Pictures in indoor light

[mmcirvin]

People who start playing around with little digital cameras soon discover that, to an even greater degree than with film, it's hard to shoot indoors. You can use the flash, but the built-in flash on little cameras is usually nothing special, and it doesn't produce the best-looking pictures if you rely on it. If you don't use the flash, the pictures tend to turn out really blurry, or blotchy and grainy, or just plain dark. If they're too dark you can lighten them up after the fact, but that doesn't help with the other problems; in fact, it usually makes the blotch and grain look worse.

If there isn't a lot of light, and there's no way to make more, there are three ways a digital camera can try to adapt to that. It can widen the aperture, it can lengthen the exposure time, and it can electronically amplify the signal from the CCD sensor. (A fourth way is to digitally brighten the picture, but aside from some possible advantage from doing this prior to image compression, that's no better than when you do it in Photoshop.) Cameras make use of all these methods, but they have limits and tradeoffs.

Aperture is physically limited by the design of the lens. A pocket camera with a little 3x or 4x zoom lens usually can't manage a very wide aperture if the lens is zoomed in at all. This is measured in the peculiar photographic notation of F numbers or F-stops, sometimes written, say, F2.7 or f/2.7. A smaller F number means that more light is let in to hit each pixel (it's an inverse-square relation). Most cameras these days, apart from some ultra-compact models, seem to be able to manage somewhere around f/2.7 or f/2.8 at the wide-angle end. But when they're zoomed in to, say, 3x, that often narrows to an f/5 or worse. The ultra-zoom cameras with big lenses can do better than that, but you can't put them in your pocket—and even they don't do much better than f/2.7 at the wide end; they just don't get as bad when you zoom them. A typical pocket camera shooting indoors is probably already pushing its aperture as far as it will go.

Increasing the exposure time helps, but the big problem there is motion blur. If you're holding the camera in your hands, which is likely what you're doing at an indoor social event, your hands are going to shake enough to blur out the picture if the shutter is open more than a small fraction of a second. Image stabilization can help with that, which is why I think it's a good feature to have. If people are moving around, though, that's another source of motion blur that image stabilization won't help you with.

Finally, the camera can boost its sensitivity by amplifying the CCD signal. The problem with this is that it's also amplifying the noise from the chip, which can be considerable, particularly with the little sensors in pocket cameras. That produces the blotchy, grainy effects that you see in pictures taken in low light.

The amplification is measured by very approximate comparison to the old notion of ISO film speed. Most cameras do really well around ISO 100 or lower, and usably well at ISO 200; around ISO 400 the picture starts to get kind of bad, and the ISO 800 or 1000 modes that some cameras have tend to be nearly unusable, much worse-looking than 1000-speed film. So most people who are into digital photography learn to shoot mostly at low ISO equivalent speeds, and do what they can to either introduce more light or minimize motion in the frame.

That's why I think it's so interesting that this Fujifilm camera claimed to have a new high-sensitivity CCD actually seems to be living up to expectations. I haven't actually used the thing myself, and it sounds as if the ability to go up to ISO 3200 is mostly a marketing bullet point; but if it can really take good-looking photos at ISO 800 as claimed, this could make casual indoor photography a lot easier. It's cool that Fujifilm is starting out introducing this technology in a low-mid-range, point-and-shoot camera instead of some pricey enthusiasts' model.

Simultaneously, image stabilization, which helps somewhat when dealing with longer exposure times, is starting to appear not just in ultra-zoom cameras, but in some compact pocket cameras as well. Just imagine what's going to happen when high-sensitivity CCDs and image stabilization start to appear in the same models: maybe someday we're all going to be able to take for granted that we can shoot without flash (or just using a little bit of flash as a supplement) in indoor light.

Comments

[kodi]

I've seen it explained in more than one place (but I don't remember where any of those places were, now) that because high-resolution CCDs are more sensitive to the angle of incidence (I assume this is because it results in more chromatic aberration than with film?), lenses faster than f/2.7 or so aren't viable for most CCDs. My ancient Mavica FD-71 had a f/1.8 lens, and took brilliant low-light pictures compared to just about anything I've seen since.

[mmcirvin.livejournal.com]

Yeah, those early Mavicas could do things that sound amazing by later standards just because there was no expectation of high-res images. They often had incredibly long zooms too, because they were basically video cameras; it's easier to build a long zoom when the sensor is that tiny.

[mmcirvin.livejournal.com]

I assume this is because it results in more chromatic aberration than with film?

I suppose the difference from film is that unless you've got a very expensive CCD, it's much smaller than a 35mm frame, so the fringes from chromatic aberration are going to be correspondingly magnified in the final image. (Whereas with the old Mavica this didn't matter much because the resolution was low enough that the pixels were still fairly physically large.)

[mskala.livejournal.com]

This may be a very optically naive thing to say, but isn't the basic issue of chromatic aberration that the lens magnifies different wavelengths by different amounts, and in that case, would it be possible to electronically zoom the colour channels by different amounts to compensate for it?

[mmcirvin.livejournal.com]

I think that's coming someday, because in fact, there are laborious methods for doing that in post-production (http://hugin.sourceforge.net/tutorials/tca/en.shtml). With sufficient computing power, you could have some degree of digital de-CAing in the camera.

[mmcirvin.livejournal.com]

...though I should add that the ability to do that only goes so far if the sensor just has the three color channels, because there would be chromatic aberration within the range of each color channel as well, smearing out the picture.

[mskala.livejournal.com]

To be sure, but it seems like every little bit would help.

[westacular.livejournal.com]

Well, there's other drawbacks to wider apertures, as I'm sure you're aware, but that's the least of your worries if you don't have enough light.

ALSO: The sensors in DSLRs tend to have really high sensitivity, but that's at the cost of much larger and higher quality chips.

On the consumer end, sensitivities seem to be improving at an evolutionary rather than revolutionary rate. Companies keep promising these amazingly sensitive cameras but the reviews always end up being "TOO MUCH NOISE REDUCTION" or "Well, it is somewhat better...".

Having said that, this F30 model you linked to looks like a very solid step in the right direction.

[mmcirvin.livejournal.com]

Yeah, it seems a common thing to do these days is to try to get around the noise at high ISO by stomping on the picture with an enormous amount of digital noise reduction, which smears out all the fine details as well.

I get the impression that good high-ISO sensors have been a big research project at Fuji for several years. They've long been into slightly weird sensors; early on, they used those CCDs with a 45-degree canted sensor grid that interpolated half the pixels, and advertised inflated pixel counts that irritated all the camera geeks.

[mmcirvin.livejournal.com]

...but, as you said, most of the cameras they've actually released up to now were more in the "well, it is somewhat better..." category.

[paracelsvs.livejournal.com]

Here's a fun trick for indoor photography with a small digital camera:

Get a small mirror (with no frame). Hold it in front of the flash at a 30-45 degree angle, aiming the flash up into the ceiling.

This produces pictures that are still a bit dark (since the flash is not quite powerful enough to light up the room properly), but that are still much sharper than pictures taken without a flash, and with much more appealing lighting than a straight flash shot, with the over-exposed foreground, under-exposed background and red eyes.

It's great for party photography (once you get past the issue of having to explain to people what you are doing):

[mmcirvin.livejournal.com]

I've often thought about trying something like that, but never bothered to carry around the requisite pocket mirror.

[mmcirvin.livejournal.com]

...Somebody should make a little camera with the ability to point the flash upward.

The problem with that idea is that, as you noted, most flashes aren't powerful enough to light up a room this way, and it would be difficult for the camera to meter it automatically, so it would only be a mode for people who knew what they were doing. Maybe they could make it closer to idiot-proof by just having the camera do an internal Auto Levels after taking the picture.