http://imagej.273.s1.nabble.com/Tudor-DICOM-compressed-images-tp3693776p3693781.html
maximum displayed as the limits for the scaling down. So you either have
16 bit image directly. As long as both image are the same depth (8 or 16
Hugo A. M. Torres wrote:
> Hi Janne Hyötylä,
>
> This sounds reassuring!
>
> However, I've done a subtraction exercise and it seemed to affect the
> outcome: the resulting image was darkened all over (is this expected?)
> -- maybe I am doing it wrong: what I am trying to do is remove a couple
> of dark spots present in the lightpath picture from the specimen picture
> (darkspots are also present there).
>
> An important question that stems from this is whether I really should do
> a subtraction operation to accomplish what I want. Considering that
> darker pixels have lower values, should I be adding the pictures to one
> another instead? Either way, I did not get what I expected. Can anyone
> advise me on this?
>
> I was reading some imageJ documentation and it seems it might be
> important to calibrate the grayscale with a grayscale steptablet before
> doing the subtraction operation.
>
http://rsbweb.nih.gov/ij/docs/examples/calibration/index.html> Maybe thats the root cause of my problem?
>
> Here is what I did: 1 - convert the 16bit RGB to RGB, then to 8 bit,
> then process > image calculator and subtracted the blank file (lightpath
> background photo) from the specimen image file.
>
> Any help is welcome =]
>
>
>
> On Mon, 2009-02-09 at 15:26 +0100, "Janne Hyötylä" wrote:
>
>
>> On Mon, 09 Feb 2009 14:43:44 +0100, Hugo A. M. Torres
>> <
[hidden email]> wrote:
>>
>>
>>> Hello dear colleagues,
>>>
>>> ImageJ seems to be displaying some files incorrectly here. Please check
>>> this link:
http://imagebin.ca/view/6z_mf8hh.htmler>>>
>>> There I have the imageJ and another application (nautilus) displaying
>>> the same TIF file. The imageJ display seems more grainy and darker.
>>> The interesting thing is that it does not happen to every file! Specimen
>>> photos are displayed as expected.
>>>
>> Hello,
>>
>> ImageJ changes the value for white and and black according to the maximal
>> and minimal intensities in an image. This only affects how the image is
>> displayed, not the raw data itself. You can check this yourself by going
>> to Image > Adjust > Brightness/Contrast. You will see that in your case
>> the histogram does not go from 0 to 255 (or 0-65535 in 16bit) but a subset
>> of it. But when you change the sliders the raw intensity of each pixel
>> does not change. Any operation (subtraction etc.) will act on the raw
>> values so this will not be a problem.
>>
>> Nautilus on the other hand seems to fix black = 0 and white = 255 (or
>> 65535).
>>
>>
>> Best regards,
>> Janne
>>
>> --
>> Janne Hyötylä
>> Biozentrum / Swiss Nanoscience Institute
>> University of Basel
>>
>
>