[3dem] 3dem Digest, Vol 145, Issue 24

[Anchi Cheng]

Tim,

Check exactly what format it came as.  If the intensity scales o.k. (i.e.
the negative values are not a saturated pixel value got wrapped to negative
values), most likely that the format (say unsigned 32-bit is the original format)
is now being read as signed 32-bit.

Anchi

> Message: 1
> Date: Mon, 16 Sep 2019 22:13:50 +0200
> From: Tim Gruene <tim.gruene at univie.ac.at>
> To: 3DEM List <3dem at ncmir.ucsd.edu>
> Subject: [3dem] diffraction data: negative counts on OneView Cammera
> Message-ID: <1696621.bkbEN96OPT at hilbert>
> Content-Type: text/plain; charset="us-ascii"
> 
> Dear all,
> 
> I received some diffraction data sets collected with a Gatan OneView detector 
> in binning mode (512x512 pixels). The images contain many negative counts, at 
> least according to Fiji and to Matlab. Would anyone have an explanation for 
> this?
> 
> I did ask for as raw as possible data. Without flatfield/darkfield correction, 
> however, I would still not expect negative counts.
> 
> The data are 32-bit. Since there are negative counts along the beam stop, I 
> would also rule out misinterpretation of the data as signed instead of 
> unsigned.
> 
> I would appreciate some ideas, as to how a camera could produce negative 
> counts. 
> 
> Best regards,
> Tim
> 
> -- 
> --
> Tim Gruene
> Head of the Centre for X-ray Structure Analysis
> Faculty of Chemistry
> University of Vienna
> 
> Phone: +43-1-4277-70202
> 
> End of 3dem Digest, Vol 145, Issue 24
> *************************************