Ah, of course, I didn’t think to look at \scriptfont3. It’s been a long time since I’ve looked this deep into TeX internals.

-dh

>
> Am Thu, 1 Oct 2020 22:47:31 -0500 schrieb Don Hosek:
>
>> While looking into this question https://tex.stackexchange.com/questions/565031/slightly-bigger-integral-in-exponent <https://tex.stackexchange.com/questions/565031/slightly-bigger-integral-in-exponent> I found that the formatting of \int differs slightly when using the amsmath package vs the base LaTeX with the former using a scriptstyle integral while the base uses a textstyle integral.
>
>> So the questions are: (1) what’s happening differently in amsmath
>> to change the appearance of the integral
>
> amsmath use a different cmex font:
>
> cmextra/cmex7.pfb instead of cmex10.pfb because of this code part
>
>
>
> \ifnum\cmex@opt=7 \relax
>  \DeclareFontShape{OMX}{cmex}{m}{n}{%
>    <-8>cmex7<8>cmex8<9>cmex9%
>    <10><10.95><12><14.4><17.28><20.74><24.88>cmex10%
>  }{}%
>  \expandafter\let\csname OMX/cmex/m/n/10\endcsname\relax
> \else
>
> you can get the "classical" appearance with
>
> \usepackage[cmex10]{amsmath}
>
>
>> and (b) which is the correct behavior?
>
> Well like always, it is a matter of taste, but I would say they made
> the change because they think it looks better like this and I agree.
>
>
> --
> Ulrike Fischer
> http://www.troubleshooting-tex.de/