One of my favorite qualities of large apertures (besides the low light capability) is their characteristic shallow focus that can offer dramatic background blur.  I've been considering how a micro format camera such as a micro four-thirds or even something like a Canon G16 or S120 (with 1/1.7" sensor) might perform with regards to depth-of-field. Both of those cameras boast an f/1.8 ratio. I am of the understanding that the lens won't be as fast as an f/1.8 on an APS-C or fullframe sensor as it obviously won't be capturing nearly as much light, but how does depth-of-field scale down?  To clarify my question consider these scenarios:   a camera body with a fullframe sensor and an appropriately matching f/1.8 lens a camera body with a micro 4/3 sensor and an appropriately matching f/1.8 lens a camera body with a 1/1.7" sensor and an appropriately matching f/1.8 lens   How would the depth-of-field compare? Let's also assume for the sake of argument, that all lenses have focal lengths that correspond to the same field-of-view.
If APS-C and similar crop-sensor digital cameras have a focal length multiplying effect such that a 50mm lens has an apparent focal length closer to the field of view of an 80mm on a full frame camera, and yet at the same time the depth of field for the smaller sensor camera is more like the depth of field a 50mm lens would produce on a full frame camera (using the same aperture), then this would seem to suggest the concept of an "aperture dividing effect."  In other words, a 50mm f/1.8 lens on an APS-C camera would act more like a 80mm f/2.8 (approx. 1.8 * 1.6x) lens in 35mm equivalent — for depth of field, not considering exposure.  Can someone with a better understanding of the physics involved clarify this for me.  I've never seen this concept explicitly mentioned anywhere, so I am a bit suspect of it.
I bought two pieces of land. One from Morthal, and one from Falkreath. Morthal was the first plot of land I purchased. I only finished half of it. I bought the plot of land in falkreath because I liked the nature better. I finished the house completely in Falkreath. Every time I try to adopt a child off the streets it keeps saying "I have a place but no room for you" Even though I have the bedrooms in my Falkreath house. Why can I not adopt a child and have him/her live at my house in Falkreath? Many older movies seem to have vivid reds and particularly realistic or noticeable skin tones (they certainly seem to stand out from typical skin tones on TV or the majority of movies). This applies even in DVD or online versions and is not, given the range of material I've noticed the effect in, an artifact of special post processing or deliberate colour manipulation.  All the movies I've noticed the effect in are from the film era, especially from when colour became common to the late 1960's. I used to think it was just Technicolor but I've seen things recently that don't claim to be Technicolor that also show the effect.   claims the effect was due to the final print being constructed late in the process for separate black and white film strips for each primary colour allowing the final dyes to be very vivid and clear:     The rich colors that the Technicolor process gave came in part from the fact that the color was not added to the process until the final stages. The color information was recorded and processed as separate black and white images which were relatively easy to control and preserve.   Is this a good explanation? "Welcome to emergency mode!" Think it is a fsck problem My computer booted to a black screen with this error message.  Welcome to emergency mode! After logging in,type "journalctl -xb" to view    system logs, "systemctl reboot" to reboot, "systemctl default" or ^D to    try again to boot into default mode.   journalctl -xb snippet (what I think is wrong):  -- Unit systemd-fsckd.service has begun starting up. juli 09 15:40:16 kim-SSD-Sationary systemd-fsck[414]: /dev/sdb1 contains a file system with errors, check forced. juli 09 15:40:16 kim-SSD-Sationary systemd-fsck[414]: /dev/sdb1: Inodes that were part of a corrupted orphan linked list found. juli 09 15:40:16 kim-SSD-Sationary systemd-fsck[414]: /dev/sdb1: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY. juli 09 15:40:16 kim-SSD-Sationary systemd-fsck[414]: (i.e., without -a or -p options) juli 09 15:40:16 kim-SSD-Sationary systemd-fsck[414]: fsck failed with error code 4. juli 09 15:40:16 kim-SSD-Sationary systemd-fsck[414]: Running request emergency.target/start/replace juli 09 15:40:16 kim-SSD-Sationary systemd[1]: systemd-fsck-root.service: main process exited, code=exited, status=1/FAILURE juli 09 15:40:16 kim-SSD-Sationary systemd[1]: Failed to start File System Check on Root Device. -- Subject: Unit systemd-fsck-root.service has failed -- Defined-By: systemd -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel --  -- Unit systemd-fsck-root.service has failed. --  -- The result is failed. juli 09 15:40:16 kim-SSD-Sationary systemd[1]: Unit systemd-fsck-root.service entered failed state. juli 09 15:40:16 kim-SSD-Sationary systemd[1]: systemd-fsck-root.service failed. juli 09 15:40:16 kim-SSD-Sationary systemd[1]: Starting Remount Root and Kernel File Systems... -- Subject: Unit systemd-remount-fs.service has begun start-up -- Defined-By: systemd -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel   I ignored other errors like: ACPI PCC probe failed, nvidia not proprietary, etc.  I can access my PC by pressing Ctrl+D , but it is annoying. What characters are allowed for the display name? I tried editing my display name and for some names it gives me this error:     Display Name can only contain a-z, 0-9, spaces, apostrophes or hyphens and must start with a letter or number   That is clearly not the case, because it will take the following names:   NullUserException -龍- NullUserException Ω    NullUserException ఠ_ఠ NullUserException ಠ_ಠ NullUserException இ_இ   But it won't let me do:   NullUserException  (╯°o°)╯ NullUserException ٩๏̯͡๏)۶ NullUserException ☜(ﾟヮﾟ☜) NullUserException อ้_อ้   So what's the regex used (assuming that's what's being used), so I can try out allowed names without actually changing it? Total width of element (including padding and border) in jQuery As in the subject, how can one get the total width of an element, including its border and padding, using jQuery?  I've got the jQuery dimensions plugin, and running .width() on my 760px-wide, 10px padding DIV returns 760.  Perhaps I'm doing something wrong, but if my element manifests itself as 780 pixels wide and Firebug tells me that there's 10px padding on it, but calling .width() only gives 760, I'd be hard pressed to see how.  Thanks for any suggestions. Types of circular acceleration? To my knowledge there are three types of acceleration when a body (e.g. a rod) is moving in a circle about an axis. These are:   Angular acceleration : this is the rate of change of angular velocity. Tangential acceleration : this is the linear acceleration of the system in a tangential direction to the circle and equals the radius times the angular acceleration. Radial/centripetal acceleration : this is the linear acceleration of the system that is directed inwards towards the center of the circle.   I also think there are two types of velocity:   Linear velocity: this is its velocity in the tangential direction and is constantly changing Angular velocity or angular frequency: this is the rate of change of angle.   Is the above correct? And have I missed anything? Logic soundness and completeness I have to do a number of similar type questions, but I am having trouble grasping the general concepts around soundness and completeness. I have read up on the general definitions and think I understand them, but when asked to show something like the following I come up blank. Thanks for any ideas/help.   Show that the following propositional proof system, PCa, is sound but not complete.  PCa  Connectives (and constants) ∨, ∧, →, ↔, ¬, 0, 1  Axioms All tautologies of the form F→F  Rules of inference Hypothetical Syllogism How do I inspect the view hierarchy in iOS? I have a very simple question that can be stated without proof. Are all eigenvectors, of any matrix, always orthogonal? I am trying to understand Principal components and it is cruucial for me to see the basis of eigenvectors. How to install qt 4.8 from repository? How to install qt 4.8 and QtCreator from repository ? The shrine indicator (shrine detector? GPShrine?) has both visual and audio cues, so when I'm near a shrine, it beeps constantly. Unfortunately, I occasionally play the game near other humans who are engaged in their own activities, and my wife is decidedly unimpressed with this feature.   When I got the shrine indicator, I could have sworn that the dialogue said I could press [Y] to disable it... but pressing Y pulls out my weapon.   Ideally, I'd like to just make it stop beeping, but stay on for visual cues. But I'll settle for being able to turn it off entirely at times. So I was thinking about something for the past while  Consider a large spherical foam-ball with homogeneous density. Where a foam ball is defined as an object that can absorb matter with 0 friction (example: a gravitational well without an object inside). This is a purely theoretical construct.  If the foam-ball has a radius R and a charge Q. What charge must the foam-ball have, such that there is well defined sphere or horizon such that any object with a negative charge (even if it is the slightest bit) must travel faster than C in order to escape the field of the ball.  Aka what charge would turn this into a black-hole for all objects with opposite sign on their charge?  Once again I assume the foam-ball is a single particle, that doesn't repel itself... its just a very large homogenous 'thing' with charge. Make it clearer when looking at a question if I've already voted to close it Since "" we now have the possibility to retract close votes.   However, as mentioned in "" there is no indication when looking at a question to see if I have already cast such a close vote.  Therefore, could we have a UI improvement to show this? Adding some image with freehand circles to improve visibility. Is an empty set equal to another empty set? I have a definition that claims that two sets are equal A = B, if and only if:  $\forall x ( x \in A \leftrightarrow x \in B)$  An empty set contains no elements. If I define the sets:  A = $\emptyset$  B = $\emptyset$  then can I conclude that A $\neq$ B? Since they contain no elements? Or would I have to show that an elements exists in one but not the other? To me it seems that these are not equal, but I'm struggling to wrap my head around this.  Thanks, Paul I'm designing a small module that breaks out a DIP SPI EEPROM to a 2x5 pin header socket(more info here: ). I want to mount the socket on the end of the board, with the pins lying parallel to the board.  I think two 5x1 surface-mount header footprints, on both sides of the board right near the end would do the job. Trouble is, KiCAD doesn't come with such a footprint(if it does, I haven't found it yet). Where might I find one? If one doesn't exist, that's OK; I'll have a shot at making my own. I've read  about how some publishers (e.g., Springer) allows authors to submit to arXiv before journal submission, but they make authors wait for a year after acceptance to submit to arXiv.   My question is: Is it okay to submit to arXiv during the time when the paper is under consideration by the journal, for example after it has been "revised and resubmitted" but before final decision? Kepler problem in time: how do two gravitationally attracted particles move? Two particles with initial positions and velocities $r_1,v_1$ and $r_2,v_2$ are interacting by the inverse square law (with G=1), so that  $$ {d^2r_1\over dt^2} = - { m_2(r_1-r_2)\over |r_1-r_2|^3} $$ $$ {d^2r_2\over dt^2} = - { m_1(r_2-r_1)\over |r_1-r_2|^3} $$  (the inverse square law along the line of separation). What is the complete solution of these differential equations? What is the position of the two objects as a function of time?  After reading a lot on Wikipedia, I've come to the definition of center of mass and relative coordinates:   $$R(t) ~=~ \frac{m_1 r_1 + m_2 r_2}{m_1+m_2}$$  $$\ddot{r}(t) r(t)^2 ~=~ (m_1+m_2)G$$  Where $R$ is the center of mass, and $r$ is the displacement between the particles... Is this correct? How do I proceed to solve the differential equation? Where To start Learning With Salesforce Development Where should I start learning? There are various topics to learn like Objects, Classes, Apex, Visualforce, SOSL, SOQL, Triggers, etc. There are so many options out there to start learning. I couldn't decide what topic to learn first, and then step by step get proficiency in all aspects of Saleforce. Is gcc 4.8 or earlier buggy about regular expressions? What is the difference between $Q=\Delta U+W$ and $\Delta U=Q+W$?