DennisN said:
Tonight I tried something for fun which I had never done before.
It was a full moon and there was a distinct sphere of moonlight around it, and I got the idea of trying to take a photo of both the Moon itself with details and the moonlight around it.
To do this in one shot is AFAIK impossible with ordinary gear (maybe there is some special equipment which can dim a particular area only, I don't know). The reason is that you need very different exposure times for the Moon and moonlight.
So I shot it using two different exposure times, and then I merged them in Photoshop.
View attachment 292608
Photo info:
Moonlight shot at ISO 1600, 1/20 s exposure.
Moon shot at ISO 1600, 1/1000 s exposure, 25% of 50 stacked photos.
Gear: Sony A6000 with a Canon FD 135mm f/3.5 and a Canon 2x Teleconverter.
That's a beautiful image.
Yes, it's true that sometimes it is necessary to take multiple exposures (or separate stacks, each stack using a different exposure setting) for different objects/targets/facets in the same frame. Then combine them into a single image in post-processing.
I'm using "exposure setting" here liberally, because it could mean change the camera's gain/ISO setting, not just the exposure time.
Here's an image I took of the Great Conjunction on Dec. 21st, 2020. The image was made by capturing tens of thousands of individual frames, over the course of about 25 minutes, using a few different camera gain settings to increase dynamic range. They were then stacked using lucky imaging techniques and combined.
There's no way I could have gotten all of Jupiter, Saturn, and the moons using a single set of exposure time and gain setting, without blowing highlights or having something getting lost in the noise.
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In normal, terrestrial photography, there's a whole technique called "HDR," standing for "High Dynamic Range," where the same subject is photographed typically three times, each with a different exposure, then those exposures are combined in post processing. Here is an article on it.
https://www.digitaltrends.com/photography/what-is-hdr-photography/
Note that the same term and initialism is used to describe TVs and computer monitors with high brightness and deep darks, which have almost nothing to do with HDR photography. 'Just wanted to point that out: HDR photography and HDR monitors are different beasts.
That said, some rendering engines in video games use HDR techniques similar to HDR photography, even if they don't support HDR monitors. And other video games are capable of supporting HDR monitors.
So yeah, when looking up the term "HDR" and/or "High Dynamic Range," it might refer to different things depending on the context.