What is the best way to do this (making mask and blending two layers)?

[milosh]

Hello everyone,

I have a question about post-processing.
I was faced with this problem while trying to create an HDR out of three exposures.
The scene has one very bright spot (a street lamp on a building wall) and when I fine tuned all the settings in Photomatix, the lamp was heavily blown out. I noticed that by lowering White point setting I can recover the lamp, but with such low White point, I couldn't recreate the overall contrast I had with previous (high White point) setting.
I wanted to keep that contrast, so I took the White point setting back where it was.

When I imported the tonemapped image in Photoshop, I also created a new image from the first exposure (the one in which the lamp is not blown out). Then I made a selection on this new image and added a mask to it (I blurred the mask with Gaussian blur, radius 25). The selection consists of the lamp and a tiny bit of space around it (the brightest part of the wall).
Then, when I put the new image with the mask above the tonemapped image, the problem appears, I can not achieve a good (smooth) transition between the tonemapped image (the background layer) and the new image (with mask) above it. I tried to change the selection size and blur radius, then I experimented with blend modes for the new layer and I chose it to be Pinlight with opacity around 60.
I also couldn't make a larger selection and mask because of the differences in light colour and temperature.

There are two attachments below, the first one is just the background layer with the overblown lamp, and the second one is the final version (it is far from perfect, but it's the best I could achieve) with the new layer above background layer.

My question is: what is the best way to do this blending of layers, when there are significant exposure and light colour differences?

Thank you.

[pcr1968]

That is a difficult shot, But there are things that you could try for example, If you were to put your final image in photoshop as well as the underexposed pic, then blend overlay and with a soft eraser wipeout all that you didn't want then just opacity to taste.

Also you could just duplicate your final image, blend as mutiply and then erase and opacity.

Good luck,

[milosh]

Thank you pcr1968, those are good ideas and I will keep them for future needs, since I already finished processing this image. The result I got has some flaws when viewed large, but for general online purpose it's good enough. Thank you.