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Thread: Several pictures to improve image resolution

  1. #21

    Default Re: Several pictures to improve image resolution

    Quote Originally Posted by slaam View Post
    on a side note
    i read b4 abt a method to reduce sensor noise of very noisy webcam photos
    first you take a few black photos to map the sensor noise then average it out and use this as a template to remove the noise from your pics..
    There are people using stacking software with a webcam for astro shots. Basically the video is captured ans the frames are stacked to give a still image, over time, the noise itself will average out leaving only the image. It's not uncommon to stack thousands of frames to give the image. http://www.astrostack.com/

    The problem with using black frame method is that the noise is dynamic and the noise for every frame is different, especially with CMOS sensors.
    Last edited by lsisaxon; 2nd March 2007 at 05:59 PM.

  2. #22

    Default Re: Several pictures to improve image resolution

    Quote Originally Posted by slaam View Post
    on a side note
    i read b4 abt a method to reduce sensor noise of very noisy webcam photos
    first you take a few black photos to map the sensor noise then average it out and use this as a template to remove the noise from your pics..
    If only it would be so easy...

    Noise is not constant, very dynamic and changing between shots, even if only seconds that differs between shots. That's why Olympus cameras take one extra black frame after each picture when noise reduction is activated.

  3. #23

    Default Re: Several pictures to improve image resolution

    But if nothing changes, then stacking the images will only serve to reduce noise or give you a better dynamic accuracy, but it will not give you a higher spatial resolution because the same object is still captured by the same pixels on the sensor, and that sensor will not give you the in-between information required to give you a higher resolution.
    Very small movements (caused by vibrations or air masses) can shift consecutive images in such a way that the same area of the object would be captured by the same pixel but not exactly in the same position. Thus, each pixel doesn't receive always de same image.
    That shifting could be smaller than one pixel diameter. (or not)
    All that could be used to predict the most probable value of new in-between pixels.

  4. #24

    Default Re: Several pictures to improve image resolution

    Quote Originally Posted by skanskan View Post
    Very small movements (caused by vibrations or air masses) can shift consecutive images in such a way that the same area of the object would be captured by the same pixel but not exactly in the same position. Thus, each pixel doesn't receive always de same image.
    That shifting could be smaller than one pixel diameter. (or not)
    All that could be used to predict the most probable value of new in-between pixels.
    Yes, provided you have sufficient information collected over many images to confirm that it's not noise. It is challenging in terms of processing. You will also have to predict how the objects have moved. If a study tripod is used on a relatively still object, there would theoretically not be any movement or the movement is too small to cross into the next pixel especially if a wideangle lens is used.

    In the case of astrophotography, what you said would be true because the magnification is very high, any slight movement is detectable.

    Perhaps those cameras with sensor-based image stabilizer can shift the sensor by 1/2 pixel on each axis and capture another image. This will give extra information. <- Unless someone/some company has already patented this before, now no one can patent this technique anymore because it is public information now.. Muhahahah!!
    Last edited by lsisaxon; 2nd March 2007 at 08:28 PM.

  5. #25

    Default Re: Several pictures to improve image resolution

    It's a shame because I've been designing several methods to get slightly different images. Anyway, patenting it it's expensive and difficult, and I'm almost sure somebody else uses this method.

  6. #26

    Default Re: Several pictures to improve image resolution

    actually, current sensor resolution is approaching the limits of lens design and in some cases some have argued that it has overtaken lens resolution...witness the discussions about how lens choice of among even the best lenses can seriously affect the image quality of images taken with a D2X or even the D200, cameras with very high pixel density...not to mention the even higher density in Olympus cameras...so I seriously doubt that there can be that much more resolution that can be found in stacking...as I expressed earlier, stacking would be useful for noise reduction but probably not that useful for upping resolution...very small movements, by air convection say, will probably not be very visible to lens resolution unless on a very hot day in a desert or immediately off a radiating object...

  7. #27
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    Default Re: Several pictures to improve image resolution

    Quote Originally Posted by skanskan View Post
    Hello.

    Does anybody know (*) how to improve image resolution using several pictures?

    Regards
    what u want to achieve, is commonly known as SuperResolution in the image processing field.

    it is still largely experimental though there are a few sample software/matlab codes. just google it. but mostly u will get IEEE papers on the subject.

  8. #28

    Default Re: Several pictures to improve image resolution

    Hi
    SuperResolution is exactly what I was looking for. I couldn't find it because I didn't know its name.
    I'm glad to see my ideas aren't just silly, though they aren't new.

  9. #29
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    Default Re: Several pictures to improve image resolution

    Quote Originally Posted by skanskan View Post
    Hi
    SuperResolution is exactly what I was looking for. I couldn't find it because I didn't know its name.
    I'm glad to see my ideas aren't just silly, though they aren't new.
    Your idea is not silly at all. though i'm surprised that SR is unheard of to many ppl here.

    anyway, just to note that there are also SR techniques that creates SR images using only a single photo with a large trained library or using perturbed information from its ownself. It is different from interpolation techniques. very experimental, so dont bother looking apps for it.

    If you are interested in implementation, pm me.
    Last edited by leews2001; 6th March 2007 at 11:12 AM.

  10. #30

    Default Re: Several pictures to improve image resolution

    There is another application of stacking, namely increasing DOF. See here for an explanation, discussions and links to software. I may try it one day.

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