why does using nodes with to in TikZ result in grossly missized labels?

Question

As much as I love TikZ, its trouble producing consistent output on different computers is getting to me. At the moment, I'm having trouble because when I use the to command, and nodes inside the draw command, the fonts sizes are all wrong, and the nodes often misplaces labels. This seems to be a quirk of my current computer, and some code I wrote on another computer now doesn't compile right (incidentally, I just checked; this compiles fine on my old laptop). For example, the code

\[
\epsilon=\tikz[baseline,very thick,scale=2.5]{ 
\draw[<-] (.2,.1) to[out=-120,in=-60] (-.2,.1)  
node[at end,above left,scale=.8]{$i$}
node[at start,above right,scale=.8]{$i$};
\node[scale=.8] at (0,.3){$\lambda$}; 
\node[scale=.8] at (0,-.2){$\lambda+\alpha_i$};}\qquad \qquad
\epsilon'=\tikz[baseline,very thick,scale=2.5]{
\draw[->] (.2,.1)to[out=-120,in=-60] (-.2,.1) 
node[at end,above left,scale=.8]{$i$} 
node[at start,above right,scale=.8]{$i$};
\node[scale=.8] at(0,.3){$\lambda$}; 
\node[scale=.8] at (0,-.2){$\lambda-\alpha_i$};}
\]

produces

What's with the crazy big i's? Is there something I can do to fix this?

As reference, if I make the nodes free-standing and change the code to

\[
\epsilon=\tikz[baseline,very thick,scale=2.5]{\draw[<-] (.2,.1)
  to[out=-120,in=-60] (-.2,.1);  \node at (.2,.2) [scale=.8]{$i$};
  \node at (-.2,.2)[scale=.8]{$i$};\node[scale=.8] at
  (0,.3){$\lambda$}; \node[scale=.8] at (0,-.2){$\lambda+\alpha_i$};}\qquad \qquad
\epsilon'=\tikz[baseline,very thick,scale=2.5]{\draw[->] (.2,.1)
  to[out=-120,in=-60] (-.2,.1); \node at (.2,.2) [scale=.8]{$i$};
  \node at (-.2,.2)[scale=.8]{$i$};\node[scale=.8] at
  (0,.3){$\lambda$}; \node[scale=.8] at (0,-.2){$\lambda-\alpha_i$};}
\]

I get basically what I intended.

Answer 1

I think that the good syntax is \draw (a) to node {} (b); like in the example of the pgfmanual :

\begin{tikzpicture}
  \draw (0,0) .. controls (6,1) and (9,1) ..
    node[near start,sloped,above] {near start}
    node {midway}
    node[very near end,sloped,below] {very near end} (12,0);
\end{tikzpicture}

In your case :

\documentclass{article}
\usepackage{tikz}

\begin{document} 

 $\epsilon$=
\tikz [baseline,
       very thick,
       scale=2.5]{%                   
\draw[<-] (.2,.1) to [out=-120,in=-60]  
      node [at end,above left]     {$i$}
      node [at start,above right]  {$i$}
      (-.2,.1)   ;
\node at (0,.3){$\lambda$}; 
\node at (0,-.2){$\lambda+\alpha_i$};  
} 
\end{document} 

Remark : I don't understand scale=.8 inside the options of node ! perhaps you want to reduce the size of the text ? but it's this case, I think you reduce the size of the node too. I think it's preferable to avoid this and to use something like font=\scriptsize.