[3dem] RE: mrc format

[michael]

Dear Anchi,

First of all: sorry for my very delayed answer.

I am not working with MRC files but when updating the EM2EM program I 
noticed the two incompatible definitions of your and Roberto's mail. To 
be honest I do not mind how the MRC header is defined as long as there 
is  a definition how MX/MY/MZ and NZ/NY/NZ should be set / should be 
read in case of a single 2D image or 3D volume and in case of a stack of 
2D images or 3D volumes.

I was playing a bit devil's advocate knowing that my "proposal" does not 
fit the CCP4 meaning of MX/MX/MZ (thank you for the nice illustration). 
Nevertheless, seen from an image processor's point of view I am still a 
bit confused that NZ can be both, the number images in a 2D stack and 
the number of sections in a 3D volume. Assuming that every 2D image is 
also a 3D volume with one section only I would set NZ=1 for 2D images 
(single or stacked) and never use NZ as the number of 2D images in a stack.

Well, we cannot change this any more because all programs meanwhile use 
NZ = total number of 2D images/sections. So I think that your definition 
is correct: MX/MY/MZ are defining the unit cell (the size of a single 
"object") and NZ is the total number of 2D images/sections. The only 
problem is that most of the 3DEM (including many MRC) programs mostly 
set MX=MY=MZ = 0 .

Thank you for your explication and help! Please let me know if a final 
MRC/CCP4 decision is made.

Best regards
Michael


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