Hi Mykola,
yes, I can reproduce your problem, it occurs if the first lane has a lower maximum than one of the others. It seems that autoscaling is used for the height, so the highest maximum over all of the lanes determines the scale factor.
One can't disable this autoscaling with Edit>Options>Profile Plot Options, but I found a workaround:
Apply a scale to your gel image, e.g. with the following macro (should be one line; mind line breaks introduced by the mailer):
run("Calibrate...", "function=[Straight Line] unit=value text1=[0 255] text2=[0 255]");
Then you should get consistent values.
Michael
________________________________________________________________
On Sep 12, 2012, at 06:23, Mamenko, Mykola wrote:
> Hello everyone,
>
> I recently started to use ImageJ to quantify my blots and noticed a weird thing about the band area calculation.
>
> To my understanding ImageJ should return similar values of the band areas, regardless of the number of lanes being plotted/selected simultaneously (given the area of selection rectangular is the same).
>
> Perhaps, my particular case would be more illustrative. The blot for quantification had 12 lanes in it. I used a rectangular selection tool (the dimensions of the rectangular were 145x65 pixels). When only the first lane was selected and plotted, ImageJ would return the area of the band as ~54k. But if all 12 lanes were plotted (with the same rectangular tool dimensions), the calculated area of the band in the first lane dropped to ~35k. The less lanes are plotted/selected - the closer calculated first band area is to the 1 lane selection measurement.
>
> The background was homogeneous for all lanes.
>
> Thank you for you consideration. Let me apologize for potentially unwise questions raised here. Any comments would be highly appreciated.
>
> Best regards,
> Mykola Mamenko.
>
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