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How do you know how many seconds … minutes??

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    Mozzytheboy
    Mozzytheboy e2 Member 3550 forum postsMozzytheboy vcard United Kingdom3 Constructive Critique Points
    30 Dec 2012 - 5:42 PM

    Reading my new book I got regarding photography it makes mention over and over about long exposures from say two seconds to twenty minutes. What puzzles me is when he says 90 secs or 19 seconds; how on earth do you know? I cannot get my head round that one so thought I'd ask those that will know. Oh I searched but got nowhere Sad

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    justin c
    justin c  104504 forum posts England36 Constructive Critique Points
    30 Dec 2012 - 5:52 PM


    Quote: how on earth do you know?

    In one word Histogram. Take a test shot and then use the histogram to check your exposure.

    To get a rough starting point, say for instance, you're doing some night photography and your camera indicates that a correct exposure would be 30 seconds @ f5.6 @ ISO 800, but you want to use a larger aperture, or perhaps a lower ISO setting. You set the camera to B (bulb) mode and end the exposure yourself when the correct amount of time has elapsed. So, for instance, going on the settings mentioned above, ISO 400 would require 60 seconds, ISO 200 would require 120 seconds, ISO 100 would require 240 seconds, etc. etc.

    User_Removed
    30 Dec 2012 - 5:56 PM

    Basically Mozzy...

    Experiment matey!! Take one exposure @ 'x' seconds/minutes (view results) then one @ 'y' seconds/minutes and again... (view results). Then 'fine-tune' in from your observed results.

    Remember this though... with looooong exposures, the 'write time' (the amount of time the camera takes to write the data to your card) will also increase dramatically to that you (may?) have experienced in 'normal' light conditions.

    Have fun Mozzy!! Wink

    Last Modified By User_Removed at 30 Dec 2012 - 5:56 PM
    steveh5
    steveh5  270 forum posts United Kingdom
    30 Dec 2012 - 7:59 PM

    After a long exposure many cameras take a second image with the shutter closed, this is then used to process the image and remove dead/hot pixels from the final image. On my D80 I turned it off and the only difference it made was the data write time returned to normal. It is worth checking if you can do this and try it, The great advantage with digital is the instant review while you are there not 2 weeks later, experiment and read the manual for options.

    Steve

    User_Removed
    30 Dec 2012 - 8:13 PM


    Quote: On my D80 I turned it off and the only difference it made was the data write time returned to normal.

    You sure about that Steve...??

    That option is off on my D300 - and the write time is as I said... increased.

    (It's the same on my D70, Olympus E-P1 and E-PM2 also Wink )

    Last Modified By User_Removed at 30 Dec 2012 - 8:15 PM
    discreetphoton
    discreetphoton Site Moderator 93427 forum postsdiscreetphoton vcard United Kingdom20 Constructive Critique Points
    31 Dec 2012 - 9:25 AM

    That's correct Mike, turning on Long Exposure Noise Reduction results in longer waits between photos. I'm also using a D300.
    I never found the feature necessary on this camera, but with the D80 I'd see the benefit seven on a 30 second exposure. Mine was terrible for night shots. The corners always suffered from latent heat build-up.

    JJGEE
    JJGEE  96098 forum posts England18 Constructive Critique Points
    31 Dec 2012 - 9:59 AM


    Quote: After a long exposure many cameras take a second image with the shutter closed, this is then used to process the image and remove dead/hot pixels from the final image

    Is this implying that the camera takes 2 raw images, processess / combines them in camera to produce, in effect, a 3rd raw file for saving to the card ?

    Mozzytheboy
    Mozzytheboy e2 Member 3550 forum postsMozzytheboy vcard United Kingdom3 Constructive Critique Points
    31 Dec 2012 - 10:41 AM

    You see, it was worth me askingWink

    Jestertheclown
    31 Dec 2012 - 11:54 AM

    I was Mike.
    I`m intrigued by this 'multiple raw' idea. It'something of which I've never heard.
    I shall be interested to hear what others have to say about it.

    User_Removed
    31 Dec 2012 - 3:26 PM

    My understanding of Long Exposure Noise Reduction is that a second "mirror-down" exposure is made so that only the noise is recorded. That noise is then removed from the first exposure, leaving a (somewhat) less noisy original.

    But on D300, D3s and D800 I have never felt that I needed to use it - at least not at the cost of having to wait twice as long to view the image or histogram in the LCD.



    Mozzy - get hold of an iPhone app called LongTime which is great for calculating the length of exposure required when you stick an ND filter in front of the lens.

    Last Modified By User_Removed at 31 Dec 2012 - 3:29 PM
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