Trouble finding area of a circular ROI in threshold image

[CJB]

Hi everybody.

I'm having trouble finding the area of a circular ROI in an image created by image>threshold.  In the parent image, I use analyze > set scale to define the length of a line in cm (8.4cm) and tick "Global".  If I now draw a circular ROI and go to analyze > measure, it returns a sensible value for the area (~55cm^2).

When I set the threshold of the image by adjust > threshold and click "apply", I generate a new image.  If I draw a line of similar length and go to analyze > measure, it returns a sensible value (~8.4cm).  However, if I now draw a circular ROI of similar area to the previous circle, it returns a nonsense value for the area (~1.3cm^2).

Does anyone have any reason why this should be so?  Thanks in advance.

[CJB]

I'm not sure if I accidentally deleted a response to this message but here is a response that was sent to my email:

Hi,

Do you have the "Limit to threshold" option in Analyze>Set Measurements enabled? That might make a difference.

Best regards,

-wayne

Anyway, the answer was bang on.  The "limit to threshold" option was enabled, which meant I was only getting the area of the particles and not the area of the larger ROI.  Thanks Wayne!  The previous frustration is now superceded by a calm satisfaction.