Pictures in indoor light
Jul. 25th, 2006 09:05 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
mmcirvinPeople 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.
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.
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Date: 2006-07-26 01:26 pm (UTC)