What Is Dual Base Iso
Norine Wiltshire
To perform operations with a vector, we must have a straightforward method of calculating its components. In a Cartesian frame the necessary operation is the dot product of the vector and the base vector.[1] For example,
The dual of an infinite-dimensional space has greater dimension (this being a greater infinite cardinality) than the original space has, and thus these cannot have a basis with the same indexing set. However, a dual set of vectors exists, which defines a subspace of the dual isomorphic to the original space. Further, for topological vector spaces, a continuous dual space can be defined, in which case a dual basis may exist.
In 3-dimensional Euclidean space, for a given basis e 1 , e 2 , e 3 \displaystyle \\mathbf e _1,\mathbf e _2,\mathbf e _3\ , the biorthogonal (dual) basis e 1 , e 2 , e 3 \displaystyle \\mathbf e ^1,\mathbf e ^2,\mathbf e ^3\ can be found by formulas below:
So, when you are shooting with S-Log or with raw you will almost always want to operate the camera at its base ISO in order to maximize the dynamic range that can be recorded and to record with the lowest possible amount of noise and grain.
But what if we could do some magic? What if we could find a way to have more than one base ISO? What if we could operate the sensor at two different sensitivity levels without significantly changing the noise levels or dynamic range? This is what dual ISO brings.
The Sony VENICE and FX9 cameras have a Dual Base ISO function that provides two distinctly different base sensitivity levels. The low and high sensitivity levels have almost exactly the same noise levels and both have the same dynamic range.
Given a vector space \(V\), we define its dual space \(V^*\) to be the set of all linear transformations \(\varphi: V \to \mathbbF\). The \(\varphi\) is called a linear functional. In other words, \(\varphi\) is something that accepts a vector \(v \in V\) as input and spits out an element of \(\mathbbF\) (lets just assume that \(\mathbbF = \mathbbR\), meaning that it spits out a real number). If you take all the possible (linear) ways that a \(\varphi\) can eat such vectors and produce real numbers, you get \(V^*\).
Therefore the dual basis \(b^*\) is equal to \(\ \varphi_1, \varphi_2 \ = \ -x + 3y, x - 2y\\). Now here comes the magic. Suppose that you have a function \(\varphi = 8x - 7y\) and you would like to write it as a linear combination of the dual basis. How would you do?
Recall that the dual of space is a vector space on its own right, since the linear functionals \(\varphi\) satisfy the axioms of a vector space. But if \(V^*\) is a vector space, then it is perfectly legitimate to think of its dual space, just like we do with any other vector space. This might feel too recursive, but hold on. The double dual space is \((V^*)^* = V^**\) and is the set of all linear transformations \(\varphi: V^* \to \mathbbF\).
When we defined \(V^*\) from \(V\) we did so by picking a special basis (the dual basis), therefore the isomorphism from \(V\) to \(V^*\) is not canonical. It turns out that the isomorphism between the initial vetor space \(V\) and its double dual, \(V^**\), is canonical as we shall see right away. Let \(v \in V, \varphi \in V^*\) and \(\hatv \in V^**\). We can now define a linear map:
This also happens to explain intuitively some facts. For instance, the fact that there is no canonical isomorphism between a vectorspace and its dual can then be seen as a consequence of the fact that rulers need scaling, and there is no canonical way to provideone scaling for space. However, if we were to measure the measure-instruments, how could we proceed? Is there a canonical way to doso? Well, if we want to measure our measures, why not measure them by how they act on what they are supposed to measure? We need nobases for that. This justifies intuitively why there is a natural embedding of the space on its bidual. (Note, however, that thisfails to justify why it is an isomorphism in the finite-dimensional case).
And then let us define its dual space \(b^* = \left\ \mathrmd x^1, \mathrmd x^2,\ldots, \mathrmd x^n\right\\). By definition the functionals \(\mathrmd x^i\) must fulfill the following relations:
On Sony Venice, the FX9 and the FX30 the sensors used have two different operating modes that deliver 2 distinctly different sensitivities to light. In each mode the sensors retain almost identical levels of noise and dynamic range. This allows a film maker using these cameras to be able to switch between either of the dual base ISO's according to the light levels they are working under and achieve near identical results with either (there is generaly just a touch more noise at the higher level). The gap between the upper and lower base ISO tends to be between 2 and 3 stops depending on the camera you are using.
Sony's FX3 and FX6 cameras have a slightly different approach where the camera offers 2 distinctly different base sensitivity ranges, Sony don't refer to this as Dual Base ISO but instead call it dual sensitivity. I'm not exactly sure of how this is achieved, but it is likely a combination of adjustments to the way the sensor operates, it's gain and the processing applied to the sensor output. What it delivers is two different sensitivity ranges with a 4 stop gap between the upper and lower range.
Unlike dual base ISO there is a noticable difference in the noise between these two sensitivity levels, but the noise difference is nowhere near as large as it would be if you started at 800 ISO and added a whopping 24dB of gain to get up to 12,800 ISO. There is also a small reduction to the dynamic range at the upper base ISO.
So, is one better than the other? Well, it depends on what you need. If you need a camera to shoot in extremely low light then the dual sensitivity mode of the FX3 and FX6 means you can get some remakable performance in very low light levels. But if you are shooting a drama, performance or similar sometimes the 12,800 ISO from an FX3 or FX6 will be a bit too noisy or simply more sensitivity than you really need, so you might end up shooting at 3200 or 6400 EI which will result in much less noise but will reduce your highlight range. For this kind of application Venice or the FX9 with it's dual base ISO system might be better.
The new FX30 has a dual base ISO sensor and this needs to be considered when comparing low light performance simply by looking at the specifications. On paper it may appear that the FX3 with its upper high base sensitivity of 12,800 will always perform significantly better than the FX30 where the upper base ISO is 2500. But the FX30 at 2500 produces a very low noise image while the FX3 at 12,800 is more noisy. The reality is that while the FX3 and FX6 will remain the better choice for extreme low light the FX30 really isn't that far behind and performs very well in low light.
Illuminating breakdown. Thank you! I added an FX30 to my kit and have been treating it like the FX3 in low light, without fully understanding why it was performing differently. I'm going to take a different approach that keeps the FX30 with the low noise at ISO 2500 more in mind.
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The main advantage of organic transistors with dual gates/bases is that the threshold voltages can be set as a function of the applied second gate/base bias, which is crucial for the application in logic gates and integrated circuits. However, incorporating a dual gate/base structure into an ultra-short channel vertical architecture represents a substantial challenge. Here, we realize a device concept of vertical organic permeable dual-base transistors, where the dual base electrodes can be used to tune the threshold voltages and change the on-currents. The detailed operation mechanisms are investigated by calibrated TCAD simulations. Finally, power-efficient logic circuits, e.g. inverter, NAND/AND computation functions are demonstrated with one single device operating at supply voltages of
Organic thin-film transistors (OTFTs) can be applied for flat-panel displays1,2,3,4,5, radio frequency identification tags6, and sensor arrays7,8 owing to their excellent properties for realizing flexible, large-area electronic devices9,10,11. Organic-transistor integrated circuits for driving paper-like displays and large-area sensors have been commercially manufactured in the last decades12,13. Despite these advances of organic transistors, one of the major remaining issues on organic-transistor integrated circuits is the control of their threshold voltages (Vth)14,15, i.e., the gate bias at which the transistor switches between the high current accumulation regime and the low current depletion regime. The Vth control is crucial for the design and manufacture of complicated integrated circuits. For logic gates, the Vth determines the trip point, which is the input bias at which the gate inverts the output signal16. For sensing applications, the Vth signifies the bias at which the largest change in current occurs, i.e., the point of the highest sensitivity17,18. Although there are reports in which the Vth of organic transistors is changed by the chemical channel doping of the organic semiconductors replacing the covalently bonded silane layers bearing sulfonic acid groups19 and by modifying the surface of the gate dielectric layers20,21, such approaches are still far from practical use due to the limited reliability of the manufacturing process.
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