32 bit is definitely a waste of space. 



If you are using a K2 in counting mode, then obviously keeping more bits than the maximum number of counts you can get in one frame is pointless. This is why there is a 4-bit variant of the MRC format (unfortunately unofficial, but SerialEM will use it in some cases). Yes, many people are actively collecting movie data with only 4 bits per pixel.



Now, if you're using integrating mode, things become a bit more complicated. Even if what you want in the end is the same "number of counts" you get from the counting mode detector, this signal is buried in point-spread, etc, and if you keep too few bits, you will lose some information. Bottom line is that you need more bits for this than for counting mode, but probably not too many more. For movie-mode imaging, where the e-/pixel/frame is low, there is little point in keeping a lot of bits. 



I think Fred Sigworth did some formal estimates recently... I think even in integrating mode, for movie frames, 8 bits is more than sufficient. 





> On Mar 9, 2016, at 11:01 AM, Edoardo D'Imprima <[log in to unmask]> wrote:

> 

> Dear all,

> 

> I have a general question about cryo-data collection with direct detectors: does it make any difference in terms of high resolution image processing to collect movies in 16 bit vs 32 bit? In principle one can save quite a lot of storage space but I’m not so sure that this procedure will be harmless. Are the high resolution components somehow damaged during the normalisation or particle alignment? 

> 

> Is there any experience regarding this topic? 

> 

> Any suggestion will be very appreciated, many thanks in advance.

> 

> Edoardo

> ---------------------------------------------------

> Edoardo D'Imprima

> PhD Student

> Max Planck Institute of Biophysics

> Structural Biology Department

> Max-von-Laue Straße 3

> 60438 Frankfurt am Main

> Germany

> 

> Tel: +49 (0) 69 6303 3015