Re: resolution affect intensity?

Posted by Ben Tupper on Dec 08, 2008; 2:15pm
URL: http://imagej.273.s1.nabble.com/resolution-affect-intensity-tp3694298p3694299.html

On Dec 8, 2008, at 7:56 AM, shilo2 wrote:

> Dear list members
> Maybe it’s a stupid question but because I'm a beginner I must ask
> In a mistake I took some pictures (confocal microscope) in low  
> resolution
> (256*256). The majority are in more high resolution (512*512). Now,  
> I would
> like to compare intensity's.
> Does the resolution should affect the intensity means? If the  
> answer is yes
> , is there a way to correct it?
>

Hi,

That doesn't seem like a stupid question to me.  I assume you mean  
greyscale intensity - in which case your best way to make the  
comparison is to "normalize" the integrated density by area.  This  
gives you the mean grey value which is one of ImageJ's measurement  
selections (see http://rsb.info.nih.gov/ij/docs/menus/analyze.html#set).

normalized grayness = mean grey value = (integrated density) / area

Once normalized, you can reasonably compare across different  
resolutions.*
Hope that helps.

Cheers,
Ben

* There are other issues involved, including how the pixel binning  
was done between the low and high resolution.  If you need to dig  
into that you'll have to consult your camera documentation and an  
image processing reference. This one (http://www.imagingbook.com/) is  
a goodie.