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Astrophotography?

Discussion in 'Scenic, Architecture, and Travel' started by TonyTurley, May 28, 2013.

  1. TonyTurley

    TonyTurley TalkEmount Hall of Famer

    Apr 24, 2013
    West Virginia, USA
    Any NEX users having any luck with astrophotography lately? We've had almost constant clouds the past week, and I missed the Venus-Jupiter-Mercury alignment, as well as the moon. Somebody post a photo to cheer me up.

    Tony
     
  2. izTheViz

    izTheViz TalkEmount Top Veteran

    537
    May 10, 2013
    Paris
    Yannis Marigo
    Good question. I was wondering how NEX cameras would perform in Astrophotography.
     
  3. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    I'm more into night landscapes than Astrophotography per se, and I have no shots from the past weeks due to weather, but maybe these will cheer you up a little bit nonetheless.

    <a href="http://www.flickr.com/photos/48126456@N05/8529145729/" title="The power of stars by Poki5, on Flickr"> 8529145729_57291dc171_c. "800" height="489" alt="The power of stars"></a>

    <a href="http://www.flickr.com/photos/48126456@N05/8531627878/" title="The Journey by Poki5, on Flickr"> 8531627878_f5c63de1c9_c. "532" height="800" alt="The Journey"></a>

    <a href="http://www.flickr.com/photos/48126456@N05/8647300670/" title="Blue Desert City by Poki5, on Flickr">"461" height="800" alt="Blue Desert City"></a>
     
  4. TonyTurley

    TonyTurley TalkEmount Hall of Famer

    Apr 24, 2013
    West Virginia, USA
    Thanks Poki, those are excellent. I think I like #2 the most.

    Tony
     
  5. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    Do you mind sharing some of your past night shots?
     
  6. TonyTurley

    TonyTurley TalkEmount Hall of Famer

    Apr 24, 2013
    West Virginia, USA
    Here are a few.

    Tony
     

    Attached Files:

  7. izTheViz

    izTheViz TalkEmount Top Veteran

    537
    May 10, 2013
    Paris
    Yannis Marigo
    Great. Is there any particular technique behind the scene ? I guess long exposure of course but how long to get the stars clearly on the picture Poki ? Any other tip and trick ?
    Thanks guys

    Yannis
     
  8. TonyTurley

    TonyTurley TalkEmount Hall of Famer

    Apr 24, 2013
    West Virginia, USA
    As I recall for my night landscape, I was using the kit SEL1855, and set the camera on M. ISO was 3200, and the aperture was stopped down to f11 to get better DOF. Camera was mounted on a tripod. I adjusted shutter speed until I liked what I saw in the screen. I used the self-timer to make sure I didn't jiggle the camera. I usually bracket my shots, taking several on either side of the "optimum" exposure. Then I look through the images on my PC and keep the best ones.

    Tony
     
  9. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    Stopping down the aperture? Fatal error. That explains why the stars in your shot are everything but good looking (no offense intended!).

    @Yannis: The basic thing you have to understand is how long your shutter speed can be before the stars spread over several pixels and thous form a line and not a point in your photo. The easiest way to calculate this is the 'rule of 500' - simply take 500 and divide it by your 35mm equivalent focal length. For a 24mm lens on a NEX this would mean 500/36 = 13,8 seconds, for example, so once you go over these 13.8 seconds you won't get 'good' stars. This rule is not that exact anymore, and for a NEX-7 or any other camera with such tiny pixels it's a good thing to take some seconds off of that. I could give you the whole formula which includes the pixel size and the speed the earth is moving if you'd like, but I have no time for this right now.

    So, how do you get enough light onto your sensor to see anything on your photos? Simple: Open up your aperture is wide as it goes. Tony's complain about depth of field is irrelevant as stars are at infinite focus anyways. Focusing with E-Mount glass at night can be a bit tricky though. The best solution is to magnify the screen and look for a bright, distant light source (like the north star) and turn the focus ring until it is as small as it gets. Take a test shot and correct your focus if necessary. And, of course, you'll need an ISO level of 800 or higher, depending on your lens and how bright a night is.

    All these things considered, a 24mm 1.8 or faster lens or anything wider than 16mm at f/2.8 are quite well suited for this kind of photography. You can use longer lenses, of course, but this will make things a bit more tricky. The lenses should also exhibit only a modest amount of vignetting as you'll see every stop of vignetting pretty badly in such photos and it's impossible to correct without introducing tons of noise.

    As for the foreground: In most scenes, it won't be out of focus. But it will be too dark in many cases, while any lights (like in my shots 2 and 3) are completely blown out. To get rid of this issue, you need to stack several images in any photo editing app that supports layers and layer masks. For the shots I posted here, I stacked three images for shot number 1 and about 10 for the other two shots to compensate the many differently bright lights.

    But it doesn't stop here. You need extensive post processing to get back the colors of the night sky, which are pretty subtle and - in some cases - even unpleasing otherwise. And you need to do so without getting even more noise in your picture. How this is done? Well, I continue once you tried the rest, it will get a little bit much now otherwise. ;)

    PS: In case you don't think of it - a tripod and a remote (or the 2 sec self counter) are necessary, of course.
     
  10. sleekdigital

    sleekdigital TalkEmount Regular

    135
    May 7, 2013
  11. sleekdigital

    sleekdigital TalkEmount Regular

    135
    May 7, 2013
    I understand the logic for the shutter speed rule, but I think you can generally get away with a small amount of star movement. Many of the really nice milky way pics I have seen are closer to 30s exposures. Granted they might have been using cameras with "larger pixels", but I dunno. I suppose if you just want the brightest stars, the faster shutter speed is better.
     
  12. izTheViz

    izTheViz TalkEmount Top Veteran

    537
    May 10, 2013
    Paris
    Yannis Marigo
    Wow ! Thanks a lot Poki for your detailed feedback. Could'nt imagine those shots would require so much operations. Hard piece of work ! Congrats !

    First, the faster wide I have (16,19 or 24) are 2.8, apparently not fast enough. Could give it a try.
    Second, I am not used to play with layers and masks. Only do some basic to medium post processing tasks in LR or RawTherapee. You mean, you take
    n shots at different exposures and combine them all in PS ? Never done that yet.
    Third, the parisian sky is not
    clear enough. Have to wait for summertime and vacations in Greece to try out something.
    But I'd like to be able to do that
    kind of shot....
     
  13. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    All it does is to automate a job that can simply be done by yourself. And as far as I am concerned, I wouldn't leave any artistic 'guesswork' in the hand of a computer. It's my photo, after all.


    These pics are closer to a 30 seconds exposure because the photographers used much wider focal lengths. For example, with the Zeiss Touit 2.8/12, you can use shutter speeds up to 27,8 seconds. With cameras with larger pixels (for example every 35mm camera with 'only' 24 or less MP) or with a slightly wider lens you could easily exceed 30 seconds. For this reason, it's common to use ultra wide angle lenses for this type of photography. However, the relative illumination isn't any better than with a more than one stop faster 24mm lens.

    To get clear: You can NOT 'get away' with a 'small amount of star movement'. This would be visible on any enlargement - even as small as A4.


    Thanks. Yeah, I do this type of photography for quite a while now and as I'm interested in physics too I did everything I could to get closer to mastering photography under such conditions. I still have lightyears to go, but I get significantly better year by year.

    They are. With a 16mm f/2.8, you probably need to use an ISO value up to 3.200 - but that should be okay, especially if you use one of the newer NEX cameras with the 16 MP sensor. This sensor is almost a stop better in high ISO than the one in my 'ancient' NEX-5, which will make up for this loss of light at least partially.

    It's really pretty easy. Just use the photo which was exposed for the background (i.e. the stars) as the first layer. Then, add a second layer where, for example, a distant mountain is exposed as you wanted it (which usually means a multi minute exposure at small ISO values), add a black layer mask and paint the area you want to use in with a white brush. You can later change the transparency of the layer to change the strength of the effect. Then, let's assume there's a house in there. These lights coming out of its windows will be blown out in these two shots, so add a third layer with a black layer mask and do the same as with the mountain.

    The difficulties are usually come down to these two: Artistically, where you have to choose which light you have to use where to get a natural look (which is the most important thing to keep in mind - if it doesn't look natural, in most cases the photo doesn't end up looking good), and technically, where you need to work pixel perfect to not get any halos or even worse looks. Just magnify to 400% or bigger and work very carefully. Sure, you'll need some hours for every photo to be completely finished, but there's no way around this if you want to get your vision on screen.


    Unfortunately, I have absolutely no experience at photographing night landscapes in bigger cities, thous I can't help you here technically. However I have to agree, the sky in most big cities looks too polluted to get good shots. Also keep in mind that you should seek for a place with the least 'light pollution' (i.e. any artificial lights) to get your shots, except of course if you want to use them artistically and stack them later on.

    Also, bring much time with you. You'll need at least half an hour to take all the necessary photos once you're set the camera up and framed everything, and you'll need some hours in front of your computer screen afterwards. Taking landscapes at night definitely is no 'snapshot' affair. But if you go deeper into it, it's extremely rewarding and it lets you see the world in a different light.
     
  14. TonyTurley

    TonyTurley TalkEmount Hall of Famer

    Apr 24, 2013
    West Virginia, USA
    Here are a couple of late evening landscapes and starscapes from tonight. No PP. The photo with the trees framing Mercury, Venus, and Jupiter was done with a Vivitar 50/1.8; the rest were the Promaster 19-35mm set at f/3.5. That is as wide as it will go. Even with the small community in which I live, there is so much light pollution from other surrounding communities that capturing the band of the Milky Way is nearly impossible. 3200 ISO was as far as I could go without severely washing out the photos.

    Tony
     

    Attached Files:

  15. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    Gratulations, these are already much better than the first ones you posted.
     
  16. TonyTurley

    TonyTurley TalkEmount Hall of Famer

    Apr 24, 2013
    West Virginia, USA
  17. sleekdigital

    sleekdigital TalkEmount Regular

    135
    May 7, 2013
    Any chance that the Sigma 19mm 2.8 can manage decent results? Based on the discussion it sounds like it's not quite wide/fast enough. Would love to hear suggestions for inexpensive lens options for this kind of work.
     
  18. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    Yeah, it's okay. With newer NEX cameras you can get pretty decent results with ISO 3200, which achieves a good exposure together with a 19mm f/2.8 lens.

    Inexpensive, better lens options for NEX? I'm afraid there are none. The only much better options are the Zeiss 12mm f/2.8 and the Zeiss 24mm f/1.8. But of course there are tons of adaptable lenses that fit the bill.
     
  19. sleekdigital

    sleekdigital TalkEmount Regular

    135
    May 7, 2013
    Yeah, I was referring to adapted legacy lenses. I just picked up a Minolta MD 50mm and adapter, so I guess I'll look for something wide/fast for the MD mount.
     
  20. serhan

    serhan TalkEmount All-Pro

    Aug 27, 2011
    NYC