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    My Eyes Over Any Camera
    By Enrico Uva | February 29th 2012 12:40 PM | 14 comments | Print | E-mail | Track Comments
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    About Enrico

    After majoring in chemistry at Concordia University I worked briefly at Fisheries and Oceans' Arctic Biological Station and in the food industry...

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    My daughter took this recent picture of me shoveling the snow off my deck. I've always been intrigued by how, compared to an average camera, the eye does a much better job of handling the perception of color and detail of objects in front of the sun. The digital appearance of the scattered snow is darker and fuzzier than what I perceived it to be. Several orange hues and the glittering of fine particles have not been captured.

    Similarly it takes a good quality camera, the proper filter and some adjustments to reproduce the full color and glimmer of foliage that's in between direct sunlight and the photographer, something that our eyes and brain do so automatically. Moreover, if you are literally and severely myopic, and you place yourself in the same position and stare at the spaces between leaves, the circular gaps between broad leaves oscillate, and the individual leaves seem to blend into a single heaving tapestry. Trying to reproduce that effect with either a film or still camera is a challenge that I have not seen anyone surmount. Attempts to use filters and purposely unfocus don't come close to revealing the beautiful illusion.

    Comments

    MikeCrow
    A lot of this is the dynamic range of recording materials/processing (film or silicon), if you look for High Dynamic photography you can find examples that are much more like what you're looking for.

    Most digital cameras have 12/14 bit adc's, 16 bit adc's help.
    This site has a lot of information on dynamic range.
    —
    Never is a long time.
    Mi Cro | 03/01/12 | 09:19 AM
    UvaE
    A lot of this is the dynamic range of recording materials/processing (film or silicon), if you look for High Dynamic photography you can find examples that are much more like what you're looking for.

    Thanks, Mi. Those are impressive.
    Enrico Uva | 03/01/12 | 12:41 PM
    rholley
    I also find Mi Cro’s links very informative.

    It seems that noise in digital photography is something one has to live with.

    This is the moon last night, 1st March 2012

    —
    Robert H. Olley Quondam Physics Department University of Reading England
    Robert H Olley | 03/02/12 | 06:45 AM
    MikeCrow
    Robert, Only sort of.
    Light enters the camera with a Poisson distribution, the photodetector converts the light into a voltage based on the ISO the camera is set to.
    In digital cameras, ISO is strictly amplification, the detector will get the same number of photons over x period of time. Photodetectors do have a specific conversion rate of photons to voltage, well size, thermal noise and signal noise. But some very smart people have figured out how to correct for most of this because it's all statistical in nature.
    Long exposure astrophotography (including the hubble) takes advantage of these traits.
    This is one of my favorite pictures, I collected about 45hours of exposure on a 80mm ~f/4-5 lens(telescope) with a Canon 40D digital SLR, this is the best ~18hr's.
    This is one of my favorite pictures, I collected about 45hours of exposure on a 80mm ~f/4-5 lens(telescope) with a Canon 40D digital SLR, this is the best ~18hr's.
    First, with most cameras you have to get them off the automatic settings (unless it has a nighttime mode, then that might work). Second you need to set the ISO as high as you can that doesn't introduce excessive signal noise, lastly get the camera's optical speed as fast (low) as possible. And try to get the exposure to be as long as possible. That should get you good pictures of the Moon, since it's very bright for an astro source.
    Since the Moon is so bright, you shouldn't have to actually do anything about noise, other than find the right settings on your camera(unless it has really slow optics, like a cell phone might have).
    To go deeper into space, you will generally need a german equatorial mount to track the sky, and a camera that has as a minimum a bulb control.
    If you have a good DSLR, The Canons seem to have had low noise sensors 10 or so years ago, and became the darling of the Astro crowd, and are still the camera of choice. Whether the other brands have caught up or not I don't know.
    Now back to you original concern about noise. You combat it by collecting 'lights' (multiple exposures of the subject), 'darks' (equal time exposures as the lights, but with the lens cap on), and 'bias' frames (as short as possible exposures with the lens cap on). Lights are the subject that get 'stacked'. Darks capture the thermal noise, which you stack to get a statistical map of the thermal noise. Bias frames get stacked and contain the non-thermal noise of the electronics. There's a free program called DeepSkyStacker that takes all of those subs, and turns them into pretty pictures.

    There's also a side branch that deals with planetary imaging, it uses (usually) webcam's, to take short exposures (for astro), then there's software to pick subs where the air is still, and stacks 100-1,000's of those. Some of these I've seen are amazing. There are also techniques for solar photography.
    I've gone after mostly Galaxies and Nebulas(Nebulae?).

    There's a good web site that has a lot of useful info, and a lot of people very willing to help.
    I've attached some other images on my dashboard too.
    —
    Never is a long time.
    Mi Cro | 03/02/12 | 10:14 AM
    Hank
    This is the most insightful 'applied' astrophotography primer I have ever read.  Now I want to run out tonight with my Rebel EOS and take some snaps.
    —
    Want more no-nonsense, independent science? Buy Science Left Behind
    Hank Campbell | 03/02/12 | 10:22 AM
    MikeCrow
    What EOS and lenses do you have? And do you have a tripod and bulb timer/switch?
    You can get 10-20 sec exposures before you get a lot of motion. And the Orion Nebula is bright enough to start getting something with a EOS.
    I just upgraded my 40D to a 7D, with the 40, I set ISO to 1600, 3200 didn't seem to be much of an improvement. With the 7 3200 might work.
    If you have something around a 200mm f-4/5 lens you can probably use autofocus, other wise you'll have to use manual focus.
    Then snap away. Download DeepSkyStacker and don't worry about noise, 10-20 seconds on an EOS won't have any significant noise unless the temps are probably well over 100.
    I can take 5 minute exposures when it's 20F and not have to take darks or bias frames.

    Oh, I did forget to mention flats. Flats are exposures of an equally lit flat surface. I use the sky. Flats generate a map of the optics flatness, dirt, vignetting, etc. DSS will use flats to remove optical aberrations. Just don't over expose your flats, that ruins them.

    Beyond this, you need a mount, and if it doesn't track good enough you need a guide scope setup, which you use on a bright star and set up a servo loop to keep your imaging camera pointed in the same spot. if you get dew in your area, you need lens heaters. And since battery life isn't so great an ac power supply if you have a plug close by. I run all of this in my driveway and have a computer in the garage that runs the guide scope and collects the subs so I don't run out of space on a flash drive.

    Lastly the darker the skys the better, a lot of people go to dark sites, and run off lead acid batteries. Because what you're trying to pull from the lights is the difference between the Poisson noise of the background sky, and the Poisson light of your target, the darker it is....................
    —
    Never is a long time.
    Mi Cro | 03/02/12 | 11:02 AM
    Hank
    I have a 55 and a 300 and a tripod but no bulb so I can get one of those. I'd definitely have to go into the hills to get any real darkness.
    —
    Want more no-nonsense, independent science? Buy Science Left Behind
    Hank Campbell | 03/02/12 | 11:26 AM
    MikeCrow
    The 300 should autofocus, that's useful all by itself.
    And you can use the timer until you get a bulb.
    —
    Never is a long time.
    Mi Cro | 03/02/12 | 11:36 AM
    rholley
    Setting the ISO manually does seem to make things better for my moon shots:


     
    Now I must also get round to setting colour temperature manually as well.  So far I’ve been relying on auto, and sometimes the camera seems to change its mind unpredictably, as with these two successive shots of plane tree bark:

    —
    Robert H. Olley Quondam Physics Department University of Reading England
    Robert H Olley | 03/05/12 | 17:42 PM
    Hank
    He recommended auto for my Rebel EOS but what is the fun in that??   Since the media are digital I am not wasting film and I can figure out the best way to do it manually and get a little smarter.
    —
    Want more no-nonsense, independent science? Buy Science Left Behind
    Hank Campbell | 03/05/12 | 18:54 PM
    MikeCrow
    Well there are a lot of advantages if it will autofocus. Does you camera have liveview?
    Without liveview manual focusing was really hard to do, and keep in focus.
    My telescope has a focus lock, but focusing on something you can barely see in the view window is difficult, and then as the temperature changes the tube changes length, altering focus. With a camera lens the focus ring seems to shift, plus the image is even smaller. Add a lens heater wrapped around it to keep dew away, well keeping a crisp focus while you take 40-60 5 minute subs, and autofocus is nice :)
    With liveview at 10x you can get a decent manual focus on something bright, then point it at stuff you can't even see to image.
    Almost all of the stuff I take pictures of I can't see before taking at least a 30sec exposure.
    One of my moon images(I don't shoot much stuff in the solar system).
    —
    Never is a long time.
    Mi Cro | 03/06/12 | 09:36 AM
    UvaE
    Nice pic, Robert. Typically the shadows on the dark edge capture the moon's texture. The sun's rays are not shining directly into the craters as when photographing a full moon.

    And Mi, I love the detail and those blue-green hues in your spectacular photo!
    Enrico Uva | 03/03/12 | 05:03 AM
    MikeCrow
    Enrico, One note. Eye's are a poor substitute for a sensor when looking at low light levels. Most of these object are at most fuzzy green blobs, until you get to very large apertures. The eye barely pickup up Orion even in a 8" f/10 scope. Normally to actually see galaxies and stuff you need to 20"+. It's only when you add long exposures that you get to 'see' the gems in space.
    —
    Never is a long time.
    Mi Cro | 03/02/12 | 12:50 PM
    UvaE
    Eyes are a poor substitute for a sensor when looking at low light levels.

    No argument there. Even using a 16' exposure with an inexpensive digital camera reveals many stars that the naked eye cannot see.

    But to come close to reproducing what we sense when looking at the night sky, the images cannot be projected on a flat screen or paper. You need a dome or planetarium.
    Enrico Uva | 03/03/12 | 04:54 AM