I'm sure these kinds of questions are asked all the time but is it possible to mount an old SLR lens like this on a newer DLSR camera? The Tokina lens is made for a Pentax K1000 and I have a Nikon D3300. I've also got a Canon FD 70-210mm zoom lens but I read online you can't use those with DSLR bodies. Does anybody know where I could find an adapter for these lenses, if they're even compatible? Any info would be appreciated.
I've got some lenses of brand X, but I've just got a new camera of brand Y. How can I tell if it's possible to use my lenses on my camera? I accept that I may lose a lot of automatic functionality like autofocus, aperture control and metering when using an adapter to connect the two.
In my question  I asked about the definition and usage of the word "model", for which I was told the following definition:     A formula of propositional logic is true under an interpretation iff   the interpretation assigns the truth value T to that formula. If a   formula is true under an interpretation, then that interpretation is   called a model of that formula.   An interpetation satisfies a formula φ iff it is a model of the formula. Same for a set $\Gamma$ of formulas, if an interpretation satisfies all the formulas in $\Gamma$ then it is a model of $\Gamma$. Then if we say $\Gamma \vDash \varphi$ then $\varphi$ is a semantic consequence of $\Gamma$ / is satisfied in all "models" of $\Gamma$ (true whenever everything in $\Gamma$ is true).  This also matches the definitions for model as seen on the Wiki for  and .  All good so far. But when I get really confused when I see posts like  where they use "models" as a word meaning "satisfies all the axioms in a theory."  From Asaf's answer:     Models are structures, and structures are models. But when we say   "model" we mean that there is a particular theory which holds in the   structure, and when we say "structure" we are mainly interested in an   arbitrary interpretation of the language.   From Metin's answer:     A structure is a set with some interpretable symbols(constants,   relations and functions) within a fixed language. You do not ask for   more from a structure.      However...      A model (of a theory) is a structure which satisfies the axioms of the   theory. It makes more "structural sense"...   And then from one of Asaf's comments:     When I say "a model of 𝖹𝖥𝖢" they also know, immediately, that I am   talking about a model which satisfies all the axioms of 𝖹𝖥𝖢.   So I am unclear on which definition is correct or if this is the same word being used in two different ways or if this is "logical model" versus "semantic model" or something else entirely.  On the one hand we seem to have "model" meaning "any interpretation that satisfies a formula or set of formulas." On the other hand we have "model" meaning "Interpretation that satisfies all the axioms of a theory".  From the Wiki article on  we see also:     For a given theory in model theory, a structure is called a model, if   it satisfies the defining axioms of that theory.   So which is it exactly? Does "model" have a different meaning in propositional logic compared to model theory or first-order logic or set theory etc? Equation left margin I have equations inside an environment which has a larger left-margin than the main text (analogous to an enumerate/itemize environment, implemented with the changepage package's adjustwidth environment). Just as equations in enumerate/itemize behave, the equations are centered with respect to the entire text, rather than just the width of the container environment. I want the latter behavior.  I'm trying to accomplish this by wrapping all display-math in minipages. Namely, I'm modifying the mathdisplay environment in amsmath.sty as follows:  \makeatletter \let\oldmd\mathdisplay \def\mathdisplay#1{%   \newline   \begin{minipage}{\textwidth-\@totalleftmargin}%     \oldmd{#1}% } \let\oldendmd\endmathdisplay \def\endmathdisplay#1{%   \oldendmd{#1}%   \end{minipage} } \makeatother   This is almost working, but there are some issues with spacing which I don't understand how to fix. Here's how the the normal \[ ... \] and numbered \begin{equation} ... \end{equation} look with the above modification:      My main confusion is why the numbered version is behaving so differently from the unnumbered. But all in all I want to fix this so that the spacing above and below is even as it usually is. Any help is appreciated, thanks.  Edit: Here's a compilable example:  \documentclass{amsart}  \usepackage{lipsum} \usepackage{calc} \usepackage{changepage}  \makeatletter \let\oldmd\mathdisplay \def\mathdisplay#1{%   \newline   \begin{minipage}{\textwidth-\@totalleftmargin}%     \oldmd{#1}% } \let\oldendmd\endmathdisplay \def\endmathdisplay#1{%   \oldendmd{#1}%   \end{minipage} } \makeatother  \setlength{\parindent}{0pt}  \begin{document}  \lipsum[1]  \begin{adjustwidth}{20pt}{} \lipsum[2] \[ x \mapsto \hom(-,x) \]  \lipsum[3] \begin{equation}   y \mapsto \hom(y,-) \end{equation} \lipsum[4] \end{adjustwidth}  \lipsum[5]  \end{document} "As part of" versus "as a part of" Berlin Public Transport Ticket Validity I have purchased an AB zone Berlin 7 day transport ticket and validated it on Sunday 17th April so hopefully it will be valid until Sunday 24th.  I validated the ticket at about 10:00am so I guess 1000 is the time I validated? But what are the numbers 15 and 6 and letters 'So' correspond to? How (if checked by a guard) can they tell if the ticket is valid? And how can I as a customer tell when it is validated to? How do I perform a Perl substitution on a string while keeping the original? In Perl, what is a good way to perform a replacement on a string using a regular expression and store the value in a different variable, without changing the original?  I usually just copy the string to a new variable then bind it to the s/// regex that does the replacement on the new string, but I was wondering if there is a better way to do this?  $newstring = $oldstring; $newstring =~ s/foo/bar/g; What's that ship in the opening credits of 'Star Trek: Enterprise'? Checking for a file and whether it is readable and writable I'm trying to write a script that will look for a certain .txt file saved to my desktop.  I want the script to be able to check if this file exists and then check to see if it is readable and writable.  Any hints? Proof that an integral domain that is a finite-dimensional $F$-vector space is in fact a field What are the most commonly used and basic Apache htaccess redirects? How to install an application that requires gksu package on ubuntu 18.04? I downloaded the Upwork desktop App on ubuntu 18.04. When I open it with Gdebi package installer I saw this error:    I tried to install gksu manually via sudo apt install gksu but I got this error  Building dependency tree        Reading state information... Done Package gksu is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'gksu' has no installation candidate   How can I install this software on ubuntu 18.04 (I download it yesturday so it is the most recent version on upwork website) ? Permission for snap applications I have some trouble with the Ubuntu notepadqq package. After opening a file from my apache webroot I cannot see any content. Saving the file is also not possible. I thougt this would be a classic permission issue. Therefore, I changed the group of the webroot from root to www-data and added my user to this group. Permissions are 775, so in theory it should now be possible for me to edit files in my webroot. But nevertheless, when I open a file of this directory with notepadqq, it still only shows an empty file.  When using gksudo notepadqq I get the following error message:  No protocol specified QXcbConnection: Could not connect to display :0   I figured out that notepadqq is a so called snap application and I wonder if this is the reason for my problems.  Can someone give me a hint how I could fix this issue (without using 777 permissions)? Cost increase and suspend Where is composition tab in QGIS Composer to change page size? I am trying to change the page size in the QGIS 3.0 Composer but I am not able to see the Composition tab.  I have right clicked an empty space in the toolbar but did not see anything about composition.  I am using Windows 7.  I tried looking at the QGIS docs but they are still in testing. I want to encrypt a USB stick, and be able to decrypt it on Windows as well as Ubuntu. How do I do this &amp; what programs do I need to use? Zero visibility while editing a message in a chat room "Unfortunately, ... has stopped" when Downloading file in Android Does assigning objects to null in Java impact garbage collection? Does assigning an unused object reference to null in Java improve the garbage collection process in any measurable way?  My experience with Java (and C#) has taught me that is often counter intuitive to try and outsmart the virtual machine or JIT compiler, but I've seen co-workers use this method and I am curious if this is a good practice to pick up or one of those voodoo programming superstitions? How to determine whether a unique factorization domain is a principal ideal domain? Could someone please provide an example of a unique factorization domain that is not a principal ideal domain?  Furthermore, is there some way to determine whether a UFD is a PID? How do I center a container in my HTML/CSS? "Battery Health" in macOS Catalina 10.15.5? I have just installed the macOS Catalina 10.15.5 update on my 11" Mid 2013 MacBook Air. The update is working fine.  The MacBook Air specifications on the Wikipedia page says that this model has a lithium-ion battery, 'tho I haven't unscrewed the case to look. But the new Battery Health controls in System Preferences → Energy Saver don't appear.  Not a lithium-ion battery? Or perhaps other differences in this model prevent Battery Health from showing up? Something else?