[3DEM] number of required images

[Marin van Heel]

Dear Leandro,

For the derivation of the formula you may want to have a look at:

Marin van Heel and George Harauz, *Resolution criteria for three 
dimensional reconstructions*, /Optik/ *73* (1986) 119-122.

In that paper we also derived a formula for truly random orientations of 
projections which is more favourable than the Crowther's formula.

d  >= 2 * D / N due to the more favourable distribution of projection 
directions.

Hope this helps,

Marin van Heel

======================================

Leandro ESTROZI wrote:

> **** Messages to this list are automatically archived ***
> **** Please limit quoting of previous postings to the bare minimum ****
>
> Hi,
>
> Does anybody know from where the formula below is derived?
>
> N = pi * D / d
>
> where N is the number of required images in order to make a 
> reconstruction with diameter D at resolution d.
>
> Many people cite Crowther's Nature paper (1970) but that formula does 
> not appear therein.
>
> Thanks,
>
> Leandro.
>

-- 
================================================================

       Marin van Heel

       Professor of Structural Biology

       Imperial College London
       Department of Biological Sciences
       Biochemistry Building
       South Kensington Campus
       London SW7 2AY
       UK

       Tel:	   + 44 (0)20 7594 5316
       Fax:	   + 44 (0)20 7594 5317

       e_mail: m.vanheel at ic.ac.uk
       and:    Osnat Lipson <vanheel.office at ic.ac.uk>
       web:    www.cbem.ic.ac.uk


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