Why does a smaller aperture size have a high depth of field? What is the physics behind this?
There are several questions here about , about , and about . And of course there's the basic . And plenty of  questions. There's related questions like . But there's no be-all-end-all question asking:  What exactly determines depth of field in a photograph?   Is it just a property of the lens? Can lenses be designed to give more depth of field for the same aperture and focal length? Does it change with camera sensor size? Does it change with print size? How do those last two relate?
How can I accept the Microsoft EULA agreement for ttf-mscorefonts-installer? Allow setuid on shell scripts The setuid permission bit tells Linux to run a program with the effective user id of the owner instead of the executor:  &gt; cat setuid-test.c  #include &lt;stdio.h&gt; #include &lt;unistd.h&gt;  int main(int argc, char** argv) {     printf("%d", geteuid());     return 0; }  &gt; gcc -o setuid-test setuid-test.c &gt; ./setuid-test  1000  &gt; sudo chown nobody ./setuid-test; sudo chmod +s ./setuid-test &gt; ./setuid-test  65534   However, this only applies to executables; shell scripts ignore the setuid bit:  &gt; cat setuid-test2  #!/bin/bash id -u  &gt; ./setuid-test2  1000  &gt; sudo chown nobody ./setuid-test2; sudo chmod +s ./setuid-test2 &gt; ./setuid-test2  1000     Wikipedia :     Due to the increased likelihood of security flaws, many operating systems ignore the setuid attribute when applied to executable shell scripts.   Assuming I'm willing to accept those risks, is there any way to tell Linux to treat the setuid bit the same on shell scripts as it does on executables?  If not, is there a common workaround for this problem? My current solution is to add a sudoers entry to allow ALL to run a given script as the user I want it run as, with NOPASSWD to avoid the password prompt. The main downsides to that is the need for a sudoers entry every time I want to do this, and the need for the caller to sudo some-script instead of just some-script How to boot from iso with Grub2/Burg boot loader I'm using Ubuntu as my primary OS and alternative is Windows 7 for gaming, and another stuffs. I want to have menu to boot some live CD ISO. Is there anyway to make menu entry in Grub2/Burg to boot ISO file like the CD way?  I see there are some ways to make it possible but almost method need specified boot arguments (kernel parameters). But I have mixed kind of Live OS wan to boot up using boot loader included: Linux, Unix, DOS (for recovery purpose)...   I'm looking for more generic way to make it easy to discover and add to the menu config file. Serving wp-includes (front-end) javascript from a different domain? The WordPress Codex points to an extremely simple way to change the URL of the wp-content directory, which is, adding this in wp-config.php:  define( 'WP_CONTENT_URL', 'http://example.com/wp-content');   And that does the job of serving most of the JavaScript and CSS files on my website from the different domain, except two.  http://mywebsite.com/wp-includes/js/comment-reply.js http://mywebsite.com/wp-includes/js/quicktags.js   The reason is very clear — these JavaScript files are served from within the wp-includes directory, which is not affected by the aforementioned rule.  So, is there a similar or simple method to have them served from example.com i.e. the domain of my choice? or is unregistering and enqueuing the scripts from a custom URL (done in functions.php) the only way? How to unit test an object with database queries I've heard that unit testing is "totally awesome", "really cool" and "all manner of good things" but 70% or more of my files involve database access (some read and some write) and I'm not sure how to write a unit test for these files.  I'm using PHP and Python but I think it's a question that applies to most/all languages that use database access. Question about Subrings and integraly closed Prove that $Y=-2\sum_{i=1}^n \ln F_{X_i}(X_i)$ have distribution $\chi^2(2n)$ I could have modifications ready for a specific question that was downvoted. I felt like the best thing to do was to delete the post first.  Is it possible to flag for moderator attention after you deleted the post ? What is the best practice re: API Version of your Apex Classes? I'm in the process of pushing some updates to some code I originally wrote 12-18 months ago, and the API Version is between 27.0 and 29.0  I know this is to protect the integrity of the test classes you've built (in case they have changed some things) but is there a best practice around either leaving these alone or trying to keep them up-to-date (maybe just once a year instead of at each release)? Why doesn't Ubuntu 16.04 in Windows have ubuntu.exe? Illustrator CS5 brick pattern with perspective I created a curving arrow shape that starts wide at the bottom and thins out near the top where the point is. I also created a brick pattern swatch but when I apply it to the shape it appears like the pattern is overlaid instead of like a real road where the bricks follow the shape and narrows near the most distant point. How can I apply a perspective to the brick pattern without looking like I used a clipping mask?  Here is a link to what I achieved with a clipping mask - not what I want though. I need the bricks to look like they are inlaid just like in real life. How is the value of $\pi$ ( Pi ) actually calculated? When I was a child I was taught $\pi$ (Circumference/Diameter) is an irrational number  and can be approximated to $22/7$ but $= 3.(142857)(\ldots)$.      But where does this value comes from?  In short How do I derive $\pi$? How to close ports / disable services? I just portscanned my system with nmap and got the following result:  PORT    STATE SERVICE 25/tcp  open  smtp 631/tcp open  ipp   what are these services and how i do disable them? probably i don't need them. Uploading video to youtube in right format Evaluating $\zeta(0)$ using the functional equation of Riemann-Zeta function. $$\zeta(it)=2it\pi it−1\sin(i\pi t/2)\Gamma(1−it)\zeta(1−it).$$ Everything on the RHS is never zero,  Does that means LHS has no zeros, since $\sin(s)$ has a simple zero at $s=0$ while $\zeta(1−s)$ has a simple pole at $s=0$  (the Laurent expansion), so the product $\sin(i\pi t/2)\zeta(1−it)$ is finite and nonzero at $t=0$.  My question is that from functional equation one can't get direct answer $\zeta(0)=−1/2$ unless using alternate infinite series ! With the new  and the upcoming release of  film, JK Rowling has been awesome and given us new writing on the .  In the introduction it is stated that there are eleven established/registered schools. There are writings for six of them. I don't think we need a new writing for Hogwarts... so that means seven have been located and defined.   Hogwarts School of Witchcraft and Wizardry - Great Britain  - France  - Northern Europe (possibly Estonia, Latvia, or Belarus)  - Japan  - Africa (possibly Congo/DRC)  - Brazil  - United States   Do we know anything of possible location or names of the other four schools? I know Koldovstoretz was mentioned as school in Russia, but is that still canon?   Koldovstoretz - Russia (maybe depending on current canon)   The final three are my guesses based on the population and geography on the world.   Name Unknown - China (based on population) Name Unknown - India (based on population) Name Unknown - Australia (based on geography)   Related: I am Haitian, and traveling with a Haitian passport. I have to go to London with a work permit (tier 2 visa) on the 29th of July but I have 2 hour transit in Dublin.  Do I need a transit visa? Can I get it at the airport?  I also have a valid US visa. More Question Filtering options I realize that this may be a big request, but...  I think that instead of tabs on the recent question activity pages, or more likely as a new tab, adding a more advanced filtering option.  For instance, being allowed to exclude tags, filter by accepted answers or not, and, most importantly, being able to combine multiple filters!  E.g.: Filtering posts with tag Javascript without tags Jquery and AngularJS with no accepted answers and a score >= 0.  I feel like this is a biggish change that, if implemented as a new tab, wouldn't be that hard to implement, but would be very useful. How many ways can $r$ nonconsecutive integers be chosen from the first $n$ integers? What is a complete list of the usual assumptions for linear regression?