how "quiet" are DSLR's for night photography?

Discussion in 'Digital SLR' started by Scott Speck, Feb 1, 2006.

  1. Scott Speck

    Scott Speck Guest

    Hi Everyone,

    If I'm interested in doing night photography (mostly of distant scenery)
    with exposure times ranging up to 1 minute, I need to know whether a DSLR
    like the Nikon D70 with NR turned on will yield a much cleaner image
    (dark-noise-wise) than a good point/shoot digital with NR noise reduction)
    turned on. Is the difference profound enough to differentiate a great photo
    from a terrible one, or is it barely noticeable?

    I currently have a P/S digital that is hard to get a precise focus on (even
    manually) in really low light, mostly because, when I turn the manual focus
    ring until a distant light source is minimized in size, I'm only able to
    minimize it down to one LCD display pixel, which ends up being too coarse a
    focus when I later view the image on my PC. Or does NR cause loss of
    sharpness that makes it LOOK like it's out of focus? My P/S is a Panasonic
    FZ/30, which I've been placing into "night scenery mode" for night shots.
    In night scenery mode, ISO is fixed at 80, f-ratio is minimized, exposure
    times can be up to 8 seconds long, and NR is turned on.

    When a grad student in astronomy, I used liquid nitrogen cooled and
    thermoelectrically cooled CCD's with a 1.6 meter telescope, and the cooling,
    of course, dramatically reduced dark counts for long exposures (1.5 hours,
    typically). However, I'm not aware of any affordable, portable "cooled ccd
    cameras" that are good for toting around town at night, so I'm assuming that
    isn't an option.

    Thanks in advance for any thoughts,
    Scott Speck
     
    Scott Speck, Feb 1, 2006
    #1
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  2. Scott Speck

    Pat Guest

    I don't have the info in front of me, but I remember reading in a tech
    magazine that Canon was coming out with a tweeked model of one of the
    digital dSLR that was tweaked for astronomy. It was supposed to
    operate better at night, handle low light better, etc. You may want to
    check Cannon's site or check with a major mail order house. I have not
    seen it advertised other than the one magazine. That might be your
    best bet.
     
    Pat, Feb 1, 2006
    #2
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  3. Scott Speck

    Pat Guest

    Pat, Feb 1, 2006
    #3
  4. Scott Speck

    Jeremy Nixon Guest

    The difference is significant, though may largely be due to the inherent
    much higher quality that the D70 will be giving you over a P&S camera.
    I can look at my long-exposure night shots from a P&S, and then from after
    I got the D70, and the difference is immediately obvious even at reduced
    screen-display size. I actually went out and tried to re-do some of my
    shots after getting the D70, because the difference was so great.

    Note that the noise reduction (dark-frame subtraction) reduces fixed pattern
    noise and hot pixels, but does not reduce random noise (and in fact might
    even increase it a bit). Other kinds of in-camera noise reduction are
    best avoided.

    A great method of minimizing noise that is particularly suitable for this
    kind of shot is: take three of the same shot in a row (full exposure,
    whatever you've determined is correct) without moving the camera at all.
    Load all three into Photoshop, make them into layers in the same file,
    adjust the top two layers to 50% opacity, and flatten. This "averages"
    the three images and (using three shots) will double the signal-to-noise
    ratio. The S/N increase goes by square roots, so you would need to
    average nine shots to triple it; three shots is enough for most purposes.
    Obviously if the camera moves at all between shots, the whole thing goes
    down in flames; using the remote control is a good idea for this. And
    switch to manual focus so the camera doesn't re-focus for each shot.
    They need to be identical.

    If you use the above technique you will have no need for additional noise
    reduction of any kind. (Keep the dark-frame subtraction NR on in-camera,
    though.)
     
    Jeremy Nixon, Feb 1, 2006
    #4
  5. Scott Speck

    Toby Guest

    If you want really high quality high ISO performance you should look at
    Canon full-frame (if you can afford it). At 3200 it is much better than any
    Nikon offering. That being said, if you are looking at long exposures at
    lower ISOs the Nikon D200 is supposed to be quite good. Have a look here:

    http://www.naturfotograf.com/D200_rev04.html#top_page

    In answer to your question specifically: I would think that the superior
    circuitry and chip in a DSLR as compared to a point and shoot would result
    in noticeably better long-exposure images.

    Toby
     
    Toby, Feb 1, 2006
    #5
  6. Scott,

    The main difference is in the sensor:

    - the pixels are much bigger, collecting more photons for a given flux

    - they don't have the live preview facility, and are optimised for just
    single-shot images, and not a continuous video feed.

    The comparison is that whereas P&S will go up to ISO 400/800, DSLRs will
    go up to ISO 3200 - for approximately the same noise level in the image.
    Compare the sensitive areas of the "1/1.8 inch" chip and the chips used in
    DSLRs.

    http://www.dpreview.com/learn/?/Glossary/Camera_System/Sensor_Sizes_01.htm

    Not only will the DSLR have a lower noise at a given ISO, you may be able
    to afford faster fixed focal length lenses as well.

    David
     
    David J Taylor, Feb 1, 2006
    #6
  7. The Nikon D70 with NR, works very well for night photography.Vey clean,
    colourful images, with little if any burnout. I have used mine often for
    this, and achieved some sales from the photo library they are lodged with.
     
    Nigel Cummings, Feb 1, 2006
    #7
  8. Scott Speck

    cjcampbell Guest

    The difference is profound. The D70 is typical; there is no need for a
    'tweaked' Canon or any other DSLR. They are very good; better than
    film. If you start doing exposures of 20 minutes or so you will get
    purple noise around the corners of the D70. This disappears with NR
    turned off. The trouble with NR is that it takes as long as does the
    original shot -- an exposure of 2 minutes means NR of two minutes. This
    is because NR works by taking a shot of a black mask with an exposure
    time equal to the photo and then it compares the two. For that reason a
    lot of photographers, including myself, just turn the NR off and remove
    the noise in Photoshop.

    Some of the astrophotographers here have said that DSLRs work better
    for that than film cameras, but I do not do astrophotography at the
    moment.
     
    cjcampbell, Feb 1, 2006
    #8
  9. Scott Speck

    Pat Guest

    I just re-read you posting. The focusing issue is interesting and I
    don't have a quick answer to that. I would suggest you shoot something
    with the lense wide open and then stop it down and reshoot it and
    compare the results. Even at f2 or so, a lense hits "infinity" well
    before hitting "distant" scenery (unless you are using some sort of
    monster lense like a telescope attached to the camera). So focus
    shouldn't be too much of a problem. By setting it to a higher f-stop,
    you'll increase your depth of field and possibly cure the problem. If
    that cures it, then it is a focus problem. But it might not fix it,
    too. It is possible with a P/S camera that you're really taking it
    past it's limits and what you are seeing is not a focus problem but is
    a blur. That could be caused by a couple of things. One could be even
    the slightest of movements. You should be using a good quality tripod
    and probably a rf shutter release to get rid of that. On a windy day,
    you might even want to sand-bag your tripod. On a dSLR, locking your
    mirror up would also help. The other possibility is that the lense
    isn't performing well and you are getting some difraction. I think
    most good-quality SLR lenses probably have better coatings on them than
    P/S camera. If the small light is dead-center, you might also get some
    sort of internal lense reflection that is right on top of the image.

    I am sure that you've already ruled out dust and grime on the lense. I
    am a big fan of filter to protect lenses in most cases, but at night I
    remove them. Also, keep on your sun shade to help block out any
    ambient light that might be sneaking in.

    Finally, where are you shooting this? If it's hot out, you might be
    getting more noise than if you are on an Antartic adventure. If it is
    just after dark, you might also be getting some heat shimmers, too.

    Good luck.
     
    Pat, Feb 1, 2006
    #9
  10. Scott Speck

    phk Guest

    Both the Canon 20D and the Nikon D200 will provide excellent night
    results. You may want to consider a separate power supply or battery
    pack, though, since it takes quite a bit of battery power to hold long
    exposures.
     
    phk, Feb 1, 2006
    #10
  11. Scott Speck

    C J Southern Guest

    Just wondering if the Canon 20Da might be suitable - it's a varient of the
    20D that's tweaked for astrophotography, and is the only dslr that I know of
    that has a live preview.
     
    C J Southern, Feb 1, 2006
    #11
  12. That's a specialised and rather expensive camera - it doesn't have live
    preview but shows (a portion of?) the taking image live. I think that for
    the application suggested, any DSLR will have a most significant
    sensitivity gain over any point-and-shoot. I'll leave it to others as
    which the most suitable DSLR may be.

    David
     
    David J Taylor, Feb 1, 2006
    #12
  13. Scott Speck

    RiceHigh Guest

    The "Noise Reduction" for long time exposure is actually referred to
    the Dark Frame Substraction technique. The tricks is to take another
    picture with the same shutter speed but with shutter closed. This would
    let those hot pixels visilble by the camera and let it rule out these
    hot pixels by simple substraction.

    The noise reduction referred for high ISO pics are something totally
    different. It is a noise filter afterall and will smooth out the noise
    and soften the picture image. In contract, the Dark Frame Substraction
    technique will increase noise as noise can be doubled in extreme case
    of substraction where the brightest and darkest pixels can add to the
    most difference.

    To eliminate hot pixel, the best way to shoot at a higher shutter
    speed. Here is an example of mine. The picture was taken with my
    ancient DC Olympus C-3000 which will have many hot pixel and fading of
    colors for longer exposure time:-

    http://www.geocities.com/ricehigh/Gallery/pano3456small.jpg

    Best Regards,
    RiceHigh
    http://www.geocities.com/ricehigh
     
    RiceHigh, Feb 2, 2006
    #13
  14. Scott Speck

    Paul Furman Guest

    Here's something much less elegant on an oly C3030:
    http://www.edgehill.net/2001-leonids.jpg

    Things have improved a lot since then!
     
    Paul Furman, Feb 2, 2006
    #14
  15. Scott Speck

    C J Southern Guest

    It allows you to preview the centre 20% or 5% (selectable) - which would
    help incredibly with his focusing problems (that's what it's designed to
    do).

    I didn't think it would be his first choice either, but a budget wasn't
    mentioned, and the gentleman did mention being a "grad student in
    astronomy".
     
    C J Southern, Feb 4, 2006
    #15
  16. Scott Speck

    w.beckley Guest

    I do terrestrial night photography with exposures of 30 seconds quite
    frequently with great results. I'm using a Canon 20d. I used to have a
    Canon G series and the 20d (and the D70 that I had between the two)
    beats the pants off of the G. That said, I think the 20d beats the D70
    in this application, but that's me and my bad experiences with noise on
    the D70.

    The problem that you get into is that raw exposures (you'd be shooting
    raw, right?) do better when slightly overexposed, but noise increases
    pretty dramatically as exposure time increases...there's a point of
    diminishing returns that I have yet to isolate even for my own work. I
    still shoot a number of exposures at different settings and sort it out
    later.
     
    w.beckley, Feb 4, 2006
    #16
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