Digital Camera -- Time Exposures in Night Photography

Discussion in 'Digital Photography' started by Dave, Apr 9, 2004.

  1. Dave

    Dave Guest

    I'm looking at acquiring a digital camera for use in night photography.
    Typically, with my 4 x 5 and Tri-X film at EI of 260, exposures run
    from 5 minutes up to 30 minutes. Now I'm interested in acquiring a
    really good digital, preferably a 35 mm SLR.

    I've looked at all the cameras listed in the April edition of Outdoor
    Photographer. None of them have an exposure possibility of longer than
    30 seconds, including the very high end (i.e., lotsa $$$) Digital SLRs.

    Does anyone know of some way to work around this, or of a camera that
    will give longer exposures, e.g., perhaps up to 10 minutes or so?

    Thanks for your help.

    Dave
     
    Dave, Apr 9, 2004
    #1
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  2. Dave

    Jim Townsend Guest

    Most of the digital SLR's give you a bulb setting.. With a locking
    remote release, you can do easily 5 - 30 minutes. The 300D and D70
    both have this feature.

    The only caveat is that after about 5 minutes, you start getting
    noise in the form of hot pixels. You can still do 1/2 hr, but
    you'll need to do some cleaning.. Dust removal or despeckle
    filters work well for this.

    I did a pretty good 16 minute star trail shot with my 10D..

    http://www.pbase.com/image/20828208

    (Too bad my 50mm f/1.8 lens had a bit of purple fringing :(

    I've never tried, but I doubt you could get useful exposures of
    over 1 hour.. That's one thing film is still better at.
     
    Jim Townsend, Apr 9, 2004
    #2
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  3. Most of the dSLR's have a bulb option.... I'm guessing that given the
    long length of exposure time doing it manually is only
    inconvienient... a few seconds over/under isnt really going to make
    much difference.
     
    Jonathan Wilson, Apr 9, 2004
    #3
  4. Dave

    Dave Guest

    Thanks for the great responses. In looking at the details on several
    mail-order sales sites, a bulb option was not indicated. I've heard
    about the "noise" problem, but also that with digital there's no
    reciprocity failure so exposures are much shorter anyway.
     
    Dave, Apr 9, 2004
    #4
  5. Dave

    Don Guest

    Beyond about 30 seconds or so there is usually little improvement in the
    signal-to-noise ratio with commercial grade CCDs. There are reports that
    the CMOS sensors are somewhat better, but I've also heard some say they're
    worse. You can use very long exposures, but the image usually doesn't
    improve. It is usefull for capturing moving objects such as meteor tracks,
    car headlights, etc. Otherwise you can usually do as well with a 30 second
    exposure and post processing to increase the levels.

    The problem is that the leakage current in the sensor builds up charges with
    long exposures. Usually the rate is slow enough that you don't actually
    saturate the sensor for many minutes. Very long exposures generate more
    photoelectrons, but also more leakage charges. Photreconnaisance cameras
    and astronomical cameras reduce this effect by cooling the focal plane, but
    that's not practical for commercial grade cameras (and may be harmful).

    Don
     
    Don, Apr 9, 2004
    #5
  6. Dave

    Chris Brown Guest

    The Canon EOS digitals have excellent long exposure performance. I've done
    many 10 minute exposures using a 10D, and a few over half an hour.

    You will get a few artifacts in the image with very long exposures, but
    nothing too severe - usually show up as isolated "hot pixels", which are
    trivial to remove if they annoy you.
     
    Chris Brown, Apr 9, 2004
    #6
  7. Dave

    MarkH Guest

    My 10D offers 2 options for over 30 seconds. I can get a remote release
    that can lock the shutter open for as long as I like. I can also get a
    more expensive timed remote which can be set to hold the shutter open for
    as many minutes I like. The timed remote can also do intervalometer
    functions, you could use this if you wanted to take several shorter
    exposures with a few minutes in between to let the sensor cool (like 6
    exposures of 5 minutes instead of one 30 minutes exposure).

    Check www.dpreview.com for details on individual cameras, they usually list
    the cameras shutter speed options. The Canon 10D has this info:
    Min shutter      30 sec + Bulb
    Max shutter      1/4000 sec
    I believe that the site provides this info on a lot of cameras (info found
    on the quick summary of features, there doesn’t have to be a full review to
    get this info)
    Canon G3:
    Min shutter      15 sec  
    Max shutter      1/1250 sec
    No mention of bulb setting here so probably not available.


    BTW
    The smaller sensor on the compact digicams gives higher noise than the
    larger sensors on the interchangeable lens D-SLRs, so you are better off
    looking at a D-SLR for what you want.

    A 2nd hand Canon D60 is also a good option, this camera can take 10 minute
    exposures (and longer) that are incredibly clean, without needing twice as
    long as the exposure time for dark frame subtraction. Some details:
    http://www.dpreview.com/reviews/canoneosd60/page13.asp
     
    MarkH, Apr 9, 2004
    #7
  8. Dave

    eawckyegcy Guest

    You take multiple exposures and stack them. Maybe ~1 minute each?
    You'll have to experiment with the camrea you ultimately choose to see
    what maximum exposure (at what ISO, under what conditions) works best.

    Digital techniques are more flexible than the analog in this area,
    since you have much more control over the "stack" operation. An
    example:
    "Astro Imaging – Capturing Star Trails with a Digital Camera", Peter
    Michaud, Sky&Telescope, 2004 March, p. 126-131.
     
    eawckyegcy, Apr 10, 2004
    #8
  9. This is incorrect. Astrophotographers are using the canon 10d, digital rebel
    for 5-minute and longer exposures with astounding results. e.g.

    http://www.starrywonders.com/dso.html

    http://velatron.com/dca/gallery

    http://clarkvision.com/galleries/gallery.astrophoto-1

    Very long exposures are done by adding multiple exposures together,
    so hours of exposure are done. Adding multiple exposures also reduces
    noise.

    To maximize signal to noise, see:
    http://clarkvision.com/astro/canon-10d-signal-to-noise
    (note the DBN levels given on this page are 16-bit, so 0
    to 65,535.

    Roger
     
    Roger N. Clark (change username to rnclark), Apr 10, 2004
    #9
  10. Dave

    stewy Guest

    What exactly do you want to photograph? At times longer than 5 minutes stars
    will become elongated dots unless you have tracking mechanisms. A few years
    back I got pictures of the aurora using 400asa film and exposures of 60
    seconds. The only problem was the battery in my Canon AE1 froze after 30
    minutes in the -40C temperatures.
     
    stewy, Apr 10, 2004
    #10
  11. Dave

    Dave Guest

    I really appreciate all the postings, and the links were most helpful.
    Some nice work being done with digital and time exposures.

    Does anyone know a work-around to get a bulb-time exposure on a Bronica
    SQB with its normal 80mm lens? The 65 mm lens, yes. My three-year old
    Bronica will not do longer than 8 seconds. Multiple tripping will
    ultimately shake the camera too much. May have to just break down and
    buy a used lens. Sorry, I know this isn't digital.

    Dave
     
    Dave, Apr 10, 2004
    #11
  12. Dave

    Wilt W Guest

    <<Does anyone know a work-around to get a bulb-time exposure on a Bronica
    SQB with its normal 80mm lens? The 65 mm lens, yes. My three-year old
    Bronica will not do longer than 8 seconds. Multiple tripping will
    ultimately shake the camera too much. >>

    Bronica lenses have a way of putting the lens shutter on 'T' (time exposure)
    where no battery power is used to keep the shutter open (which is why the limit
    on B, since that uses battery power). The setting is on the lens.

    --wilton
     
    Wilt W, Apr 10, 2004
    #12
  13. Dave

    JPS Guest

    In message <[email protected]>,
    Perhaps you can use a programmable remote and let it take multiple
    shorter exposures. There should only be a fraction of a second missing
    between each shot when you combine them, and you get a lot less noise
    this way.

    This only works on digital SLRs that don't use dark frame subtraction.
    It may work on non-SLRs if there is no dark-frame subtraction and the
    camera doesn't take long between shots.
    --
     
    JPS, Apr 11, 2004
    #13
  14. Dave

    phil Guest

    Hi Dave,

    I just bought the Nikon 5400 and it has a builb setting and allows
    exposures up to 10 minutes. There are also timed settings that keep
    the shutter open for 30 seconds, 1, 3, 5, or 10 minutes. I have also
    found software that allows me to control the camera with a Palm Pilot.
    It can be found here: http://vyskocil.free.fr/coolcom/

    I used this software with a Coolpix 995 but with the timed settings of
    the 5400 I will probably not use it much.

    The Coolpix 5700 and 8700 also have the longe exposure options. I
    got the 5400 for its wide angle lens and low image noise along with
    low chromatic abberation. I also do travel photography in addition to
    astrophtography so I liked its small size.

    I also looked, salivated, over the D70 but stayed away only due to its
    size. You might also consider the Rebel since from what I have heard
    the CMOS sensor it uses is noise free. Someone please correct me if I
    am wrong on this.

    Cheers,
    Phil Hughes
     
    phil, Apr 11, 2004
    #14
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