[3dem] dm3 vs dm4 format?

[Sigworth, Frederick]

I wrote DM3 and DM4 reader functions for Matlab. Formally the main difference in the file formats is that DM4 uses 64-bit integers instead of 32-bit integers to handle quantities such as file size and image size. I think DM3 won’t be able to handle files larger than 2 or 4 GB. 

The other difference, noted by Chris Boothroyd http://www.ntu.edu.sg/home/cbb/info/dmformat/index.html is that DM4 readers will have better forward compatibility, able to skip blocks they don’t recognize. There’s probably no reason not to use DM4 files.

Fred Sigworth


> On Apr 16, 2019, at 12:13 PM, Morgan, David Gene <dagmorga at indiana.edu> wrote:
> 
> Hi,
> 
>    One of our microscopes has a Gatan OneView camera.  Users keep switching back and forth between saving images in dm3 or dm4 format.  I would prefer to use one or the other, but I don't really know whether it matters which.  I know that the dm4 format metadata can easily deal with exposure times, number of frames, etc. and so I suspect it is a "better" format for this camera.  But that info may also be hidden in the dm3 metadata also, and if so, I'm sure I can parse it out.  Does anyone have comments or preferences?  Thanks.
> 
> --
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