Guess it's time for a DSLR...

March 13, 2007 1:28 PM

Why do point-and-shoot digital cameras have such small sensors?

I'm about to return my brand new Canon A710IS, because I can't see any improvement in image quality over my nearly 3-year-old Olympus C7000Z. The electronics are much better (most noticeable in autofocus), but the noise, poor color response, and fuzziness are virtually indistinguishable. Even the image stabilization doesn't seem to help that much -- it can turn an unusable photo into a postcard-quality one, but it can't turn a postcard-quality photo into a print-quality one.

After some research, I'm convinced that the problem is the sensor size. The A710IS sensor is actually smaller than the one in the C7000Z. I don't understand this. Why is it that you can only get a larger sensor in a DSLR? Why are the P&S manufacturers putting in better lenses, better electronics, and all sorts of fancy post-processing tricks, but can't seem to improve the one part that actually generates the image itself?

posted by bjrubble to Technology (21 answers total)

because nobody would buy the more expensive, interchangeable-lens (ie, potentially more lucrative) DSLRs?
posted by matteo at 1:34 PM on March 13, 2007

Because they haven't figured out a good way to advertise it yet. And if people don't know they want it, they won't pay extra for it.
posted by smackfu at 1:49 PM on March 13, 2007

Noise is the only real downside of a small sensor. Fuzziness is either from bad optics or from bad noise-reduction.

The thing about "point and shoot" also known as "compact" cameras is that they're small and cheap. Big sensors = big cameras, and more expensive. If your sensor is larger your lens needs to be further from it, and needs to be larger to collect more light to cover the increased area. So why would I buy a large expensive point and shoot, over a large expensive SLR?

SLRs do have auto modes where you can point-and-shoot with them.
posted by aubilenon at 1:55 PM on March 13, 2007

Larger sensors are more expensive too produce and require larger and better lenses to focus light onto them.

Imagine a dSLR-sized sensor in your tiny P&S, and how each part would have to be bigger, forcing the next part out and then it gets bigger and moves the next part out until you have a dSLR about the size of an entry-level like a Canon XT.
posted by deadfather at 2:00 PM on March 13, 2007

In the P&S market, camera size is a bigger selling point than low-noise and high ISO performance. Bigger sensors require bigger lenses, more battery power, etc., making for a bigger and less competitive camera. I guess not that many people are gonna use a A710IS to take dim light pictures which are likely to expose the tiny camera's noise problems. Though, in good light, I do think today's P&S cameras (especially with IS) can take great pictures.
posted by bluejayk at 2:07 PM on March 13, 2007

Best answer: Noise is the only real downside of a small sensor. Fuzziness is either from bad optics or from bad noise-reduction.

Well, it takes extremely good optics to resolve down to the miniscule pixel size of these tiny, 7+ megapixel sensors. A tiny, plastic lens can only do so much.

One might also argue that another very significant effect of a small sensor is the expansion of depth of field, which prevents the smooth, out-of-focus background that is the telltale sign of SLR photography.

I should clarify my above comment. The only that really needs to get bigger with a bigger sensor is the lens. But it needs to get a LOT bigger. See the glass on the standard zoom lenses that are paired with entry-level dSLRs? They are that size because they have to be. Try incorporating that into a P&S.

It's true that these companies do think about protecting their SLR line. But many companies don't have an SLR line, or have a really tiny one.
posted by deadfather at 2:13 PM on March 13, 2007

I guess not that many people are gonna use a A710IS to take dim light pictures which are likely to expose the tiny camera's noise problems.

The sad thing is the sensors are so small that the definition of "dim light" is pretty ridiculous. In an indoor setting, where you and I can see perfectly well, most point and shoot cameras will still need to rachet up to 200 ISO (high noise) to get a picture free from motion blur. In a truly dim setting (restaurant at night, bar/club), the P&S is entirely useless. Most people will resort to using the flash at this point, which brings along all sorts of new problems.

I completely sympathize with the asker. There are situations where I don't want to lug my SLR around, so I bring my small Canon and suffer the consequences. I will typically crank it to ISO 400 and try to post process the noise as much as possible.
posted by knave at 2:16 PM on March 13, 2007

I've had a lot of luck using a tripod with my Canon A85 in a low-light situation. Even a small one like this will do wonders.
posted by Lynsey at 2:40 PM on March 13, 2007

As someone who doesn't know that much about photography, I have to ask… if a bigger sensor would require a full-size lens, how were they able to make point-and-shoot 35mm film cameras? As far as I know, even the DSLR sensors are smaller than 35mm film.
posted by designbot at 2:57 PM on March 13, 2007

Fuzziness is either from bad optics or from bad noise-reduction.

Don't forget diffraction effects.

if a bigger sensor would require a full-size lens, how were they able to make point-and-shoot 35mm film cameras? As far as I know, even the DSLR sensors are smaller than 35mm film.

Most DSLR sensors are smaller than 35 mm filme, and Canon, Nikon, and Sigma (among others) make lenses specifically for certain DSLRs that take advantage of this by being smaller and lighter and leaving less room at the camera end for the mirror to flip up (since the mirror is also smaller. On the other hand, Canon makes several DSLRs with full-frame (i.e. equivalent in size to 35mm film) cameras; the technology is described here. As one would predict given the good information in the comments above, these cameras are known for exceptional low-light performance, among other things (like being really expensive).
posted by TedW at 3:11 PM on March 13, 2007

Best answer: designbot, I think a potential issue is with the way sensors are built, and how they perform compared to film. You can think of the individual pixels on a CMOS sensor as being little buckets that gather light. If the light is coming in at an extreme angle, less of it gets into the bucket. So you will find the outer pixels on a large sensor starved for light by making the light travel at extreme angles to hit the edges of the sensor. The angle doesn't matter nearly as much for film. Check out this page for a more detailed explanation.
posted by knave at 3:13 PM on March 13, 2007

Best answer: P&S cameras have almost always taken great liberties with "sensor size", even going back to the film age. Camera companies were CONSTANTLY foisting off smaller film formats for cameras. Remember "110" film? Or more recently the "APS" systems? These were film formats with about 1/4 the area of 35mm film. Most consumers either didn't care or couldn't figure out why their pictures looked terrible at sizes larger that 4x6"

A bigger sensor does not require a full size lens. It does usually require a higher quality lens, which is usually somewhat larger, more expensive, better designed, harder to make, etc. Think of it this was: a lense produces a "cone" of light behind it. Where it intersects with the film or the digital sensor, it makes a circle. That circle has to completely overlap the rectangular film/sensor area, or you'll have circular dark edges. The size of the circle at a given distance to the film sensor is a factor of how the lens is designed.

There may be some P&S cameras that have larger sensors, better lens designs, etc. Last time I bought a P&S was a long time ago, for my wife. I made sure to get a 35mm camera, and I made sure it had a good lens (it was a Zeiss lens). I got a lot of good advice from photo.net. Keep in mind that was probably something like 6 years ago so I have no idea if that's still a good resource. There are probably some P&S that are head and shoulders above the rest, at reasonable price points.
posted by RustyBrooks at 3:16 PM on March 13, 2007

That page is interesting, knave. I didn't know about that - my explanation of lens-cone size is from my knowledge of film. I still mostly shoot 4x5 and 8x10 so it'll probably be a long time before I go digital, if I eveer do.
posted by RustyBrooks at 3:18 PM on March 13, 2007

It occurs to me that they could overcome this problem by producing curved sensors (concave on the lens side). The interesting challenge, then, would be to produce a lens that projects a focused image onto a non-flat area. :)
posted by knave at 3:27 PM on March 13, 2007

designbot, you should read this dSLR overview from photo.net. Relevant portions:

Big lenses, big sensor. Canon and Kodak have taken the most obvious approach to the challenge of transitioning from film to digital: build a digital sensor exactly the same size as one frame of 35mm film. The result is a chunk of silicon 24x36mm in size, which is vast compared to the sensor in a point-and-shoot digicam. The benefit of this vast sensor is reduced noise, which looks like grain, in low light/high-ISO situations. The drawback of a vast sensor is that manufacturing a flawless piece of silicon this big is very expensive. The only consumer-priced camera in this category is the 13-megapixel Canon EOS-5D ($2950; check amazon.com for the latest price). If you have a strong back and an unlimited budget, the 16-megapixel Canon EOS-1Ds Mark II ($7000; available at amazon), is a great choice. It is probably the best digital camera made and produces image quality that rivals medium format film (e.g., 6x6cm Hasselblad). The only other full-frame digital SLRs made were the discontinued Kodak DCS Pro SLR/n and SLR/c bodies. The Kodaks were cheaper than the Canon but not quite as functional and the fact that they were discontinued is a good illustration of why you want to buy a digital SLR from a market leader. I own a 5D and have written a full review of the Canon EOS 5D.

Big lenses, small sensor. In order to keep the cost of the body within a range of $700-1500 and allow photographers to use their old 35mm system lenses most digital SLRs fall into this category. The front of the body has the same lens mount as an old film SLR. The back of the body has a sensor that is smaller than the 24x36mm standard frame of an old film SLR. The result is a camera that looks the same as the old film camera but multiplies the magnification of all the lenses. Having a smaller sensor is like cutting the center out of a drugstore proof print. You don't capture all the information on the left and right and top and bottom of the frame. It is as though you took the picture with a telephoto lens. The viewfinder has been adjusted so that what you see optically is what is captured in the digital file. If you're coming from the film world you will need to do a mental adjustment. A 50mm normal perspective lens on a big lens/small sensor camera behaves like an 80mm telephoto lens on a film camera. A 20mm ultra wide-angle lens behaves like a 30-32mm slightly wide angle lens on a film camera. Nearly all the popular digital SLRs fall into this category and their various merits will be discussed below.

Small lenses, small sensor. The biggest problem with the "big lens, small sensor" situation is that photographers are forced to cart around lenses that are much larger, heavier, and, theoretically, more expensive, than they need to be. A big heavy Canon telephoto lens is big and heavy mostly because it is built to cast an image circle large enough to cover a 24x36mm frame but the Canon EOS 30D body's sensor is only 15x22mm in size. Any engineer would look at this "big lens, small sensor" situation and say "Why not come up with a standard reasonable sensor size and then make lenses that are just large enough to cover that sensor with an image?" That's precisely what the Four Thirds consortium did. Olympus and Kodak seem to be the originators of the standard but Fuji, Panasonic, Sanyo, and Sigma have signed on as well according to www.four-thirds.org. This seemed like a great idea at the time (2002) but four years later only three Four Thirds system bodies have been built, all by Olympus, and only a handful of lenses, all from Olympus and Sigma.

If you have a a robust checking account and/or a lot of Canon EOS film camera lenses an unlimited budget the "full-frame" Canon EOS-5D (big lenses/big sensor; medium weight; $2900) is the obvious choice. If you don't need state-of-the-art performance and value compactness above all, the Olympus E System is a reasonable choice (see my review of the Olympus E1 for more detail; the current best buy is a complete starter kit with the E-500 for $790 from amazon). More than 90 percent of photographers, however, will find that the engineering compromise of "big lenses/small sensor" fits their budget and needs. This has led to the introduction of lenses that have the big lens mount for a 35mm film camera but optically cover only the small sensor of a mid-range digital SLR. These are sold as "digital-only lenses" or "digital camera lenses" but in fact they won't work on a full-frame digital SLR--the corners of the image would be black. Canon denotes these lenses as "EF-S", Nikon as "DX".

posted by The Michael The at 3:31 PM on March 13, 2007 [1 favorite]

Unfortunately, what they refer to as "small sensor" in the above article is huge compared to the sensors found in current P&S cameras. It doesn't really help us understand why, other than cost, the smaller cameras are saddled with tiny, noisy sensors.
posted by knave at 3:42 PM on March 13, 2007

I'm with you: big sensors = better photos. Why small sensors? Cost is one big reason. The other is geometry and the desire for small cameras. If you have a tiny sensor then you can get by with a smaller lens and less depth in the camera body. Most of the digital P&S market is driven by small size.

A search for camera sensor sizes turns up some useful articles. dpreview lists the sensor size of all their reviews; maybe there's some way to search it for a point and shoot with a larger sensor.
posted by Nelson at 3:51 PM on March 13, 2007

As far as all-in-one cameras go, the Fuji F40 (and it's predecessors) have the largest sensor. I think the Canon G series is the next closest (there are perhaps others as well).
posted by Good Brain at 3:56 PM on March 13, 2007

Here's 3 good reasons.

Chip yield improves as chips shrink. The natural desire for any chip company is to make smaller chips. If the optical trade-off is acceptable, the camera makers buy the smaller, cheaper sensors.

Most people won't notice or care. Generally, people take most of their photos at close range and usually of other people, something even a crummy ol' 110 can do just fine. Many people can't even notice jpeg aliasing so a little sensor noise or bad color reproduction just gets unnoticed.

The optics on P&S cameras are also tiny because people like tiny, convenient cameras. There isn't any point to adding a large, quality sensor when the lens itself is so lousy.

I was never satisfied by any of the digital P&S cameras I had and finally just went DSLR. It's heavy and bulky but I'm finally happy with the picture quality.
posted by chairface at 6:12 PM on March 13, 2007

Sigma will make the DP1 , a compact with an APS size sensor and a fixed focal length and relatively slow 28mm f/4 lens to keep it compact.

If you define P&S by the size of the camera, this would be the first digital P&S without a small sensor.
posted by Akeem at 2:53 AM on March 14, 2007

Response by poster: Looks like DPReview is looking for the same thing I am, and it ain't there.
posted by bjrubble at 10:04 AM on March 15, 2007