If the film has been thoroughly stopped (in an acid stop) and the light level is not blindingly brilliant, the chances of negatives being ruined by "printing out" when exposed to light in the short time it takes to get to light insensitivity in the fixer is negligible, providing your fixer doesn't reactivate carried-over developer (i.e., you need an acid or at least neutral fix), peeking won't hurt anything; it's just inconvenient for roll film, and even for sheet film developed in trays unless you have a foot or elbow switch for the light.
It's fun to see the cloudy image clear (and informative for beginners), but once the novelty has worn off, totally unnecessary. If you're really worried about your fixer activity, you should do a clip test beforehand.
But, if you enjoy watching the film clearing in the fixer tray, and you've not experienced problems with printing out, then what the heck? Have fun.
Be aware, though, that carried-over developer can be reactivated by an alkaline fixer (e.g., TF-4, etc.). If you're using one of these, I'd leave the lights off.
Doremus
It's fun to see the cloudy image clear (and informative for beginners), but once the novelty has worn off, totally unnecessary. If you're really worried about your fixer activity, you should do a clip test beforehand.
But, if you enjoy watching the film clearing in the fixer tray, and you've not experienced problems with printing out, then what the heck? Have fun.
Be aware, though, that carried-over developer can be reactivated by an alkaline fixer (e.g., TF-4, etc.). If you're using one of these, I'd leave the lights off.
Doremus
Last edited: