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Nikon DSLR Cameras
D3200
Manually lowering the ISO speed (<100)
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<blockquote data-quote="aroy" data-source="post: 316196" data-attributes="member: 16090"><p>To understand what a lower ISO will do (and what the "LO" range will not, here is a simplified version of how a sensor works.</p><p>. The digital sensor works by accumulating photons. The number of photons is limited by its design. The maximum number of photons that a sensel can hold is called the full well capacity, and that defines the base ISO.</p><p>. There are various types of noise involved in the chain - random, thermal and electrical. For this post I will consider only the noise generated in the sensel.</p><p>. The Dynamic Range (DR) of a sensel is roughly the ratio of the signal at full well capacity to the noise.</p><p>. To increase the ISO, you just amplify the signal from the sensel, and that amplifies the noise also. That is why the best DR is at base ISO, as above that the signal decreases while the noise remains more or less same. If you decrease the signal to simulate lower ISO, you will decrease the noise generated in the sensel, but then other noise components generated further down the stream will increase.</p><p>. After the signal from the sensel is processed it is digitized in an A-D converter. The number of bits in the output is decided on the basis of the speed of conversion and the number of photons in full well. The larger the number of bits in an A-D converter the slower it gets. 16 bits means 64K discrete levels and 14 bits 16K discrete levels. If the full well capacity is less than the number of discrete levels then there is no use having so many levels. The noise (and DR) further reduce the number of levels.</p><p>. Initial sensors had only one A-D converter, so that the process was very slow, as it converted every bit serially. Modern cameras have one A-D converter per row/column as the design may be, hence are much faster.</p><p>. The total burst rate of a camera is dependent on</p><p>- exposure time, including shutter cycling</p><p>- Read time for all sensels</p><p>- A-D conversion</p><p>- Demosaicing </p><p>- Writing to memory</p><p>- clearing the sensor of its charge - initializing it to zero</p><p>Thus a fast A-D and a fast processor are required for fast burst rate. That is one of the reasons that very fast burst rates are limited to 16/18MP sensors. doubling the burst rate from 5fps to 10fps will require the whole chain to be twice as fast. Similarly expanding the sensor from 16MP to 24MP will need 50% faster and from 16MP to 36MP 2.25 faster.</p><p></p><p>Lower ISO.</p><p>To lower the base ISO you have to redesign the sensor for lower ISO (larger full well capacity, etc), which will mean lower MP. Now unless you can up the DR proportionately, there will be no takers for lower ISO. Majority of the DSLR users are either sports, event shooters & press (high burst rate) or cost conscious users (lower the cost the better) or advanced amateurs (high end equipment with general interest). A lower ISO with enhanced DR will not appeal to any.</p><p></p><p> Lower ISO high DR is available with Medium Format, but the costs are 10-40 times that of the current 35mm DSLR, used by those who want excellent DR with great tonality as well as modularity - fashion & advertising requiring large product images and landscape photographers who want to print large. Because of better DR the tonal gradation in medium format is better compared to 35mm.</p></blockquote><p></p>
[QUOTE="aroy, post: 316196, member: 16090"] To understand what a lower ISO will do (and what the "LO" range will not, here is a simplified version of how a sensor works. . The digital sensor works by accumulating photons. The number of photons is limited by its design. The maximum number of photons that a sensel can hold is called the full well capacity, and that defines the base ISO. . There are various types of noise involved in the chain - random, thermal and electrical. For this post I will consider only the noise generated in the sensel. . The Dynamic Range (DR) of a sensel is roughly the ratio of the signal at full well capacity to the noise. . To increase the ISO, you just amplify the signal from the sensel, and that amplifies the noise also. That is why the best DR is at base ISO, as above that the signal decreases while the noise remains more or less same. If you decrease the signal to simulate lower ISO, you will decrease the noise generated in the sensel, but then other noise components generated further down the stream will increase. . After the signal from the sensel is processed it is digitized in an A-D converter. The number of bits in the output is decided on the basis of the speed of conversion and the number of photons in full well. The larger the number of bits in an A-D converter the slower it gets. 16 bits means 64K discrete levels and 14 bits 16K discrete levels. If the full well capacity is less than the number of discrete levels then there is no use having so many levels. The noise (and DR) further reduce the number of levels. . Initial sensors had only one A-D converter, so that the process was very slow, as it converted every bit serially. Modern cameras have one A-D converter per row/column as the design may be, hence are much faster. . The total burst rate of a camera is dependent on - exposure time, including shutter cycling - Read time for all sensels - A-D conversion - Demosaicing - Writing to memory - clearing the sensor of its charge - initializing it to zero Thus a fast A-D and a fast processor are required for fast burst rate. That is one of the reasons that very fast burst rates are limited to 16/18MP sensors. doubling the burst rate from 5fps to 10fps will require the whole chain to be twice as fast. Similarly expanding the sensor from 16MP to 24MP will need 50% faster and from 16MP to 36MP 2.25 faster. Lower ISO. To lower the base ISO you have to redesign the sensor for lower ISO (larger full well capacity, etc), which will mean lower MP. Now unless you can up the DR proportionately, there will be no takers for lower ISO. Majority of the DSLR users are either sports, event shooters & press (high burst rate) or cost conscious users (lower the cost the better) or advanced amateurs (high end equipment with general interest). A lower ISO with enhanced DR will not appeal to any. Lower ISO high DR is available with Medium Format, but the costs are 10-40 times that of the current 35mm DSLR, used by those who want excellent DR with great tonality as well as modularity - fashion & advertising requiring large product images and landscape photographers who want to print large. Because of better DR the tonal gradation in medium format is better compared to 35mm. [/QUOTE]
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Manually lowering the ISO speed (<100)
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