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Thread: Extended exposure

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    New Member AdamK's Avatar
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    Extended exposure

    With my 40D I am limited to a 30sec max exposure, as I see most dslr are. So how do you guys do longer exposures than 30sec?

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    Quote Originally Posted by AdamK View Post
    With my 40D I am limited to a 30sec max exposure, as I see most dslr are. So how do you guys do longer exposures than 30sec?
    You have a 'bulb' setting that enables the shutter to remain open for as long as you choose. You will find in your manual how to enable and use it.

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    It's also easier to use a remote shutter release cable, as they usually provide a means of holding the shutter open without you needing to hold anything. It's also important to cover the viewfinder for long exposures because light can get to the sensor via the eyepiece. Canons come with a little rubber thing on the strap for this purpose. Mirror lockup is a good idea for long exposures too.
    Last edited by soulman; 07-10-2012 at 6:51pm.

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    Thanks guys. I'll chek it out.

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    I grabbed a $6 cable remote off ebay for my 40D also works with my 5D, pop the camera on bulb and use the remote and a stop watch to get your times.

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    In addition to the above advice, make sure that you disable long-exposure noise reduction (LENR) in your camera's menu.

    The reason for this comes down to time.

    The LENR feature works by firstly exposing the scene, and then immediately afterwards, making a black exposure (ie, with the shutter closed) for the same length of time, and combining the images using a technique called dark frame subtraction.

    This obviously doubles the amount of time it takes to produce one image, and when the light is changing so rapidly during a dawn or dusk shoot, I cannot afford to lose time. Not only that, but if the image is a dud, I've lost precious minutes and need to shoot again. Additionally, noise reduction is something I'd prefer to do on a much more powerful computer rather than the camera, the latter of which I consider to be a capture device rather than processing device.

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    Ausphotography Regular swifty's Avatar
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    The LENR is mostly useful to reduce hot pixels and amp noise, as oppose to regular noise reduction for ISO gains which are quite uniform throughout the whole image.
    So it can be useful or not, depending on whether your camera suffers much from either hot pixel or amp noise problems. These tend to be non-global phenomena and can be tricky to process out in PP. Eg. I know a D80 suffers from amp noise in the upper corners/edges of frame. I'm unsure about a 40D.
    Nikon FX

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    i agree with swifty, i have used both methods and imo cameras can get better results reducing noise, hot/stuck pixels and sensor anomalies straight from the raw data than post capture programs can.

    further to my own experiences, nikon claims to being able to capture significantly better colours with an in camera multiple exposure using raw data than you can achieve using software, so there is no reason for me to doubt its noise reduction claims
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    If I'm shooting a ten-minute exposure, I'd really prefer not to wait 20 minutes to see if I got it right.

    I see my camera as a capture device. My computer is far more powerful, and I have infinitely more control over the processing.

    Sometimes there just isn't time to wait for the camera to take another long exposure and perform dark-frame subtraction.

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    I agree that there isn't always time, but sometimes there is and it's always good to know one's options. I wouldn't tend to use LENR for a 10 minute exposure either, but 30 sec to 2 min exposures are probably far more common and it's in this range that it can be quite worthwhile as long as nothing is changing too quickly.

    Even if you shoot raw, the camera is never just a capture device anymore. At a bare minimum, the analog signal from the sensor will be be digitised and encoded into the proprietary format used by the camera manufacturer. I prefer to process on the computer as well, but the camera is a computer too now and I don't see any reason not to use the inbuilt processing when it makes sense to do so.

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    Quote Originally Posted by Xenedis View Post
    If I'm shooting a ten-minute exposure, I'd really prefer not to wait 20 minutes to see if I got it right.

    I see my camera as a capture device. My computer is far more powerful, and I have infinitely more control over the processing.

    Sometimes there just isn't time to wait for the camera to take another long exposure and perform dark-frame subtraction.
    yeah agreed, when doing longer than 2 minute exposures or thereabouts it does get mighty annoying waiting for twice as long

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    Ausphotography Regular swifty's Avatar
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    Just to avoid confusion. I'm not saying one should use/not use LENR.
    Just pointing out what it addresses and that it does have benefits depending on make/model/exposure times.

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    Hay Adam, just getting back to your question, there are several good options for cables to fire the shutter for a given time duration.

    If you have a look at a couple of Site Sponsor sites, like Scorptec and Phottix, they will be able to supply you something that will do the job.

    Some now have an inbuilt timer, and will trigger the shutter to even do stacking images, as in shooting star trails.

    Have a lookon their websites mate. Cheap and easy.

    All the techo stuff above is great, but it depends on so many variables when using long exposure, best to just experiment and make a note of what works, settings wise that is, and use this as a starting point for your next outing.

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    Further to this, there are android and IOS apps that will not only trigger you camera, but also do the timing and intervalometer stuff too.

    Some require a cable, others have an infared adaptor.
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    Quote Originally Posted by soulman View Post
    ..... It's also important to cover the viewfinder for long exposures because light can get to the sensor via the eyepiece. Canons come with a little rubber thing on the strap for this purpose. Mirror lockup is a good idea for long exposures too.
    the light enters the uncovered viewfinder and affects the metering module(not sensor), so the exposure will be affected if using a auto or semi auto mode.

    Usually you end up using blub mode only in Manual mode, as the exposure at any of the auto/semi auto modes will be automagic anyhow.

    If Canon DSLR's allow light through the viewfinder, past the raised mirror and onto the sensor, then it's time to change brand!

    So there's another method of achieving a longer than 30sec exposure .. you can use an auto mode and allow the camera to expose the scene itself.
    (it's usually wrong tho as the meter either won't work beyond about -2 or -3Ev).
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    Quote Originally Posted by arthurking83 View Post
    the light enters the uncovered viewfinder and affects the metering module(not sensor), so the exposure will be affected if using a auto or semi auto mode.
    That is correct. I knew you had to cover it, but forgot it was for exposure.

    Usually you end up using blub mode only in Manual mode, as the exposure at any of the auto/semi auto modes will be automagic anyhow.
    Bulb mode is manual by definition given that it's one of the positions on the rotary selector.

    So there's another method of achieving a longer than 30sec exposure .. you can use an auto mode and allow the camera to expose the scene itself.
    Metered modes only go to 30 seconds, on Canons at least, hence the OP's question.

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