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Thread: blooming


  1. #1
    mpilting is offline Welcome Me!
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    Hello,

    I just purchased a Canon SX150 IS. I'm mainly going to be using it for scenery shots. Some of the photos I want to take are very high contrast (sunlight reflecting off water), and I'm concerned about possible blooming - photons crossing over into adjacent pixels. Other than anti-blooming gates, is there any way to mitigate this effect? Are there filters I could use that might help?

    Thanks,
    Matt


  2. #2
    Bishop is offline Dedicated Member
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    Not sure what blooming is... but you could invest in a polarizing filter for your lens, that will help.
    ~Linda~
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    Skippy is offline photozoholic
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    Are you asking about lens flare that shows up sometimes?


  4. #4
    mpilting is offline Welcome Me!
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    No, it's not lens flare. Blooming occurs when CCD chips become overwhelmed by too much light. Each well in a CCD chip can only hold so much charge, and once a well reaches its capacity, any extra charge leaks into neighboring wells, causing bright streaking and a washed-out look. Here's a vid on youtube demonstrating it:
    http://www.youtube.com/watch?v=-DoTgQbALU0

    Here's another example of CCD issues with bright reflections:
    http://www.youtube.com/watch?list=PL...endscreen&NR=1

    Personally, I would love to own a CMOS camera, since they tend to suffer from fewer aberrations and distortions, but a good CMOS camera would run into thousands of dollars, and I aint got that kind of cash.

    Bishop - It looks like you're right about the polarizing filter. I've been reading about it, and it appears polarizers can help clear up many exposure issues. Thanks for the tip!


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    JimL is offline Moderator photozoholic
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    A good polarizing filter, CP or CPL, depending on camera, will drop the exposure 2 stops otherwise change your angle to reduce the amount of light coming in the lens.

    Jim
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  6. #6
    mpilting is offline Welcome Me!
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    I'm happy to report that my new camera does not suffer from any of the aforementioned issues - at least not in still images. I photographed sunlight reflecting on water this morning, and all my images turned out great! I'm impressed! I haven't tested the video yet. When I do, I'll post an update.


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    chicagojohn is offline Mega-zoer
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    While lens flare can manifest as "blooming" apart from distinct hexagonal or octagonal light areas mimicking the leaves of the aperture (for which a hood can be helpful in preventing direct light rays from entering the lens), another thing to consider when photographing images of intrinsically high dynamic range is an HDR technique.

    The human eye and mind can process a bit depth of about 16 (from 0 to 65535 shadow to brightest), jpg and paper prints only handle a bit depth of 8 (0 to 255). The eye handles conditions of very bright sun to deep shadow by changing the size of the pupil and then letting the brain (mind and cognition) integrate the sense data to form a "perception".

    You can simulate that in HDR (high dynamic range) photography by taking a set of images that represent over-exposed to capture the detail in shadow to under-exposed to capture the detail in highlights, with images in between. Then software can stack these images in layers and select portions from each to use in creating a composite image, much like our cognitive-sensory system does when confronted with a HDR situation.

    For example, you might select a specific aperature, say f/8, and then take pictures from a tripod at exposures of 1/30, 1/60, 1/120, and 1/240 - increments of 1 EV apart in that each shutter speed allows exactly half the light of the former to register onto the sensor.

    These stacked images, then, could be processed by a program like Photomatix or the HDR software in Photoshop CS5 to produce, depending upon your choices, a composite interpretation.

    Sometimes we may labor under the illusion that we are "capturing" an image that is "out there". But it turns out that when you look into it, it isn't like that at all; either in photography or in what we think we see "out there" from seemingly its own side in the world.

    It turns out that the observer is a fundamental player in creating the observation in both cases. So there is nothing intrinsically impure in utilizing HDR methods, or any other, for that matter, in my view.

    ==========

    postscript....

    I was shooting an infrared image on the deck just now and the initial results reminded me of yet another potential source of "blooming". If you use the camera's capability of raising the mirror before activating the shutter, light coming from the viewfinder can find its way to the sensor creating a light patch there. If you are shooting the moon at night this isn't a problem, but it is in daylight. So you have to cover the viewfinder somehow to prevent light from entering it if you use a 2 second delay for instance.
    Last edited by chicagojohn; 06-02-2012 at 02:10 PM.
    "'There's more to a picture than meets the eye; hey, hey; my my." - Neil Young


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