Re: Contrast/brightness in selected areas

Posted by gankaku on Jun 27, 2014; 1:13pm
URL: http://imagej.273.s1.nabble.com/Contrast-brightness-in-selected-areas-tp5008461p5008469.html

Hi Soren, Hi Gabriel,

Thanks, Gabriel, for complementing my post.
I forgot to underline what you mentioned (and which is very important
here) that any intensity measurements after such a pseudo flat-field
correction are obviously extremely biased and cannot be considered reliable
nor accurate. So, in other words... they should rather not be performed!
But I assumed that Soren will not measure intensities on this image type
but rather improve visibility.

@ Soren: The link Gabriel provided actually gives you further understanding
also on the pseudo flat-field correction method included in my suggestion
and macro.

If somebody is also interested in the outcome of the macro/plugin here I
post a before-after-comparison snapshot


2014-06-27 14:39 GMT+02:00 Gabriel Landini <[hidden email]>:

> > > -----Original Message-----
> > > I have a TEM picture which is composed from 4 collectors and merged
> > > automatically into one picture. However, the setup is not calibrated
> > > properly, leading to different contrast/brightness for the different
> > > collectors. Therefore I am trying to go through the four sub pictures
> one
> > > by one and adjust the contrast so that I get a nice final picture
>
> Further to the good previous advice, the problem is that your background is
> not even, so just adjusting brightness to 2 adjacent frames probably does
> not
> make the other adjacent frames match.
> One thing you can do is to convert your montage to a stack as suggested,
> then
> try to 'flatten' the background of your images using some background
> correction method and remake the montage.
>
> You should read this (the "retrospective" section):
>
> http://imagejdocu.tudor.lu/doku.php?id=howto:working:how_to_correct_background_illumination_in_brightfield_microscopy
>
> then try some of the "a posteriori" methods, but always having in mind that
> will be degrading the image contents by making assumptions on how the
> background behaves, when we do not know how correct that is. The images
> might
> look better, but the image data might become artificially biased (eg, if
> you
> are intending to measure intensities).
>
> Good luck,
>
> Gabriel
>
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>

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