Live composite and foreground exposure

Started 4 months ago | Questions thread
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DaPonti Contributing Member • Posts: 587
Live composite and foreground exposure


I was recently somewhere without too much light pollution so decided to try light composite for star trails. On one picture I tried to include a sign in the foreground, and since it was quite dark, I had to use my phone flashlight to light it during part of the exposure. From a 25 seconds exposure, I found that about 15 seconds of flashlight was more than enough.

Pictures below are JPEG straight out of the camera, just resized.

The first picture shows a single shot.

Once I was satisfied with the settings I moved to light composite, did the same thing for  the base exposure and started shooting. The picture below shows live composite with just 1 shot.

As you can see the foreground is all dark, which is why I stopped as soon as I saw the preview. I tried again a couple of times, but the results were always the same: with a single shot I get light in the foreground, with live exposure it… disappears.

As I mentioned, I was only lighting the sign for about 15 seconds, so I would stop the flashlight before the end of the first exposure. But still… this looks as if I hadn't used the flashlight at all. I didn't want to spend too long experimenting so decided to go with it and merge the foreground later if needed.

But I'm curious to understand why I get such result. I just can't understand how the "base shot" in live composite is different from a normal shot if I use the same settings.

FYI this is what it looks like after many exposures, the foreground is still completely dark and I didn't try to light it during one of the subsequent exposure (not the first short) as I was afraid to ruin it. Maybe it'd have worked?

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