Profondeur de champ en MICROphotographie
Pour ceux qui veulent dépasser la Macro (1 à 10X)et se consacrer un peu à la Microphotographie(au delà de 10X) l'objectif de microscope monté sur soufflet devient indispensable.
D'expérience je constate que l'objectif de base pour pratiquer cette technique et le plus prisé actuellement est un 10X qui,monté sur un soufflet vous permettra d'obtenir des grossissement de 10 à 15X et plus si le tirage de votre soufflet est assez long.
A ce niveau,j'avais peu de certitudes en ce qui concerne la PDC d'un cliché simple avec ce type d'optique et à ces rapports.J'ai donc posé la question à Rik Littlefield qui est une figure dans le domaine de la Microphotographie et entre autre le créateur du programme ZERENE STACKER!..
Sa réponse vient de tomber et je vous la livre telle quelle:
From: rjlittlefield To: Gérard-64 Posted: Tue Nov 29, 2011 9:09 am Subject: Re: DOF on Nikor 10X microscope objective http://www.photomacrography.net/foru...icon_quote.gif Gérard,
Quote: Could you tell me what is the DOF(in hundreds of millimeter) of this lens when used at his nominal distance(160mm)?
Short answer: 0.01 mm.
Long answer...
See Nikon MicroscopyU | Concepts and Formulas | Depth of Field/Focus and the interactive calculator at Nikon MicroscopyU | Interactive Java Tutorials | Depth of Field Calculator (requires a browser with Java).
In the calculator, choose an objective with the same magnification and NA that you have. The "CFI Plan Fluor DL 10X (0.30 NA)" would be a good choice. When it first comes up, the calculator probably shows depth of field 10.77 microns (0.01077 mm), corresponding to a value of 14 microns for "e". The parameter "e" has to do with sensor resolution. 14 microns is a reasonable value for "e", but then you want some overlap between slices , so maybe 70-80%% of 10.77 microns, call it 8 microns. Or you can just slide "e" clear to the left, where its value is 4, and get the calculator to say 7.44 microns. This latter is a quick and dirty technique that works pretty well.
Rounding 8 microns to the nearest hundredth of a millimeter gives the value I listed in the short answer, 0.01 mm = 10 microns. This will work well enough in practice. For some especially critical work with a troublesome subject you might prefer the 8 microns, but many subjects will look OK even at 15 microns.
Quote: And moreover :how to calculate the diminution of DOF when extending the below..?
Just use the formulas given by Nikon, with the same NA and the larger magnification.
I hope this finds you well. It sounds like you are having fun!
--Rik
Gérard-64 wrote: Hi Rik!
I would need your knowledge again:
At the moment I am using a Nikor Plan 10/0.30 C 160/0.17 microscope objective on a below.
Could you tell me what is the DOF(in hundreds of millimeter) of this lens when used at his nominal distance(160mm)?
And moreover :how to calculate the diminution of DOF when extending the below..?
Sorry to disturb you,I hope your are ok.
Best regards,
Gérard
J'espère que cela pourra aider certains d'entre vous et merci à Stéphane qui à soulevé le problème.
Un grand merci également à Rik Littlefield qui est un puits de science!
