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Dear Leandro,<br>
<br>
For the derivation of the formula you may want to have a look at:<br>
<span style="font-size: 12pt;"><br>
Marin van Heel and George Harauz, <b style="">Resolution
criteria for three dimensional reconstructions</b>, <i style="">Optik</i>
<b style="">73</b> (1986) 119-122.<o:p></o:p></span>
<br>
<br>
In that paper we also derived a formula for truly random orientations
of projections which is more favourable than the Crowther's formula.<br>
<br>
d >= 2 * D / N
due to the more favourable distribution of projection directions.<br>
<br>
Hope this helps,<br>
<br>
Marin van Heel<br>
<br>
======================================<br>
<br>
Leandro ESTROZI wrote:
<blockquote cite="mid440714E1.6030808@ibs.fr" type="cite">**** Messages
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<br>
<br>
Hi,
<br>
<br>
Does anybody know from where the formula below is derived?
<br>
<br>
N = pi * D / d
<br>
<br>
where N is the number of required images in order to make a
reconstruction with diameter D at resolution d.
<br>
<br>
Many people cite Crowther's Nature paper (1970) but that formula does
not appear therein.
<br>
<br>
Thanks,
<br>
<br>
Leandro.
<br>
<br>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
================================================================
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: <a class="moz-txt-link-abbreviated" href="mailto:m.vanheel@ic.ac.uk">m.vanheel@ic.ac.uk</a>
and: Osnat Lipson <a class="moz-txt-link-rfc2396E" href="mailto:vanheel.office@ic.ac.uk"><vanheel.office@ic.ac.uk></a>
web: <a class="moz-txt-link-abbreviated" href="http://www.cbem.ic.ac.uk">www.cbem.ic.ac.uk</a>
</pre>
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