Re: sCMOS salt'n'pepper issues

Posted by Christian Soeller on
URL: http://confocal-microscopy-list.275.s1.nabble.com/sCMOS-salt-n-pepper-issues-tp7583323p7583327.html

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Hi Neil,

We also have a Zyla 4.2 and I can mostly confirm Kyle's observation.

>
> Salt:
> In images with low signal and longer exposure times we see speckled
> bight pixels using both Volocity and ExCap/HDImage, with an intensity
> approx twice that of the background signal. Exposure times ~secs; low
> signal <1000 counts per pixel. These speckled hot spots were seen with
> all sCMOS cameras to some degree.
>
>
>

The salt (white pixels I presume) you see may be related to pixels with higher dark currents which may become troubling for long exposures. This makes those pixels not great for long exposures.

> Pepper:
> In almost the inverse situation, where we have higher signals with lower
> exposure times were also seen on all sCMOS cameras (the first camera
> with the clear hotspot had very bad 'peppering' compared to the others).
>
The pepper, presumably very dark appearing pixels, could be due to at least two things. (1) a local low gain (gain is in principle pixel dependent) and (2) high read noise.

A data post processing step is likely the best way to deal with some of these issues as are careful camera characterisation to guide that processing (see earlier reference to the Bewersdorf paper). Has anybody done this for confocal yet (rather than PALM/STORM)? In diffraction-limited imaging with suitable oversampling interpolation of missing data should be pretty doable.

Do the manufacturers offer any assistance with this? I would have thought they should if they market these cameras as an option in these systems.

Best,
Christian