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Thread: CF-39 Issues

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    Sep 2015
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    CF-39 Issues

    Hi Everyone,

    I'm hoping the expertise here might be able to give me some guidance. I have recently acquired a Hasselblad CF-39 and I am using it on a Fuji GX680 and a Toyo VX126 currently. I am triggering it using flash sync, which seems to be working successfully so long as the shutter speed set on the back is the same or longer than the lens shutter speed on the Fuji or LF lens, e.g. no smearing or magenta casts. However, there seems to be an excess of colour noise in the shadows. I think I am seeing that this is worse when the shutter speed on the back is much longer than on the lens. The fastest shutter speed I can set on the back is 1/8 sec though, so if I am using 1/400 or 1/250 even through to 1/30 it is certainly very noticeable. When using longer shutter speeds it is easier to match them closely and the problem is less pronounced, though there is more colour noise present than I am used to seeing at base ISO with 35mm digital. Is this normal? My research suggested this sensor is the same as in the P45+ and although it is not implemented for long exposures in the same way, I still thought that the noise floor would be quite low. But it does seem like if the back is exposing without light then it produces a lot of noise.

    See attached image for a example. It is at 200%, which is excessive but the easiest way to make it obvious what I am talking about. It is still clearly visible at 100% but I feared web compression might change that. At 50% viewing the issue is not as apparent, but by that point I am at lower resolution that 24MP 35mm digital, which kind of undermines the point of having a 39MP back with no AA filter.

    I have also attached a second image showing what I assume are dead pixels, usually appearing as green or black spots. There seem to be a LOT of these.

    Comments/suggestions would be appreciated.

    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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ID:	114124   Click image for larger version. 

Name:	Dead pixels.jpg 
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