Setting Min and Max vs Brightness

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Setting Min and Max vs Brightness

Chris O'Connell
This post was updated on .
I'm having trouble articulating the difference between these options.  I
understand what Min and Max do when setting B&C, but the description in the
user guide for "Brightness" is not clear to me what it's doing to the
distribution of intensities.  Is it correct to say that setting the Min and
Max will define the display white and black intensties of the image, while
Brightness shifts the entire distribution of pixel values toward one or the
other?  

Also, I've always used only the Min and Max adjustments to stretch the
histogram.  Is there a reason why one would not want to use Brightness for display adjustment?

Chris



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Re: Setting Min and Max vs Brightness

Michael Schmid-3
Hi Chris,

yes, Min & Max set the pixel value where the display intensity becomes
saturated black & white. I guess that it is used most often, and it
directly relates to the histogram (you see roughly how many pixels are
saturated black or white).

Contrast keeps the mid-gray value, but increases/decreases the slope
(the contrast, as the name says). Reducing contrast is also a way to get
the min and max values beyond the full range, which can be required in
some special cases (then no pixels reach saturation).

Brightness shifts the whole range (Min and Max are shifted by the same
amount). Adjusting brightness is very valuable in some cases.
E.g., I have scanning probe images where the height is encoded as
brightness. If I have several terraces with weak height variations (weak
contrast) on each terrace, I set the min-max range to encompass only one
terrace, and I shift the brightness to see the other terraces with the
same contrast.


Michael
________________________________________________________________
On 09.01.19 19:02, Chris O'Connell wrote:

> I'm having trouble articulating the difference between these options.  I
> understand what Min and Max do when setting B&C, but the description in the
> user guide for "Brightness" is not clear to me what it's doing to the
> distribution of intensities.  Is it correct to say that setting the Min and
> Max will define the display white and black intensties of the image, while
> Brightness shifts the entire distribution of pixel values toward one or the
> other?
>
> Also, I've always used only the Min and Max adjustments to stretch the
> histogram.  Is there a reason why one would not want to use Brightness and
> Contrast for display adjustment?
>
> Chris
>

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Re: Setting Min and Max vs Brightness

Chris O'Connell
This post was updated on .
Thanks Michael.  That explanation helps.  It finally occurred to be that
increasing brightness doesn't increase the dynamic range of the displayed
image, which is usually my main goal for presentation. That's the key point
and the reason to stretch the histogram using the min and max sliders. Your
conditions where B&C adjustments are useful are worth keeping in mind.

Chris



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