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Thread: Dust Sensor Check

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    Dust Sensor Check

    Hello!

    I own a CVF Back and noticed a lot of small spots after long exposure shooting in cold nights in Montreal (-20c)...

    this is certainly no matter with cold but the long exposures on skies is showing obvious dark spots.

    I removed my lenses and the spots seems hard to read (extremely blurry) when I take a picture without lens,
    how come the dust located on the sensor itself would be showing sharper with Lens ? normally, the dust should look exactly the same without lens if its located on the filter ? am I wrong ?

    My other concern is that Dust is located exactly at the same spots even with different Lenses, 80mmor 150mm, and obviously sharper and crispier at f22...

    do you think the Dust is behing the IR filter? I cleaned the surface gently but its still there...


    thanks a lot for your advice.

    El Rafo

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    Re: Dust Sensor Check

    Without a lens to refract the light on the sensor the dust spots will be very blurred. And with a lens on as you increase the aperture to say f16 or higher they will get more defined.

    More than likely you need to do a wet clean of the sensor.

    Might want to check with the camera company to see what solution they recommend. You should be finite with eclipse and pec pads. You will need a blade to wrap the pad around.

    If you are in the US both Digital transitions and Capture Integration sell cleaning kits that will have everything you need.

    Paul C

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    Re: Dust Sensor Check

    Thanks Paul.

    I went to my Pro Camera Shop in Montreal and we cleaned the IRfilter, with wipe and friction alcohol,
    Now, the filter is very clean but I still see dust spots on my pictures, I guess they are under the filter, on the Sensor...

    is Only Hasselblad able to clean the sensors ? is there a way to get rid of dust under IR filter ?

    Thanks

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    Subscriber & Workshop Member GrahamWelland's Avatar
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    Re: Dust Sensor Check

    I would be very surprised if the dust is below the IR filter unless it's been removed at some point, although obviously it IS possible. The only way that you could get that cleaned would be to send it in to Hasselblad as far as I know. Given your description of long exposure on cold nights I'd be more inclined to think that you have persistent spots on the IR glass from condensation & evaporation vs dust.

    You might want to have a chat with one of the techs at your local MF dealers such as B3K or Visitec?

    I use a sensor loupe from Visible Dust to check my sensor for dust that is hard to see. It has a light that projects and you can easily see any dust at an oblique angle. It could be also that you need a proper detergent clean if you have spots on the sensor from condensation after the cold nights - I don't know what Hasselblad recommend but with Phase One backs there are two cleaning solutions - the normal evaporative clear solution that you probably used at your dealer, and also a blue detergent solution that is used for deep cleans (that I suspect most of us have never had to use btw).
    Remember: adventure before dementia!

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    Re: Dust Sensor Check

    If it's under the IR then it will have be cleaned by the camera company or authorized service center.

    Paul C

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    Re: Dust Sensor Check

    Please post a photo.

    As they say a picture is worth a 1000 words.

    It's possible the issue isn't what you think it is. But very hard to tell from your description.
    Doug Peterson , Digital Transitions | Email
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    Re: Dust Sensor Check

    If cleaning is too expensive or you just can't figure out what it is, you could always shoot a a blank image which would only show your spots. Then use that for LCC file and could be subtracted from all your images.

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    Workshop Member Wayne Fox's Avatar
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    Re: Dust Sensor Check

    Quote Originally Posted by elrafo View Post
    Thanks Paul.

    I went to my Pro Camera Shop in Montreal and we cleaned the IRfilter, with wipe and friction alcohol,
    Now, the filter is very clean but I still see dust spots on my pictures, I guess they are under the filter, on the Sensor...
    is Only Hasselblad able to clean the sensors ? is there a way to get rid of dust under IR filter ?

    Thanks
    is this where you bought the back? I would be very surprised if dust is between the filter and the sensor. Just because they “cleaned” it doesn’t mean it is clean. When you say “wipe” and “friction” alcohol, not really sure what you mean. There are some pretty bad “wipes” and cleaning solutions out there that are designed for lenses, not sensors.

    With a digital back and some high power reading glasses you should be able to shine a little bright flashlight at a very oblique angle and see the spots on the surface of the glass. I don’t even shoot to test if my back is clean, pretty easy to see if I missed anything, and whether a rocket blower is enough to get it off. Doing this it would be pretty easy to see if they were on top or sitting underneath the IR filter
    Last edited by Wayne Fox; 3rd March 2014 at 00:10.
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    Re: Dust Sensor Check

    thanks all,

    I will send you some sample photos, I will do a check of my sensor with a strong light too as you recommand.

    Can a Local camera repair shop clean my sensor and open the IR Filter or that is too risky ?

    is there a "air void" between IR and Sensor ?

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    Re: Dust Sensor Check

    ok I have checked with a light...
    this is not good, its right under the surface of the filter, not on the sensor but on the other side of the glass!
    they look like super small bubbles, white dots...

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    Re: Dust Sensor Check

    Hello There!

    could a Shutter Blade (damaged) do this kind of permanent spots to a IR Filter ?

    Hasselblad US want me to replace my shutter blades, I didn't ask for any repair on my body btw but I sent it with the back...

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    Re: Dust Sensor Check

    Just FYI the best way to find dust spots is to shoot a plain wall at say f16 and a longish exposure and pan the camera during the exposure, this will blur out everything but the spots, can be scary!
    You could then use the dust removal tool in Phocus and create a preset that would would as long as the dust stays put.

    Nick-T

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