How would I alter some rectangles to follow an existing curve
How to create this curved 90-degree-angle quickly
The more I read about this, the more confused I become. Illuminance, as I understand it,  measured in lux, is the perceived brightness of light on a surface. It's what you'd measure with an incident light sensor. Luminance, then, is how much reflected light you'd perceive looking at that surface. This is what the light meter in a camera measures. Am I correct so far?  In both cases, the word "perceived" is important, because the scales are weighted using a  to map wavelengths to . However, in the case of illuminance, there's only actual perception if your eye happens to be the surface in question.  I can basically grasp this, but then I come across charts saying things like "family living room: 50 lux". Wait, hold on! Does that really mean that the typical lights in a house are that bright, or is it just confused and wrong, or am I confused and wrong?  If you're not taking pictures of light sources directly, why would an incident light meter reading ever be useful in photography? Reflected light recorded on film or by a sensor is usually what makes a photograph. So, if I have an incident light meter, how does that reading relate meaningfully to my camera settings?  Since incident light meters are sold and used, this implies that there must be some useful conversion. But this is where my brain explodes. Google tells me that 1 lumen equals 1 candela, so therefore 1 lumen/m² (i.e. 1 lux) must equal 1 candela/m2 (i.e. 1 nit). But clearly something is missing from this. There's something called a "steradian". Cones are involved. I'd never heard of this before; how does it fit in? I can see how it might be determined when calculating the usefulness of LED home lighting, but for a photo, I'm at a loss.  Some part of my (exploded, from the last paragraph) brain is trying to relate this to the difference between flash metering with TTL and with an incident meter. But how can the incident meter work without knowing the reflectance properties of the objects in the scene? Is this what the "C" in the  is all about? Is it just an average-this-probably-will-work value, or is there more to it than that? And if it is just an average, what knowledge is necessary for compensating for off-averages scenes? (As with the , where the photographer simply judges if the scene should be rendered brighter or darker than the average given by the meter.)  So yeah, so much confusion. In short:   What's the difference? Can one meaningfully convert between the two? When and how are illuminance / incident light measurements useful for photography?     Update: I appreciate Stan's answer, which covers the third point of when and how pretty well. And I think I've basically got the first point figured out, as described above. But I'd appreciate some answers covering the issue of conversion as well, both in the mathematical abstract and as the practical for photography. And I wouldn't mind more why and how, either. Intuitive/direct proof that a rectangle partitioned into rectangles each with at least one integer side must itself have an integer side A challenge problem asked to show that if rectangle $R$ with axis-parallel sides is partitioned into finitely many subrectangles $R_1,R_2,\ldots,R_n$ (also with axis-parallel sides), such that each $R_i$ has at least one integer side length, then $R$ must also have at least one integer side length. The only proof I've seen, although simple, is quite unintuitive. Namely you look at the integral  $$ \int_R e^{2 \pi i (x+y)} dx dy $$ and note that the integral is $0$ if and only if $R$ has an integer side length, and then note that by assumption the integral is $0$ over all the $R_i$, hence summing the integral over all $R_i$ gives that the integral is also $0$ over $R$. Can someone give a more direct/intuitive argument that doesn't use voodoo like a complex-valued integral? How can I make Windows Paint save by default as JPEG format? Researching English/Christian families in India during first half of 19th century? How to make `man` work for shell builtin commands and keywords? What is the difference between Early and Late Binding? What is the difference between early and late binding? How does ServerName and ServerAlias work? It's the following part of a virtual host config that I need further clarification on:  &lt;VirtualHost *:80&gt;   # Admin email, Server Name (domain name), and any aliases   ServerAdmin example@example.com   ServerName  141.29.495.999   ServerAlias example.com ...   This is and example config, similar to what I currently have (I don't have a domain name at the moment).  &lt;VirtualHost *:80&gt; - Allow the following settings for all HTTP requests made on port 80 to IPs that this server can be contacted on. For instance, if the server could be accessed on more than one IP, you could restrict this directive to just one instead of both.  ServerName - If the host part of the HTTP request matches this name, then allow the request. Normally this would be a domain name that maps to an IP, but in this case the HTTP request host must match this IP.  ServerAlias - Alternate names accepted by the server.  The confusing part for me is, in the above scenario, if I set ServerAlias mytestname.com and then made an HTTP request to mytestname.com, there would have to be a DNS record pointing to the server's IP for this to work? In which case, is ServerAlias just basically EXTRA ServerName entries?  Say I had a DNS entry such that foobar.com = 141.29.495.999 but then I had ServerName = 141.29.495.999 and ServerAlias was empty, would that mean that although foobar.com gets resolved to the right IP, because there is no reference to accept foobar.com in ServerName or ServerAlias?  Or something. Man I'm confused. How does one manually restart graphics drivers? I'm suffering from the dreaded . The problem is intermittent and can be "solved" by putting the computer to sleep or restarting it. I hope simply restarting the graphics drivers will remove the symptoms of the problem.  would seem to indicate that restarting the graphics drivers is possible in Windows 7. My question is: how? Solving "The ObjectContext instance has been disposed and can no longer be used for operations that require a connection" InvalidOperationException Should it be obvious that independent quantum states are composed by taking the tensor product? Prove that $C\exp(x)$ is the only set of functions for which $f(x) = f'(x)$ How to disable automount in nautilus's preferences Return more than 2000 records (SOQL) I'm trying to retrieve a list of Account objects from Salesforce using SOQL. Originally my query was this:  var result = service.query("SELECT Id, Name, RecordTypeId FROM Account"); return result.records.Select(record =&gt; record as Account).ToList();   However this only returns a maximum of 2,000 records and I have over that which I need to be returned by this query. After some digging around I found an example in Java which loops over the SOQL query which will allow a maximum of 10,000 records to be returned. I tried to replicate this in C# but it differs slightly, here is what I have now:  var accounts = new List&lt;Account&gt;(); foreach (Account account in service.query("SELECT Id, Name, Composer_ID__c, RecordTypeId FROM Account").records)     accounts.Add(account);  return accounts;   However this still only returns a maximum of 2,000 records. How can I return more than 2,000 records by querying Account? Why doesn't the last digit method work for divisibility by 4? I wish to explain to a grade 5 kid, the answer to the question - 'When can we know that the observing the last digit of a number will not be sufficient to determine its divisibility by a given N?'  For example - It doesn't work for 3, because we get all sorts of digits, i.e. from 0 to 9, at the units place. The same reason works for 7 and 9.   But what would be a convincing argument for 4 and 8? Even though the last digits form a pattern - 0, 2, 4, 6 and 8 - but we're still not sure about its divisibility. How do you plot time on the X axis in excel? I need to plot the decay of my phone's battery against time over night. My starting time is 23:17:47 and my ending one is 07:05:49. I don't have any issue in changing the time format in the current one, selecting an XY chart and plotting time on the X axis.   The problem arises because Excel doesn't start the X axis at 23:17:47, but instead at 00:00:00, so my first value is drawn from the end of the graph and the goes back at the beginning when time values are over 00:00:00.   In other words, how do I set up the min time value to 23:17:47 and the max to 07:05:49 in excel? Show lim sup (an) = lim inf (an) for increasing for increasing sequence of subsets. How do I programmatically create a new content type? Do resistances stack? If a creature had resistance to spells, and then cast fire resistance on it, would it take only 1/4 damage from all fire spells? Why is logistic regression a linear classifier? Since we are using the logistic function to transform a linear combination of the input into a non-linear output, how can logistic regression be considered a linear classifier?  Linear regression is just like a neural network without the hidden layer, so why are neural networks considered non-linear classifiers and logistic regression is linear? Where are some good places to find royalty free stock images? I'm always on the hunt for free stock images to use while I design, what are some good resources for images that are under a a royalty free or creative commons licence?