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Thread: Moon focusing

  1. #1

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    Moon focusing



    I hope I post this the right place.

    I have a problem. I was shooting the moon using auto-focus and it focused so the image looked good in the finder, but the slides where not sharp. I noticed later that my lens wasn't focusing at infinity when it focused on the moon, and that is weird. I have done a manual focus shot at the moon, but are waiting for the film to be developed. The image in finder was then blurred. I wonder what the slide will be like.
    Why is my camera being fooled by this? It normally focuses perfectly.

    Can any of you give me advice on moon focus? And perhaps on exposure. I shot the moon with an exposure calculated from the following:

    Shutterspeed = 1 / film speed (I use 90 and 125 with Fuji Sensia 100)
    Aperture = 8 or 11
    (or a faster speed and a wider aperture)

    Is my calculation right?

    Greetings Morten

  2. #2
    dogea's Avatar
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    What I know, is that the auto-focus works better with lot of light. During night shots it is allways better to use manual settings, or you will get a very strange behaviour of the lens.

    Usually, when I take night pictures, I try to work with the greater aperture as possible, but something very important, is the use of a tripod.

    Last but not least, to take a picture of the moon, I'll use a tele-photo lens. I use a Sigma Mirror-Telephoto FD 600mm 1:8, with a Tamron SP F System 2x Tele-Converter. The result is great, but the shutter must be opened quite a long time.

    I hope the results of your next film will be good.

    Best Regards,


    David

  3. #3

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    Quote Originally Posted by dogea
    but something very important, is the use of a tripod.
    I did not use a tripod but I used a 300 mm tele and exposed this way:

    1/500 @ f/5.6

    Is that still too slow to handhold when shooting the moon?

  4. #4
    dogea's Avatar
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    I guess. I really think that 1/500 is too quick, I will use B-shutter, and try different times.

    Tele absorb a lot of light (at least my mirror tele), slow shutters fit better, but again, the use of a tripod becomes mandatory.

    Best Regards,


    David

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    Quote Originally Posted by dogea
    I guess. I really think that 1/500 is too quick, I will use B-shutter, and try different times.
    The amount of light is ok @ 1/500, f/5.6. The moon is having nice tones and is fully detailed. I have tried shooting the moon at 20 second f/22 and 20 seconds f/32, and the moon ended up being a white circle.

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    127
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    I did a moon shot recently (on 35mm aaarrghhh!).

    I used an 800mm lens (400+2x teleconverter). Any shorter and it would have been tiny. At 800 it was a decent size, but could have been larger.

    The lens was set at f5.6, so thats f/11 with the converter. With 400 colour film I shot frames at 0.5 and 1 second. Both came out nicely (I haven't checked the negs as I just put the film through a local lab, and it came bacl fine).

    Ian

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    "I did not use a tripod but I used a 300 mm"

    There's your answer to the image being not sharp. Regardless of shutter speed, it's tough to hand-hold a 300mm lens and expect tack sharp images.

    The Moon is in full sunlight, so there's plenty of light on the subject. There is a common modification to the "Sunny 16" rule for shooting the full Moon - f/11 at 1/ISO. 1/500 at f/5.6 is close enough, maybe a little underexposed.

    Most lenses have extra room past the "infinity" setting to allow for expansion/contraction of the system at the temperature extremes.

    Your autofocus system might have problems because the full Moon is inherently low contrast - there are no shadows from the craters and other surface features because it is in direct overhead lighting.

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    Quote Originally Posted by Dave Mueller
    Your autofocus system might have problems because the full Moon is inherently low contrast - there are no shadows from the craters and other surface features because it is in direct overhead lighting.
    So the conclusion must be to manual focus at infinity, use a tripod and expect
    tack sharp slides?

    Morten

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    Ed Sukach's Avatar
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    Kind of a strange topic... I'll usually expose for those as I do for the rest of the model...

    I'll join in with one word of advice ... NEVER "moon" a rhinoceros!!!
    Carpe erratum!!

    Ed Sukach, FFP.

  10. #10

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    While it sounds like most of your sharpness issue may be related to hand-holding the 300mm lens, don't forget that the moon is a moving object. Motion is magnified along with the image when using a long lens.
    My Verito page

    Anyone can appreciate a fine print. But it takes a real photographer to appreciate a fine negative.

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