In the previous post, see Sensors I , learn or review the following:
(one recommended having read the previous post for a better understanding of this)
.- recall the factors that involved in the quality of a photo.
.- Sensor describe the camera.
.- learned the meaning of Signal and Noise .
.- learned what the Signal to Noise .
.- remember how to set the ISO value .
.- learned what are the photosites.
.- We saw how it relates to the size of the photosites with signal to noise ratio.
.- We could see how it affects the ISO in some photos taken with a camera (point & shoot) small sensor, generating a tremendous amount of noise at high ISO values.
.- We learned that if we have sensors of the same resolution, size if it influences the quality, it has, the larger sensors, larger photosites (yellow graph).
.- We saw how, if a sensor of a given size will increase the resolution, the photosites should, logically, be smaller in order to put more items in the same area (blue graph).
.- not necessarily learned that a larger sensor always mean quality.
Well, industrially manufactured sensors of different sizes and for different uses, but basically we're going to have to deal with some of them, how such as "Full Frame" (full), APS C, (one of the most common sizes in DSLR cameras), or Four Thirds 4 / 3 (used by Olympus and Panasonic), and a couple of sizes used in cameras Point & Shoot and Brige Cameras (also called Prosumer).
Full Frame sensors have the same area as the film of 35 mm (36 x 24 mm.) And this size is against all comparisons are made and equivalents, especially to define the effective focal length ( LFE).
few exceptions (very few) Point & Shoot cameras and so-called Bridge or Prosumer share a sensor size of 1/2.3 cryptically called ". The following is a list of common sensors used in these cameras (small sensors).
Some of the more common smaller sensors
sensors in blue are most common in small chambers,
all measurements are in millimeters .
an exercise of reasoning to understand how to distribute the photosites on the sensor, and how to calculate its size:
An example, my wife has a Panasonic Lumix FZ 100 , this is a good camera category or Prosumer Bridge is among the best (or best) of its level, many interesting features and other fantasy, a zoom ranging from 25 mm. to 600 mm. Effective Focal Length (a very good 24x zoom), has 14.1-megapixel (a good decision!), y. .. a 1/2.3 sensor! ??
If we see in the table above, we have that the sensor has a size of 6.16 mm . x 4.62 mm. , if we multiply both measures an area of \u200b\u200b28.46 mm. square, looking at the specifications of the camera have their resolution is distributed in 4.320 3.240 pixels and vertical pixels horixontales .
If we divide the number of horizontal pixels between the horizontal dimension of the sensor, we obtain as a result the number of pixels per sensor that captures miliímetro horizontally:
4.320 pix. / 6.16 mm. = 701.30 pixels x mm. (In the horizontal direction)
Now do the same thing in the vertical direction:
3.240 pix. / 4.62 mm. = 701.30 pixels x mm. (In the vertical direction)
From these calculations we can assume that the linear density (pixels x mm.) Is the same both horizontally and vertically, in each linear inch this sensor is 701.3 photosites (pixels .)
have to know how many photosites on a square inch, multiply 701.3 x 701.3, with which we get that this sensor has 491.821 photosites per square millimeter. This is almost half a million photosites in each millimeter square.
But, all this display of calculations ... it good for? ... serves to give us an idea of \u200b\u200bhow small are the photosites or components of a sensor like this is more so now let's see how each measures so we can compare them with other sensor photosites bigger.
If we divide an inch between the number of photosites, we obtain the linear measurement of each photosite expressed in thousandths of a millimeter or micron (micron), ie millionths of a meter. Thus:
1 / 701.3 = 1.43 microns. (Each photosite measures 1.43 microns in diameter.)
We assume that the photosites are round or square area (it's round), but we need to calculate the area of \u200b\u200beach photosite needed to do comparisons.
The important measure is the area!
Because most area captures more photons.
area of \u200b\u200bcircle = radius squared multiplied by pi. (Remember?)
==> A = 0715 ^ 2 x 3.1416 = 1.6 square microns
Thus, a circular photosite of 1.43 microns in diameter, have an area of 1.6 microns square.
If we compare the size of a photosite of a small sensor (camera point & shoot and bridge) with a DSLR (reflex), we realize the size difference.
I have an Olympus E 30 from 12.30 megapixel Four Thirds sensor of 17.30 mm. X 13 mm. If we make the same calculations, we see that the photosites of the sensor measured 4.30 microns linear, which is much larger, and if we do the calculations to find the area, we think this is 14.5 square microns.
Making the comparison (by dividing the latter area between the former), we have the photosites of my camera are more than 9 times bigger than the sensor of the Lumix FZ 100.
Now we see why the image quality of an SLR camera is far superior to that of a small camera (for those who do not have interchangeable lenses).
Following the same line, the Canon EOS cameras, model 7D - 60D-T3i, for example, have photosites of 4.31 microns in diameter, and therefore of 14.58 square microns area.
In comparison with my Olympus, we see that virtually the same size, but comparison FZ sensor 100, are still enormous.
I hope I explained and demonstrated that the issue IS NOT sensor size, ES the size of the photosites or elements of the sensor, referred to the area size.
Basically when you know about this issue talk about the size of the sensor, talk about the difference between DSLR cameras and which are not., As a Four Thirds sensor measuring 17.3 x 13 mm. and Canon's APS C measures 22.30 x 14.90 mm, it is true that the sensor is bigger, but what really matters is the size of the photosites, and these are practically the same ... let me understand?
And when those who do not speak or have not investigated the size of the sensor, ONLY talk about it, regardless of anything else.
worth mentioning that there are some cameras point & shoot taking high quality photos, good, better quality than the other P & S, but never of the quality of a DSLR. They do this by putting a little larger sensors, and lower the resolution ... this is, if not the right way to grow the photosites, more area and less number of photosites in the area ... I mean?
Well some of these cameras are the LX5 Lumix and Olympus XZ-1, its photosites are 50% larger than those of normal small cameras, but their prices are also larger. We also have the Canon Powershot G12 and Nikon P 7000 with its sensors 1/1.7 "and 10.1 megapixels. I do not know if there are others in this category, I will leave that to your research.
Then I pass a link to a Microsoft Excel table I made for you, in this table is a list of different brands and models of cameras, at least the most representative in terms of sensor size in This table is the sensor size and the number of megapixels that this is, then comes a red zone with sensor data, and their vertical and horizontal measures, the same bias and its area in square millimeters.
Then, in the blue area are data from photosites (pixels), the amount both horizontally and vertically, the number of photosites per millimeter in both directions, the density in pixels per square millimeter, the size (diameter) of micron photosite and finally the most important figure, the photosite area in square microns, this is the one used for comparison.
hope that with these two articles for the sensors, make it very clear that the cameras P & S, the bridge or prosumer, much less cell phones can compete with a DSLR (reflex).
Ah, it is remarkable the size of the photosites of the Nikon D700, a camera with better signal to noise ratio, so you can realizr shots with very high ISO values \u200b\u200bwith little loss of quality.
EYE, the fact that a camera comes with the possibility of raising the ISO to stratospheric figures does not necessarily mean that those values \u200b\u200bare used in practice.
Here comes the Excel link box: SENSORS
Other links:
Sensor Sizes in DPReview
Sensor Sizes in Cambridge in Colour
NOTE: The sensor size is determinate to find the multiplication factor, and / or the effective focal length (LFE) , which is directly connected to its diagonal, but we'll see later
I hope I have exhausted the subject (here come my knowledge).
See you at the next post!
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