When a manufacturer describes their sensor as an "APS-C" sensor, they are referring to its size. The problem is, that size differs based on manufacturer.
Why It Matters
The size of the image sensor determines the surface area available for collecting light. More light generally translates into higher image quality. This means a large sensor can produce higher quality images than a smaller sensor even if the smaller sensor boosts a higher number of pixels.
Increasing pixel count without changing the size of the sensor requires decreasing the size of the individual pixels. (More accurate, it requires the size of the area used to capture light referred to as a photosite.) Smaller pixels increase image noise, especially in low light conditions.
Sensor size does impact camera design. Larger sensors require larger lenses. This in turn requires larger camera bodies, making larger image sensors impractical for phones and compact cameras. Larger sensors also cost more to manufacture. Manufacturers use smaller sensors to keep costs down.
The smaller target area provided by smaller sensors impacts the lens used. Using a lens designed to be used with a larger sensor will result in part of the image falling outside the surface area of the sensor. Part of the image seen in the viewfinder will be lost. Smaller sensors require wider angle lenses to properly focus the image onto the sensor.
Sensor Sizes
he largest sensor size found in consumer level cameras are known as Full Frame sensors. These have the same dimensions as 35mm film. Lenses designed for 35mm film cameras will work exactly the same if used with a camera using a full frame sensor.
Next in size are APS-H sensors, followed by APS-C sensors. The size of the latter depends on the manufacturer.
Next in order of size comes 1.5", Micro Four Thirds 4/3", 1", 1/1.2", 2/3", 1/1.7", 1/2.3" and finally 1/3.2". The use of fractional divisors makes some of the sizes a little hard to understand. (Really, 1/3.2"?)
| Converted To Decimal Form | |
| 1.5 | 1.5000 |
| 4/3 | 1.3333 |
| 1 | 1.0000 |
| 1/1.2 | 0.8333 |
| 2/3 | 0.6667 |
| 1/1.7 | 0.5882 |
| 1/2.3 | 0.4348 |
| 1/3.2 | 0.3125 |
This makes the relative size a little easier to understand. A 1/3.2" sensor is almost 5 times smaller than a 1.5" sensor. It get's a little more confusing when attempting to compare the "inch" based measurements to full frame and APS sized sensors. The inch based measurement actually refers to the size of the lens, not the diagonal measurement of the sensor. This increases the size given by about 50%. (Multiply the given figure by 2/3 to get the approximate diagonal size of the sensor.)
Full frame and APS sensors only provide mm measurements for size. To make comparison a little easier, according to my calculations full frame sensors are the equivalent to 2.77" in the above system. APS-H and APS-C sensors fall between 2.555 and 1.5. APS-C is roughly 1.8" and APS-H roughly 2.1".
For a visual depiction of related size try this gizmag sensor size guide article.
Wikipedia has an article on Image sensor formats that includes a list of sizes at the bottom, including diagonal dimensions.
For those that are interested, manufacturers do make cameras utilizing sensors larger than full frame sensors. The next step up are referred to as medium format cameras. Large format cameras use even larger image sensors.
The width and height of medium format sensors are roughly 50% larger than that of full frame sensors. (In "inch" terms, roughly 4.3".)
Medium format digital cameras are used by many professional photographers. These sensors offer up to 80 megapixels. Combining this number of pixels with the larger sensor size provides image quality unmatched by most consumer cameras.
In addition to the above "inch" system, the sensor's surface area will also give consumers a good idea how sensors compare to each other in regards to image quality. A medium format sensor has a surface area of over 2100 square mm. Full frame is 860 square mm. APS-C ranges from 330 to 380. A 1/3.2" sensor has a surface area of just 15 square mm.
The extremely small surface area available for that last sensor results in it being far less capable of capturing existing light. It is going to be far more reliant on good lighting conditions than the larger sensors. This doesn't mean the camera will be incapable of taking good pictures, just more reliant on existing light. (My old Kodak EasyShare ZD 710 has a 1/2.5" sensor. It takes excellent macro flower pictures in full sunlight.)
When Buying a Camera
The impact sensor size has on image quality means that consumers should always consider sensor size when purchasing a new camera. The problem is that sensor size data is not always easy to find. The only source may be the manufacturer's web site. The manufacturer should mention the sensor size on the specifications (spec) page for each camera model.
Online stores generally include camera specification on the product page. Check the specs when shopping online.
Brick and mortar stores may be a bit more problematic. The material provided may not list sensor size. Check online if not available at the store.
No comments:
Post a Comment