A Microsoft spokeswoman began making sounds of protest when we snapped a few seconds of high-definition video using a feature of Microsoft's new Lumia Camera app, Moment Capture.

She didn't need to, because what the camera captured was a perfectly lovely still image. And that's the point of Microsoft's new app.

On Tuesday night, just before Microsoft was scheduled to lift the curtain on its new consumer-oriented Windows 10 preview, Microsoft's Sami Niemi, the man overseeing Microsoft's photography experience, demoed the new Lumia Camera app. Microsoft is shipping Lumia Camera with the Lumia 435 and Lumia 532, but it'll eventually arrive on the Lumia 1520, Icon, 830 and 930 handsets as well.

Lumia Camera is often thought of in the same breath as Lumia Denim, a firmware and OS update that brings phones in line with Windows 8.1 Update. But Lumia Camera won't be made available to every phone, Niemi said, in part because of the limitations of the hardware.

Lumia Camera is made up of four major improvements: quicker app load and shot-to-shot times; Moment Capture, which mines video for still images; Rich Capture, which adds some nifty post-processing; and general improvements in low-light photography.

Why this matters: Apple designed an excellent camera into the iPhone, and Samsung's cameras--though chock-full of frankly unnecessary features in some models--are no slouches, either. Lumia's camera hardware, however, has had a well-deserved reputation for image quality, complete with manual camera controls that allow you to control exposure, shutter speed, and more. But they're also clunky. In a world where imaging "improvements" include filters and stickers, Lumia Camera provides practical improvements to the Lumia line.

Four solid upgrades

But let's start with the obvious: On phones like the gigantic Lumia 1520, actually opening the camera app and taking the first photo can take several seconds--a lifetime at a sporting event or capturing a baby's first steps. Lumia Camera solves this. Tapping the app icon launches Lumia Camera almost instantaneously--still a bit slower than camera apps on other platforms, it appeared, but not really enough to matter. Because Lumia Camera constantly autofocuses, shutter lag appears to have decreased from over a second to 0.3 seconds or so--not perfect, but not bad, either.

Moment Capture takes a complementary approach: Once the camera app is loaded, how do you ensure that you never actually miss a picture? By continuously shooting video, of course. With a long press of the camera button, the Lumia phone begins recording 4K-quality video at 24 frames per second. Rather than try to have you snap photos as fast as possible--which on the Lumia appeared to be about three shots per two seconds--Moment Capture takes the recording and allows you to step through the video, saving any frame you'd like as an 8-megapixel image. Chances are good at least one of those images will be a good shot.

Not a still image, though, mind you. Lumia cameras generally save two images: a lower-resolution one for sharing, and a higher-resolution version for archiving. Microsoft is encouraging users to save "Living Images"--a still image with a separate "sidecar" file with a fraction of a second of video attached. The idea is to give a bit of life to an otherwise static shot, Niemi explained.

We referred to the Rich Capture feature as one to watch when Microsoft announced the Lumia Camera improvements last September, and that still seems to be the case. Rich Capture snaps several quick photos of your subject. The demo Niemi showed used a normal exposure and a flash, but it apparently works with HDR as well. After the shots are taken, Rich Capture allows you to adjust the flash after you've taken the photo, to find the right combination of natural lighting and a focused flash.

That's a pretty nifty trick--and one that requires some significant computational power, as well. What's not clear is exactly why cameras like the Lumia 1020 won't get the Lumia Camera upgrade--and even that's not set in stone, apparently. But it does have to do with the limitations of the hardware, Niemi said.

We weren't able to test the low-light capabilities of the new Lumia Camera app, but Microsoft's promised us a review unit so we can spend some quality time with the app in the near future. And as for Windows 10 on Microsoft's phones? Niemi declined to comment, but he did say we'd hear more at Wednesday's event. At this juncture, however, Lumia Camera looks like a selling point all by itself.