Hi John
And while we have you as a captive audience at the other side of the room, have you considered using shared backgrounds for complex situations for mapping? At the moment we can use either MAN or off-peak.......
Cheers
Malc.
Shared backgrounds in calcimage would be really useful, because it would minimize the number of off peak maps to be measured. In PfE I use for 6 elements on the same spec the same 2 high and 2 low backgrounds with an exponential fit (sharing the backgrounds and then multiple point backgrounds, I skip the acquisition of all the other backgrounds using the Nth point feature). In CI, I would have to acquire 12 background maps instead of only 4. I will now trick the system and take the average of the 2 high and 2 low background maps, respectively, and apply them to all 6 elements. But it seems the only way. The acquisition of this 500 x 3000 pixel map took several weeks, so I am going to use it, whatever the cost. ![Smiley :)](https://probesoftware.com/smf/Smileys/default/smiley.gif)
Your wish is granted!
![Smiley :)](https://probesoftware.com/smf/Smileys/default/smiley.gif)
This wasn't easy to implement but I think we have something that will work.
Some history first: when we first designed Probe Image (for map acquisition) and CalcImage (for quantification of maps) we knew that we would need to support both off-peak and MAN background methods, but we never imagined that anyone would ask for a multi-point background (MPB) method for mapping:
https://probesoftware.com/smf/index.php?topic=701.msg4283#msg4283That means that in Probe Image one can decide whether to acquire both high and low off-peaks, no off-peaks (when using the MAN background method), or just one either high or low off-peak (for the high only, slope-high, low only or slope-low off-peak background fit models).
Now to be clear there are two different versions of multi-point backgrounds. First there is the original MPB method where the user specifies multiple (two or more, usually 4 or so) background positions for each analyzed element as originally suggested by a number of people: Mike Jercinovic, Julien Allaz, Mike Williams and Philipp Poeml. Later we implemented a "shared" off-peak method as suggested by Karsten Goemann:
https://probesoftware.com/smf/index.php?topic=9.msg1579#msg1579This "shared" off-peak method is based on two off-peak point backgrounds per element, *but* where at least two elements share the same spectrometer and crystal. The idea being to convert these multiple off-peak backgrounds into multi-point backgrounds so that they can be used by all the elements on that spectrometer/crystal. Of course we want to avoid interpolating (or extrapolating) across absorption edges, but this method turns out to be very useful for situations where the background is curved and one doesn't want to bother acquiring MPBs in the first place.
A discussion comparing the advantages and disadvantages of these various background methods is here:
https://probesoftware.com/smf/index.php?topic=1378.msg9999#msg9999However, since the MPB method is really a trace element method, we never imagined that we would get requests for an MPB mapping method in CalcImage. In any case, we decided to not implement the option to acquire multi-point background maps in Probe Image and that decision seems to have worked out well for the purposes of this new capability in CalcImage in order to quantify X-ray maps using (shared) multi-point backgrounds, because it does make sense for the "shared" MPB method, since one merely utilizes the off-peak map acquisition options selected in Probe Image.
Starting with v. 13.8.5 of the latest Probe for EPMA software release one can now acquire off-peak maps in Probe Image, and if the "shared" background method is specified in Probe for EPMA for the sample basis in CalcImage (by using the Search for Shared Backgrounds button in the Analyze! window as shown here):
![](https://probesoftware.com/smf/gallery/1_13_06_24_12_47_21.png)
one can apply a (shared) MPB method to their x-ray map quantifications! How cool is that?
![Cool 8)](https://probesoftware.com/smf/Smileys/default/cool.gif)
Please note that there is one important difference between the MPB method in Probe for EPMA and how the MPB method is applied in CalcImage: in Probe for EPMA, when the user specifies the fitting parameters that the (shared) MPB off-peak method utilizes (by using the Iterate To parameter or the manual "Always Use" or "Never Use" manual flags), one can be assured that a non-zero intensity will be found because Probe for EPMA always acquires all off-peak points that are specified for the sample.
However, because in Probe Image one can specify to either acquire both off-peak maps, one off-peak map or no off-peak maps, CalcImage cannot be assured that all off-peak maps are available.
Therefore CalcImage will, if it cannot find a specified off-peak map, set the manual flag for that point (actually pixel), as "Never Use", so a zero intensity will not be applied in the routine for obtaining the MPB regression.