How to convert pixels into squaremicrometer

[Sussi Rørdam Thomasen]

Hello everybody...
I am measuring fatcells for my masterproject, but I don't no how to convert the
area from pixels into squaremicrometer - the pictures that I have measured is
x20 magnification. Can anybody please help me?

Sussi Thomasen, Denmark

[Michael Schmid]

Hi Sussi,

you need the image scale in pixels per micrometer, e.g. by
taking a picture of an object with known dimensions.
Then, see the ImageJ documentation,
   http://rsb.info.nih.gov/ij/docs/menus/analyze.html#scale
or
   http://imagejdocu.tudor.lu/imagej-documentation-wiki/gui-commands/ 
set-scale

Michael
________________________________________________________________

On 3 May 2007, at 14:55, Sussi Rørdam Thomasen wrote:

> Hello everybody...
> I am measuring fatcells for my masterproject, but I don't no how to  
> convert the
> area from pixels into squaremicrometer - the pictures that I have  
> measured is
> x20 magnification. Can anybody please help me?
>
> Sussi Thomasen, Denmark

[Volker Baecker]

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Hello Sussi,
if you know the size of one ccd-element (from the description of the
camera) you can calculate the pixel size.

        pixel size = size of one ccd-element / magnification

Volker
Michael Schmid a écrit :

> Hi Sussi,
>
> you need the image scale in pixels per micrometer, e.g. by
> taking a picture of an object with known dimensions.
> Then, see the ImageJ documentation,
>   http://rsb.info.nih.gov/ij/docs/menus/analyze.html#scale
> or
>  
> http://imagejdocu.tudor.lu/imagej-documentation-wiki/gui-commands/set-scale
>
> Michael
> ________________________________________________________________
>
> On 3 May 2007, at 14:55, Sussi Rørdam Thomasen wrote:
>
>> Hello everybody...
>> I am measuring fatcells for my masterproject, but I don't no how to
>> convert the
>> area from pixels into squaremicrometer - the pictures that I have
>> measured is
>> x20 magnification. Can anybody please help me?
>>
>> Sussi Thomasen, Denmark
>
> --passerelle antivirus du campus CNRS de Montpellier
> --
>
>

... [show rest of quote]

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--

[Gabriel Landini]

On Thursday 03 May 2007 14:49:30 Volker Bäcker wrote:
> if you know the size of one ccd-element (from the description of the
> camera) you can calculate the pixel size.
>
> pixel size = size of one ccd-element / magnification

Remember to take into account for the magnification, any intermediate optics
in the extension tube that connects the camera and microscope (mine, for
example has a x0.5 lens in it).

It may be easier to measure a known distance of -let's say- micrometer
markings under the microscope and calculate the number of pixels, then divide
the real distance (in micromtres, etc) by the number of pixels and you will
have the pixel size. Then you put that value in the "set scale" dialog as
mentioned earlier.
However, this does not give you the resolving power of your setup. Many
objectives have less resolution than the pixel size you claculated. You
should consult the microscope manual for these values.

Many cameras sold for microscopy have smaller pixels than the resolving power
of the microscope objectives themselves, so caveat emptor!

Cheers,

Gabriel