calculate magnification

[xlancelot]

Hi everybody,

i would like to calculate the magnification of my image

i took an image of a mark with actual size 3 mm using my webcam

image resolution is 1600x1200 and the webcam is using 2 MP cmos sensor  

now how can i calculate the magnification between the mark real size and the mark shown form the image ?

sorry for my bad english

thank you

[John Oreopoulos]

xlancelot,

You need to know actual physical size of your camera's chip sensor pixels (probably on the order of micrometers) to do this calculation. You can probably look this up in the specification sheet for your camera on the manufacturer's website. Then you can see how big the marks measure on your camera and compare this to the known size of 3 mm.

John Oreopoulos
Staff Scientist
Spectral Applied Research Inc.
A Division of Andor Technology
Richmond Hill, Ontario
Canada
www.spectral.ca



On 2014-02-10, at 11:39 AM, xlancelot wrote:

> Hi everybody,
>
> i would like to calculate the magnification of my image
>
> i took an image of a mark with actual size 3 mm using my webcam
>
> image resolution is 1600x1200 and the webcam is using 2 MP cmos sensor  
>
> now how can i calculate the magnification between the mark real size and the
> mark shown form the image ?
>
> sorry for my bad english
>
> thank you
>
>
>
> --
> View this message in context: http://imagej.1557.x6.nabble.com/calculate-magnification-tp5006474.html
> Sent from the ImageJ mailing list archive at Nabble.com.
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html

--
ImageJ mailing list: http://imagej.nih.gov/ij/list.html

[xlancelot]

i had tried to search on manufacturer's website about the cmos sensor pixel size
and i didint find any informations about it, but i found a smiliar 2 MP cmos sensor data sheet from other company let's use it , it said the pixel size 2.2 micrometer x 2.2 micrometer
so what should i do to calculate the magnification ?

[Glen MacDonald-2]

Open the image in Fiji and disable any spatial calibration (Analyze>Set Scale).  draw a line across the 3 mm object with the straight line tool.  You have 2 options- Measure the length (Analyze>Set Measurements>Perimeter [gives length on straight lines])  and divide # pixels/3 mm for pixels/mm; or go back to Set Scale and enter the known distance.  This can be set for future images through Image> Properies…  
Note that saving files as jpeg or tiff will often throw away the spatial calibration.  Another option for measuring the diameter is to download the FWHM macro.  
For more info, Help>ImageJ Documentation
Glen
Glen MacDonald
        Core for Communication Research
Virginia Merrill Bloedel Hearing Research Center
        Cellular Morphology Core
Center on Human Development and Disability
Box 357923
University of Washington
Seattle, WA 98195-7923  USA
[phone]
[hidden email]







On Feb 10, 2014, at 8:39 AM, xlancelot <[hidden email]> wrote:

> Hi everybody,
>
> i would like to calculate the magnification of my image
>
> i took an image of a mark with actual size 3 mm using my webcam
>
> image resolution is 1600x1200 and the webcam is using 2 MP cmos sensor  
>
> now how can i calculate the magnification between the mark real size and the
> mark shown form the image ?
>
> sorry for my bad english
>
> thank you
>
>
>
> --
> View this message in context: http://imagej.1557.x6.nabble.com/calculate-magnification-tp5006474.html
> Sent from the ImageJ mailing list archive at Nabble.com.
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html

--
ImageJ mailing list: http://imagej.nih.gov/ij/list.html

[Divakar Ramachandran-2]

On Tuesday 11 February 2014 06:47 AM, Glen MacDonald wrote:
> Open the image in Fiji and disable any spatial calibration (Analyze>Set Scale).  draw a line across the 3 mm object with the straight line tool.  You have 2 options- Measure the length (Analyze>Set Measurements>Perimeter [gives length on straight lines])  and divide # pixels/3 mm for pixels/mm; or go back to Set Scale and enter the known distance.  This can be set for future images through Image> Properies…  
> Note that saving files as jpeg or tiff will often throw away the spatial calibration.  
In my experience, saving as TIFF preserves scale information, though
only for reading through ImageJ.

Divakar

> Another option for measuring the diameter is to download the FWHM macro.  
> For more info, Help>ImageJ Documentation
> Glen
> Glen MacDonald
> Core for Communication Research
> Virginia Merrill Bloedel Hearing Research Center
> Cellular Morphology Core
> Center on Human Development and Disability
> Box 357923
> University of Washington
> Seattle, WA 98195-7923  USA
> [phone]
> [hidden email]
>
>
>
>
>
>
>
> On Feb 10, 2014, at 8:39 AM, xlancelot <[hidden email]> wrote:
>
>> Hi everybody,
>>
>> i would like to calculate the magnification of my image
>>
>> i took an image of a mark with actual size 3 mm using my webcam
>>
>> image resolution is 1600x1200 and the webcam is using 2 MP cmos sensor  
>>
>> now how can i calculate the magnification between the mark real size and the
>> mark shown form the image ?
>>
>> sorry for my bad english
>>
>> thank you
>>
>>
>>
>> --
>> View this message in context: http://imagej.1557.x6.nabble.com/calculate-magnification-tp5006474.html
>> Sent from the ImageJ mailing list archive at Nabble.com.
>>
>> --
>> ImageJ mailing list: http://imagej.nih.gov/ij/list.html
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html

--
ImageJ mailing list: http://imagej.nih.gov/ij/list.html

[tamasflex]

More concretely.
What webcam use, see image on the screen or on the picture ...
There are many ways to calculate the magnification.
Send some pictures on your device.

Some links:

http://t7.hu/00h9
http://t7.hu/00hb
http://t7.hu/00hg
http://t7.hu/00hi
http://t7.hu/00hj
http://t7.hu/00hl