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Thread: Spots on the sensor of Canon EOS.

  1. #1
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    Spots on the sensor of Canon EOS.

    ¶Hello
    ¶In practice current, of photographic catch of view all subjects, the camera does not comprise any visible defect,
    ¶I however made a test on the cleanliness of the sensor by aiming, with various openings, a clear bottom (a plain blue sky without apparent clouds) of F5.6 with F 22, the development being made on the infinite one.¶
    ¶Result:¶the sensor is perfectly clean.¶There is not aucuns defects.¶
    ¶Images (landscapes, portraits, macro etc…) do not comprise aucunes stains.¶

    ¶But I practise also the photograph through microscope.¶
    ¶There my images comprise very many microscopic points which sully the image.¶
    ¶That it occurs?¶

    ¶I took again the tests carried out previously.¶
    ¶I passed them in Photoshop in black and white and I asked for maximum contrast with a little stressing in order to have best possible visualization.¶
    ¶And there I saw appearing on the scale 1:1 of the catch of sight these tiny points.¶
    ¶Actually they are small circles hollowed out in the center, and perfectly rounds and of similar diameters.¶
    ¶Their dimensions remain same whatever the objective used.¶

    ¶Question:¶
    1.Which is their source (dimensions lower than 1 µm)
    2. Why appear they only on the photographs achieved by means of a microscope since it would seem that they belong to the matrix (sensor)?¶

    Cordially
    J-p Claes
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    Re: Spots on the sensor of Canon EOS.

    If you say 'dimensions lower than 1 µm', you would be comparing them to the scale in the image. On the sensor image, those spots would be a lot larger:
    your image field would cover about 15 µm (horizontal), your sensor would be something like 24 mm, that's >1000 x larger...

    Also, those spots don't have the aspect of sensor dust spots, which appear usually as (slightly) unfocused darker spots without rings around them, and
    are more apparent with smaller apertures (at F22 you will see them clearly) In addition, you see no spots on any picture other than microscope shots.

    That means that the sensor is clean

    Not knowing how you take your pictures through the microscope, I'll have to guess, but could the ocular be dusty, either the side towards the objective,
    or one of the internal surfaces? You change magnification by changing objectives, and use the same ocular all the time?

    Regards,

    Remco

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    Re: Spots on the sensor of Canon EOS.

    To know if the sensor is dusty, just take a peace of white paper, set your camera to F22 and make a picture of the white, don't worry about camarashake with the low shutterspeed.
    If you have dust on the sensor you will see it on the picture.
    In my opinion what you show seems something else.

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    Re: Spots on the sensor of Canon EOS.

    In microscope photography, most often an ocular is used as a relay lens, and most oculars or relay lenses have a condenser lens in their lower part. This condenser lens often is in focus or close to focused in the image on the sensor, and spots on the ocular condenser may appear in the image. If you thoroughly clean the ocular (relay lens), or defocus it by moving the camera to another distance from the ocular, maybe these spots change appearance.

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    Re: Spots on the sensor of Canon EOS.

    Hello with all,

    ¶And thank you for your answers.¶

    ¶I probably badly expressed myself.¶
    ¶"dust" as I show in image finds as well on the images of the sky as those seen through microscope.¶
    ¶They are with the same sites.¶
    ¶I deduce from it that they are on the sensor of the EOS.¶

    ¶Why they appear on the image made under the microscope?¶
    ¶And why do not appear it on a normal pulling even extremely increased on the image of the sky made in F22;¶ unless making a contrasted ultra image of it?¶

    ¶Carry out tests on a bottom of blank paper or a plain sky;¶and pass the image in Photoshop, ask on several occasions maximum contrast and you will see appearing defects which will astonish you?¶

    ¶Cordially
    ¶J-P Claes ¶

  6. #6

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    Re: Spots on the sensor of Canon EOS.

    Quote Originally Posted by toucan View Post
    "dust" as I show in image finds as well on the images of the sky as those seen through microscope.
    They are with the same sites.
    I deduce from it that they are on the sensor of the EOS.

    Why they appear on the image made under the microscope?

    ¶And why do not appear it on a normal pulling even extremely increased on the image of the sky made in F22;¶ unless making a contrasted ultra image of it?
    Probably, the image in the microscope has a virtual aperture, i.e. exit pupil of the objective that is much smaller than f/22 on a camera lens. Then, if there are objects on the AA filter of the camera, they will appear much sharper.

    These spots look like they may be liquid drops, as they have a more clear centre. However, they may also be diffraction artifacts originating somewhere else in the optical path. If you try the setup with another camera and get the same, it is the optical system, but if only this camera displays those spots, there is something in it, most likely staining on the AA filter.

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    Re: Spots on the sensor of Canon EOS.

    Hello Urban Domeij ¶

    Thank you for your comments.¶
    They seem to me completely plausible.¶
    I am able to almost make them all eliminate them with the software IRIS who makes Flat-field.¶
    Cordially ¶
    J-P Claes

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