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Thread: Canon LF sensor

  1. #21

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    Re: Canon LF sensor

    Ok, what are the f stops for a reflector telescope this would typically be fitted to? I'm serious, are these calculated similar to refractor lenses?
    Expert in non-working solutions.

  2. #22

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    Re: Canon LF sensor

    Quote Originally Posted by Havoc View Post
    Ok, what are the f stops for a reflector telescope this would typically be fitted to? I'm serious, are these calculated similar to refractor lenses?
    I'd say that in a reflector the primary mirror diameter is taken to calculate the aperture, the rest should be the same.

    Sky explorers like to speak in arc terms, but here you have it well explained: https://www.astronomy-electronics-ce...lvingpower.htm

  3. #23
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    Re: Canon LF sensor

    Quote Originally Posted by Pere Casals View Post
    But it would not be necessary to use a lens that outresolves the sensor. A Nikon D3400 also has usually much more pixels than the popular lenses are able to resolve...
    For once I heartily agree with Pere Casals! A photographer or videographer would use a lens that allows them to makes the photos in the style they want.

  4. #24

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    Re: Canon LF sensor

    Quote Originally Posted by Eric Woodbury View Post
    Lenses are limited in their ability to focus a point. It's called the diffraction limit. The faster the lens, the smaller the spot you can focus. The sensor in question here has 2 micron pixels. To get an infinitely small spot to focus into a pixel that size with green light (at least most of it, first null of the Airy disk), requires this insane f-number. There are some ways to get around this problem, but not practical for normal humans.

    BTW, they still fly film in U-2s. Film is good stuff at a bargain price (relatively speaking).
    The description for the large sensor does not say anything about pixel size. The 2.2 micron pixel size is mentioned in the 120 MB sensor, which is quite small (APS). If the large sensor (400 cm^2) had 2.2 micron pixels, there would be over 8 thousand megapixels. Even if it isn't color, the data coming out of it would take a very long time to get into a laptop or other storage devise

    So the calculations for a suitable lens that follow are likely based on a too-small pixel size. Pixels could be > 10 microns, to be sensitive enough to the very low light levels.

    Maybe someday, there will be 400 cm^2 digital sensor with 2-micron pixels that have low noise and are not prone to saturation, but save your egg money and pass on this one -- it is a very poor fit for normal large format photography.

  5. #25

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    Re: Canon LF sensor

    Quote Originally Posted by mmerig View Post
    The description for the large sensor does not say anything about pixel size. The 2.2 micron pixel size is mentioned in the 120 MB sensor
    ... yes, but the article says that this sensor will be employed an astronomical Schmidt camera (https://en.wikipedia.org/wiki/Schmidt_camera).

    In this kind of projects pixel size should be matched to the resolving power of the optical intrument.

  6. #26

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    Re: Canon LF sensor

    Quote Originally Posted by Pere Casals View Post
    ... yes, but the article says that this sensor will be employed an astronomical Schmidt camera (https://en.wikipedia.org/wiki/Schmidt_camera).

    In this kind of projects pixel size should be matched to the resolving power of the optical intrument.
    Maybe the pixel size is matched to the resolving power, maybe not. One thing the sensor may not be matched to is the curved focal plane that normal Schmidt cameras typically have, although the one they are using probably has a field flattener. But the flatteners can degrade resolution.

    The Canon articles are apparently for marketing, and without much more information, how well the sensors would work is open to a lot of speculation; I am not going to speculate any further.

  7. #27

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    Re: Canon LF sensor

    Quote Originally Posted by mmerig View Post
    Maybe the pixel size is matched to the resolving power, maybe not.

    how well the sensors would work is open to a lot of speculation; I am not going to speculate any further.
    You are right, we are speculating, we only know that the other CCDs used in the Kiso observatory are 24um and 17um, refrigerated and having low dark current levels. Other sensors in the VLT are 10um...

    ...Canon will make the pixel size that customers will find most useful...

    I guess that Canon is presenting a new product line that is primarily targeted to astronomical applications, where the common choice is joining MF sensors in a mosaic when wanting to obtain really big sensors.

    I guess that a composite sensor should need 2 exposures per image, being the second image a bit shifted, to fill the separations between sensors, perhaps they shift the sensor rather than moving the telescope. This way allows making monster sensors from industrially available components.

    Of course that cannon development would simplify sensor developments and operation of telescopes not requiring monster sensors like the one in the Gaia.

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