With the code I gave as example ? I really doubt it...
It mean that either you have an over powerful computer or a "slow brain" (note that it's not an insult, there's really people with a brain that take more time to process visual information and can miss a small part of the said information).
The flash happen because, for a fraction of time, between the
hide statement and the following
show statement, Ren'py fallback to the actual background (the image comming from the last
scene statement you used). So, if you have something like this :
Code:
scene imageA
"some dialog"
show imageB
hide imageB
show imageC
Ren'py will do :
- Display imageA ;
- Display the dialog line ;
- Display imageB on top of imageA ;
- Display imageA (since imageB is no more on top of it) ;
- Display imageC on top of imageA.
Now, the longer is this said "fraction of time", the more likely the flash will be visible.
This will with :
Code:
scene imageA
"some dialog"
scene imageB
scene imageC
Ren'py will do :
- Display imageA ;
- Display the dialog line ;
- Replace imageA with imageB ;
- Replace imageB with imageC ;
Yes, because it's what
scene is intended to, while actually you misuse the
show and
hide statement. Like implied above, when using them, you display the image on top of the image defined with the
scene statement ; so, Ren'py effectively display two images at the same time, but like they have the same size, you only see one.
yup..i made my mom a lesbian and thats her lover 
