Blur around masking a subject when changing exposure

[OZINC]

Hi everyone, I am trying to make a person pop by darkening the background through exposure then brightening the person through a mask and adjusting the exposure. The problem is I get a blurred halo around the hair when I adjust the mask with exposure. 

Process 

1.   Adjust whole photo to get the background exposure correct.

2.  Mask the person through the subject option.

3.  Adjust the exposure of the person to preferred setting.  Once done you get a large blurred halo around the persons head.    

How do you stop that from happening?  Is this a bug or technique?

[JohanElzenga]

It's a limitation of the masking options in Lightroom. I have found that using object recognition often creates better masks, but you will always have to manually remove the remaining halos. The way you can try to do that is by adding a brush to the mask. Set the brush to 'Auto Masking', choose a brush size that covers a nice part of the halo and then carefully place the little cross in the center of the brush in the area you want to add. Do not paint, but click once for each area you want to add.

[OZINC]

Thanks Johan for your response.  The tool is so close to being extremely powerful for me.  I did try your recommendations from what I understand though with no luck.  I did use the subtrack on the mask and I did not get the halo (as you would expect), but too much difference in colour from the forward hair and the sides.  As soon as you touch exposure around that hair the halo starts (note I did adjust sliders hightlights,shawdows,whites and black during this test).  I am not a Photoshop expert but might try to see what I can do there.