?, and

    2. What camera are you using?

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    Moderator Dave Humphries's Avatar
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    Re: Focusing troubles for night time shots

    Quote Originally Posted by Colin Southern View Post
    Hi "XSi 88"

    Just a couple of questions for you ...

    1. What are you shooting at night?, and

    2. What camera are you using?
    I think I can guess A2; a Canon XSi

    I would also ask;

    3. what focal length are you shooting at?

    4. what range of distances are you hoping to get sharp?

    5. can you post an example image?

    6. could you tell us a first name and put it in your profile under "Real Name"? (thanks)

    Some ideas to be going on with ...

    With a known focal length, crop fator and aperture - a quick peruse of a Depth of Field calculator should give a "hyperfocal" distance to manually set focus at.
    Setting focus to infinity is something I would never do because:
    a) it wastes over half the depth of field - it is split (very roughly) 40%/60% in front/behind the set focus point
    b) some lenses focus past infinity (watch out Buzz LightYear) and, combined with a), makes it even worse

    Welcome to the CiC forums from ...
    Last edited by Dave Humphries; 13th March 2011 at 12:18 PM.

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    Re: Focusing troubles for night time shots

    What are the subject elements within the field of view that correspond to the positions of the camera's focus sensors ?

    Most cameras set the focus by adjusting the lens until this sensor region gains the highest attainable contrast differences. ( Computationally quick ) This means gradient and soft edged subjects can be hard to focus irregardless of the ambient light level. Point light sources also become problematic since there is no vertical or horizontal edge for the sensor to act on. Note: Some camera employ sensors which require an edge of a specific orientation to derive an accurate focus.

    Here is a software tool you may want to consider:

    DSLR Focus

    It is a tool designed to allow astro photographers to, depending on camera and telescope/lens, automatically or manually focus the image based on the image characteristics of point light sources. There should be no reason why this can't find applications in terrestrial night and low light photography.
    Last edited by Steaphany; 13th March 2011 at 01:49 PM. Reason: typos

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    Re: Focusing troubles for night time shots

    To get the field of view for a landscape to be 0 blur you will need more like an f15-f20 but for most purposes perfect clarity is not required for every object. I find it even distracts from the picture many times. That said in a few days I will post some night shots I took yesterday.

    -Sonic

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    XSi 88's Avatar
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    I am shooting at different landscape scenery and I am using a canon rebel XSi.

    I have been trying a focal length between f8 and f11 and an iso of 200. I will gladly post something for you, just let me look through my photos.

    I am going to go out this weekend and try some shots with the full moon so I will post those as well. Is it best to try and capture photos at dusk or dawn when it is still a little light out?

    Here is one pic i took at night notice how the head on the gator is blurry.it seems like the camera focused on it's back.

    5514420285_62a75e9939_b.jpg
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    Last edited by Colin Southern; 16th March 2011 at 07:27 AM.

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    Re: Focusing troubles for night time shots

    Hi Jeff,

    Quote Originally Posted by XSi 88 View Post
    Is it best to try and capture photos at dusk or dawn when it is still a little light out?
    Ususally yes, it is.
    Although even when the sky might look very dark to you, it can come out quite bright in a photo if the exposure is set for the landmass, but don't leave it too late, within an hour after sunset/befores sunrise is the normally recomended timing, but Colin does it for real, so be guided more by his advice than mine on this.

    Quote Originally Posted by XSi 88 View Post
    Here is one pic i took at night notice how the head on the gator is blurry.it seems like the camera focused on it's back.

    5514420285_62a75e9939_b.jpg
    Which focus point was in use?
    Did you attempt to focus on the nose/eyes with a single, central focus point, hold focus with half shutter depress, then recompose?
    If the answers are "don't know" and "no", then the following applies...

    AF relies on detecting contrast and the nose is in shadow, but the back isn't, so left to its own devices, the camera is going to focus on the most contrasty and well lit bits - in this case, the back.

    This will then be made worse when you sharpen the picture because that also will work on the brightest and most contrasty parts best. You could PP the picture selectively to enhance the exposure and contrast of the head before sharpening to alleviate that effect.

    If the 'gator was on the move, a shot taken a little earlier, with head in the light (such as it is), would have given a much better result.

    Cheers,

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    Sonic4Spuds's Avatar
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    Re: Focusing troubles for night time shots

    Jeff,

    Yes it did focus on the tail, the easiest way to remedy this problem is to focus manually. The wide depth of field here makes the leaves on the left really distracting, and I would say use a smaller f-number for the aperture.

    As to the time to shoot, I think it is best whenever you are out there; but to be practical, whichever gives you the best scenery with the moon.

    -Sonic

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    XSi 88's Avatar
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    Re: Focusing troubles for night time shots

    this pic was taken when it was very dark out. I used the flashlight technique to obtain focus then went to manual. my shutter speed was at 30 seconds so that may have contributed to the head blurr. i was usinig the center focal point and was trying to focus on the head region. Thanks for the tips i am going to try with some inanimate objects this weekend. I try the 1 before daylight and darkness and see what happens. Thanks.

    Jeff

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    XSi 88's Avatar
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    Re: Focusing troubles for night time shots

    thanks for the advice. I will try manual focus next time I get the chance.

    Jeff

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    XSi 88's Avatar
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    Re: Focusing troubles for night time shots

    I will ask a silly question. my camera f-stop will go up to f22, but the lens is max of 5.6. Should I be using a different lens with a higher f-stop? I'm not really sure how the two work together.

    Thanks

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    Re: Focusing troubles for night time shots

    What! No one asked why there was an alligator on the sidewalk???

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    Re: Focusing troubles for night time shots

    Quote Originally Posted by MiniChris View Post
    What! No one asked why there was an alligator on the sidewalk???
    That's obvious Chris, Both Jeff and you are from Florida and we all know you can't walk anywhere in Florida without meeting a 'Gator.
    Last edited by Steaphany; 16th March 2011 at 01:11 PM. Reason: typo

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    Moderator Dave Humphries's Avatar
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    Re: Focusing troubles for night time shots

    Quote Originally Posted by XSi 88 View Post
    this pic was taken when it was very dark out. I used the flashlight technique to obtain focus then went to manual. my shutter speed was at 30 seconds so that may have contributed to the head blurr. i was usinig the center focal point and was trying to focus on the head region. Thanks for the tips i am going to try with some inanimate objects this weekend. I try the 1 before daylight and darkness and see what happens.
    Ah, I obviously under estimated what you'd already done.
    At the risk of annoying it, I wonder if 'painting' the head with torchlight might have helped even up the exposure - or just added to the problems because it would be a different colour light to the (probably sodium vapour) sidewalk lamp.

    Cheers,

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    XSi 88's Avatar
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    Re: Focusing troubles for night time shots

    I am going to try to get photos of a statue with the full moon behind it when it is very big and low in the sky. To get the moon and the statue into focus do I have to take multiple shots with my focal point on the moon and then the statue and then use software to do focal stacking or is it possible to get both in one shot . Hopefully I can time it in the morning around dawn since I live on the west coast of Fl.

    Thanks
    Jeff

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    Moderator Dave Humphries's Avatar
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    Re: Focusing troubles for night time shots

    Quote Originally Posted by XSi 88 View Post
    I am going to try to get photos of a statue with the full moon behind it when it is very big and low in the sky. To get the moon and the statue into focus do I have to take multiple shots with my focal point on the moon and then the statue and then use software to do focal stacking or is it possible to get both in one shot . Hopefully I can time it in the morning around dawn since I live on the west coast of Fl.
    Hi Jeff,

    Before you go, do have a read of these tutorials;
    Understanding Depth of Field
    Understanding the Hyperfocal Distance

    The moon is at infinity, the statue rather closer, using one of the Depth of Field calculators, you will be able to find out the answer to your question there yourself - I can't answer it because you haven't given me enough information.

    You can enter details like lens aperture, focal length and camera to statue distance.
    Your camera is the default "1.6X" type, so just leave that option where it is.

    Cheers,

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    XSi 88's Avatar
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    Re: Focusing troubles for night time shots

    I just want to say thanks for the tips I went out this weekend and took some early morning pics and they turned out really well. I think I will post one in March's Competition. Thanks again for all of the help everyone!

    Jeff

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    Re: Focusing troubles for night time shots

    Quote Originally Posted by XSi 88 View Post
    I will ask a silly question. my camera f-stop will go up to f22, but the lens is max of 5.6. Should I be using a different lens with a higher f-stop? I'm not really sure how the two work together.

    Thanks
    I notice that no one specifically addressed your question, here. You probably have already figured this out by perusing the mentioned tutorials, but I'm going to give you my 30 second tutorial on f:stops.

    As with most number series used in cameras, f:stops work backwards. The smaller numbers give a larger hole for the light to enter the camera and, thus allow more light in. So, on your lens, f:5.6 is the largest hole you can get to let in light and f:22 is the smallest hole you can get to let in light.

    If you want my treatise on why numbers work backwards in photography, just ask.

    Pops

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    XSi 88's Avatar
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    Re: Focusing troubles for night time shots

    Thanks, That makes sense, I wasn't sure if that meant the range was 5.6 and lower (bigger). Thanks for the advice I appreciate it very much.

    Jeff

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