The F number is a ratio calculated purely from the focal length of the lens and the size of the aperture. Any light meter talks in terms of F, Shutter, and ISO.   Different glass, or just different number of elements, is going to change the number of photons that get though the lens; we compensate for ND filters by adjusting F. What am I missing? Why aren't  part of exposure calculations?  In other words, I know what T numbers are, and how they differ from F-stops. What I don't know is why handheld light meters and related tools have no provision to take T into account, but talk only in terms of F.
seem to be well-regarded for their versatility and accuracy of metering.  What puzzles me about them is how can they account for the different light transmittance of different lenses? It's easy for an in-camera metering system that meters  so any peculiarity in transmittance is already applied to light when it reaches the metering sensor. But a standalone meter does not have the privilege of looking at the world through the lens it meters for. I tried looking it up in  and , but this issue was not touched upon at all.  This leaves several variants how it could be handled -   light meter uses  for aperture display/input, and photographer is expected to perform the adjustments to and from  (which are used by cameras); light meter assumes some median transmittance of lenses of its era, and automatically accounts for that; photographers simply ignore the matter - even a 75% transmitting lens will be off only by about half a stop, no big deal; each light meter used is expected to know that you have to dial in some exposure compensation to account for the light loss; ...   So how does it work in real world?
Unable to uninstall Universal Apps through PowerShell A number of times I have encountered in text-books and articles that neutrinos might contribute only a small fraction to dark matter. The reason has to do with the fact that if all of the dark matter consisted of neutrinos, then small-scale structures in the Universe could not have formed yet, because, as they say, neutrinos "wash out" small fluctuations. However, none of these texts provided a reference to any specific sources explaining in detail what is meant by "washing out". After all, neutrinos are notorious in their weak interaction with baryonic matter, so if there is a small-scale fluctuation of baryons, then how background neutrinos can prevent it from growing further if they practically do not interact with baryons? I guess the question boils down to calculating cross-sections of interactions at specific temperatures. I would appreciate comments and references to sources addressing this particular issue. I lost my .keystore file? Responding to your "too localized" concerns Finding largest file recursively I am trying to find the largest file in a directory recursively. If there is a subdirectory inside of that directory the function needs to go inside that directory and check to see if the largest file is there. Once the largest file is found the output is displayed with the relative path name and the name and size of the largest file.  EX:  dude@shell2 (~...assignment/solutions) % bash maxfile.sh ~/test class/asn dude.h.gch: 9481628   This is what I have:  #!/bin/sh clear  recursiveS() {     for d in *; do         if [ -d $d ]; then             (cd $d; echo $(pwd)/$line; du -a; recursiveS;)         fi     done } recursiveS   I have been stuck for a while now. I cannot implement this by pipelining a number of existing Unix tools. Any ideas would be nice! I understand the whole concept of Rencontres numbers but I can't understand how to prove this equation  $$D_{n,0}=\left[\frac{n!}{e}\right]$$  where $[\cdot]$ denotes the rounding function (i.e., $[x]$ is the integer nearest to $x$). This equation that I wrote comes from solving the following recursion, but I don't understand how exactly the author calculated this recursion.  $$\begin {align*}  D_{n+2,0} &amp; =(n+1)(D_{n+1,0}+D_{n,0}) \\ D_{0,0} &amp; = 1 \\ D_{1,0} &amp; = 0  \end {align*} $$ Got this problem from a friend and would like some pointers if anyone has any.  Fill an $n \times n$ matrix with the symbols $\{a,b,c,d\}$ subject to the following:     Only the symbol $a$ appears to the left or above an $a$    Only the symbol $b$ appears to the right or above a $b$    Only the symbol $c$ appears to the left or below a $c$    Only the symbol $d$ appears to the right or below a $d$     Here are some examples of a valid fillings: $$\left( \begin{matrix} a &amp; a &amp; b  &amp; b \\ a &amp; a &amp; b &amp; b \\ c &amp; c &amp; c &amp; d \\  c &amp; c &amp; c &amp; d  \end{matrix}\right) $$  $$\left( \begin{matrix} a &amp; a &amp; a  &amp; a &amp; a &amp; b  &amp; b \\ a &amp; a &amp; a  &amp; a &amp; a &amp; b  &amp; b \\ a &amp; a &amp; a &amp; d &amp; d &amp; d &amp; d \\  a &amp; a &amp; a &amp; d &amp; d &amp; d &amp; d\\a &amp; a &amp; d &amp; d &amp; d &amp; d &amp; d\\c &amp; c &amp; d &amp; d &amp; d &amp; d &amp; d\\  c &amp; c &amp; d &amp; d &amp; d &amp; d &amp; d  \end{matrix} \right) $$  What I have done: We'll it is clear to me that the $a$'s (for example) make up a sort of Young Diagram just by the property above. But there is more to the problem than that. If your YT for $a$ is just a square, then you might have a reversed (right justified) YT available to place for the $b$'s. Details like this seem to make this a tricky problem for me. I am intrigued by this problem and I just thought I'd share it here in case there is some easy way to do this counting problem that I've never heard of.  Thanks, Identify a book with a social engineering theme I originally read this book in the mid- to late '70s.   The premise was a bureaucracy whose job it was to manipulate events in human history by making the smallest possible change that would effect the desired outcome. Not time cops in the sense of going after law breakers.  The intent was to maintain a policy of non-interference as much as possible but when interference was warranted then to make the least possible change and to do so invisibly.  For example, they might take someone's keys off the dresser and put them just out of sight underneath the dresser where they plausibly might have fallen.  The subject would never know of the manipulation but would then be delayed getting out of the house and the ripples grew from there to avert a war or otherwise affect events on a large scale.  After reading that, whenever I would lose something - especially in an improbable way such as dropping a screw at my feet and then finding it on the other side of the room half an hour later - I would take some consolation in the thought that I had just averted some global catastrophe.  I was pretty scatterbrained as a kid (we call that ADHD nowadays) so I experienced this a lot.  Given that I've spent so much time pondering the ideas from the book, I'd love to re-read it. Prove using induction that from a set of $n+1$ numbers from $\{1,2,..2n\}$, at least one number will evenly divide another. Given a set of $n+1$ numbers out of the first $2n$ natural numbers, $\{1,2,\ldots,2n\}$, prove that there are two numbers in the set, one of which divides the other.  I can't tell if I'm reducing the problem in the right way.  Would it be something like:  Induction Hypothesis: A set of $n+1$ numbers from the first $2n$ natural numbers contains two numbers, one of which evenly divides the other.  Base Case: $n=1$, $\{1,2\}$, 2 is divisible by 1.  Consider a set of $n+2$ numbers, $A$, from the first $2n+2$ natural numbers. There are three cases:   Each number in $A$ is less than or equal to $2n$.  The proof follows from the induction hypothesis. One number in $A$ is greater than $2n$.  The remaining set of $n+1$ numbers must each be less than or equal to $2n$.  The proof follows from the induction hypothesis. $A$ contains both $2n+1$ and $2n+2$. I'm not sure how to solve this case.   I'm working through Udi Manber's Introduction To Algorithms: A Creative Approach for personal development, so in keeping with the spirit of the book, I'm trying to use induction.  Without induction, the question is identical to This is a question from Stromberg related to Steinhaus' Theorem:     If $A$ is a set of positive Lebesgue measure, show that $A + A$ contains an interval.   I can't quite see how to modify the Steinhaus proof though. Windows 10, 'System' process taking massive amounts of RAM Since I upgraded to Windows 10, my system has been consuming RAM excessively    I've been reading a bit and determined it's likely a driver leaking memory. So I got myself the Windows Driver Kit and tracked memory usage with poolmon:    However, I don't really know how to proceed from here. Is the item tagged "smNp" the culprit in this issue? How do I go from there to actually identifying the driver?  I tried some stuff like "C:\Windows\System32\drivers>findstr /s smnp ." but it returned no results. I also took a look at the pooltag.txt file and this is the description I found for it:      So yeah, any help would be appreciated. Thanks in advance. I've made a simple snowfall particle simulation (using gandalf3's solution: ). Is there a way to loop the animation, so the transition between last frame and first frame is not visible? Is there a setting to do it? I want to trace a border in a box or minipage like this model. A border customizable in left angle on top and right angle in bottom. Somebody can help me? Thanks a lot JPierre iPhone 5S, LTE does not work How do you make Ubuntu accept files sent over bluetooth I have a problem when I send my files from phone to ubuntu 12.04 via bluetooth as the phone prompts with the message "the file not sent"! I can send any files from ubuntu 12.04 to my android phone. Given two points (defined, for instance using nodes), I want to compute the distance between them.   Is there some build in functionality in tikz to do this? If not, how can it be done using the mathematical engine?   The application I have in mind is to draw an circular arc centered at (a) and passing through some second point (b), where only (a) and (b) are known. Sorry for asking such a basic question - but is there an actual term for the numbers that appear before and after the decimal point?  Example:  25.18  I know the 1 is in the tenths position, the 8 is in the hundredths position. are there singular terms which apply to all of the numbers that appear both before and after the decimal point?  I'm building a billing system, storing dollars and cents as integers (in separate columns), but for other currencies "dollars" and "cents" are not the correct terms = ).  Thanks! Why do we use $x - y$ rather than $x + y$ in the definition of the convolution? Is it just convention? (If we are thinking of convolutions as weighted averages, for instance against "good kernels," it should make no difference.)  Why $(f * g) (x) = \int f(y) g(x - y) dy$ rather than $(f * g) (x) = \int f(y) g(x + y) dy$?  Edit: I'm finding it really hard to choose a best answer. There are at least three very good ones here. Cauchy condensation test The following is Cauchy condensation test:  If $b_n \ge 0$ and $b_n \ge b_{n+1}$ then $\sum b_n$ converges if and only if $\sum 2^n b_{2^n}$ converges.  Is the following modified Cauchy condensation test possible:  Let $N \in \mathbb N$. Then if $b_n \ge 0$ and $b_n \ge b_{n+1}$ then $\sum b_n$ converges if and only if $\sum N^n b_{N^n}$ converges? I will soon buy a new iPhone. If I log in with my Apple ID in my new phone could I still access my Clash of Clans village without starting from scratch?