I have a Sony RX10 iv and now realize that the 600mm lens is actually just 220mm.  I am looking at the Tamron 70-300mm lens for my Sony a7iii and wondering if the Tamron shoots a full 300mm.
I'm reading that a 50mm lens is recommended as a first prime lens for DSLR owners as it's supposed to give a 'natural' perspective, but when used on (most) DSLRs, the view is cropped, as if you were zoomed in by 1.5-1.6x, so it's more of a telephoto lens when used on a DSLR. I've also read however that the 50mm lens gives the same perspective on a DSLR and a 35mm, and shouldn't really be considered to be 'equivalent' to an 80mm lens as the crop factor isn't really a magic focal length changer.  Can someone explain how the image is different from (for example) a 50mm lens on a DSLR and an 80mm lens (assuming 1.6x crop factor) on a 35mm camera?
How can I use the compositor on the result of the sequencer? I recently ran a renderfarm on a file with some compositing setup, but I forgot to set the composite output back to the Composite node instead of the Viewer I was temporarily using. Since the node setup didn't require anything besides the image data (i.e., no Z-buffer, object IDs, etc.) I figured that I could just run the compositor on each frame individually. However, this proved to be somewhwat difficult.  It seems that the sequencer is run after the compositor (despite their non-exclusivity in the Post Processing panel), so my idea to use an image strip in the sequencer for all the images that I already rendered didn't work&mdash;the render just copied the images into a new directory.  The Movie Clip node doesn't seem to accept an image strip as input, either, so that was not an option.  What I ended up doing was sequencing the animation to a movie file, then piping that into the Movie Clip node in the compositor. However, this required extra time, extra storage, and it rendered the default scene every frame before compositing, only to ignore the result.  Is there a way to use Blender's compositor either directly on an image sequence, or in conjunction with the video sequencer? How can I download an older version of Xcode? I am trying to download Xcode from the App Store, but it says that I have to have a newer version of macOS. But I don't have enough space on my computer to upgrade. Its like 8 gigs or something like that and if I only could download Xcode that was compatible with macOS Sierra that would be nice. Ubuntu 16.04 LTS Virtualbox 5.0.40 ubuntu r 115130  Today after upgrading to kernel 4.13.0-26 guest vbox machines started to crash whole ubuntu. just hard poweroff is working.  If I startup with kernel 4.10.0-42 everything works fine.  what may be the problem ? How do I test asynchronous Apex? This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, including more unit test resources, navigate to the  tag.  I'm testing asynchronous code - like Batch Apex, Queueable Apex, @future methods, or Scheduled Apex - and I'm getting unexpected results. It seems like portions of my code aren't running, or I'm getting confusing errors about batch invocations. How do I effectively test this kind of code? Why don't we include $\rho g h$ in a hydraulic jack below? Consider a hydraulic jack with massless pistons as follows.    The famous equation for this system is   $$ \frac{F_1}{A_1}=\frac{F_2}{A_2} $$  My question is why isn't the equation as follows?  $$ \frac{F_1}{A_1}=\frac{F_2}{A_2} + \rho g h $$  It is based on  my understanding that any points in the same horizontal line have the same pressure.  Could you spot my misconception? Interpretation of R's lm() output Ant-Man, shrinking, and weight Why would a partition be in use by the system if it isn't mounted? I've been migrating my system from btrfs to ext4 after running into performance issues with VMs. I have two hard drives in my laptop to work with. I've successfully moved my home partition, but the same steps I used aren't working for root.  Progress so far:  I've dd'd my root partition from /dev/sda3 into /dev/sdb3. I modified /etc/fstab to the following:  $ cat /etc/fstab #  # /etc/fstab: static file system information # # &lt;file system&gt; &lt;dir&gt;   &lt;type&gt;  &lt;options&gt;       &lt;dump&gt;  &lt;pass&gt; # UUID=95f13c34-96ca-49e3-bcb2-ff594df31506 /dev/sdb3               /               btrfs           rw,noatime,ssd,space_cache,discard      0 0  # UUID=0fe04f59-599f-41e2-ac30-2ad0f17a9727 /dev/sda2               /boot           ext2            rw,relatime     0 2  # UUID=44741e0f-924a-4841-80ef-2132bef84182 /dev/sda4               /home           ext4            rw,noatime,discard      0 0   and run sudo mkinitcpio -p linux. It seems to work. I'm able to boot by mounting the partition on the second disk. df shows:  $ df Filesystem      Size  Used Avail Use% Mounted on /dev/sdb3        28G   18G  9.8G  65% /   So, clearly, sdb3 is mounted, not sda3. Here's the problematic step: When I try to format sda3, which is supposedly unused, I get the following:  $ sudo mkfs.ext4 /dev/sda3 [sudo] password for stew:  mke2fs 1.42.11 (09-Jul-2014) /dev/sda3 contains a btrfs file system Proceed anyway? (y,n) y /dev/sda3 is apparently in use by the system; will not make a filesystem here!   sda3 is in use. How and why could it possibly be in use?  As per casey's comment, the output of mount:  mount | grep sd /dev/sdb3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime)   As per Warwick's comment, unmounting:  $ sudo umount /dev/sda3 umount: /dev/sda3: not mounted   Mounting and umounting sda3 elsewhere works successfully, but changes nothing.  Update: More fishy behavior:  $ mount | grep sd /dev/sdb3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime) $ sudo mount /dev/sda3 mnt [sudo] password for stew:  $ mount | grep sd /dev/sda3 on / type btrfs (rw,noatime,ssd,discard,space_cache) /dev/sda4 on /home type ext4 (rw,noatime,discard,data=ordered) /dev/sda2 on /boot type ext2 (rw,relatime) /dev/sda3 on /home/stew/mnt type btrfs (rw,relatime,ssd,discard,space_cache)   After mounting sda3, sdb3 is no longer mounter. Weird, huh?  As per mikeserv:  $ rmmod btrfs rmmod: ERROR: Module btrfs is in use   This is very much expected, since sdb3 is btrfs and supposed to be mounted to root. From my mkinitcpio.conf file:  MODULES="" HOOKS="base udev autodetect modconf block filesystems keyboard fsck" Why is "if not someobj:" better than "if someobj == None:" in Python? How to minimize the ink-to-data ratio for pgfplots ArcGIS Python Tool - Importing Custom Script Into ToolValidator Class How do I make the Messages that are sent to me stop going to my Mac? Built-in text editor in Terminal Is there a built-in text editor in the terminal on Lion?  (Like, for example, nano on Linux.) Recursive search in nautilus 3.6 completely breaks my keyboard navigation. I often navigate network volumes, and typing to get directly to a folder and clicking enter was very quick. Now typing removes everything in the view and imposes a 30 second delay which is completely useless.  If it showed whats in the current directory immediately, and then searched it would be fine, but as it is now I just want to turn it off. I couldn't find anything in dconf-settings. Anyone know how to disable it? I am looking for an adjective/noun for someone who is able to speak/ makes speeches very well and uses words effectively to influence/impress people. What is the shape of a black hole? I was thinking; what shape does a black hole have?. By 'Shape', I mean its form (e.g, circle , cylinder, sphere, torus, etc..).  We usually think of black holes as if they're plugholes (e.g, a flat circular object), but what if they're spherical? A spherical black hole would make much more sense. I would imagine than a black hole shaped like a basketball would be capable of pulling more mass towards it than a flat one, as it has a higher surface-to-volume ratio to do so.  Edit I know that it's probably a sphere, but when you think about it, a cylinder could also be a potential shape. Why do we use decibels instead of just using intensity to measure how loud things are? I have a raster height model and would like to calculate the horizontal geographic direction (north, east, etc. - orientation) of each cell, then calculate then the mean value of all these cells in one region (polygon). This is to get information about to what direction a vineyard is exposed to. How do I do this? I am traveling from Chennai to Atlanta. M first flight is to Frankfurt reaches at 8 30 AM. My second flight is scheduled at 10 45 AM.   Will the two hours transit time enough for boarding my second flight.  What should be my do's and dont's?  Update  Its more than enough. I was able to make it without any tension. What is C# analog of C++ std::pair? I'm interested: What is C#'s analog of std::pair in C++? I found System.Web.UI.Pair class, but I'd prefer something template-based.  Thank you!