But then you're overexposing neg film by 1/3 stop, which you will never notice, and underexposing slide film by 2/3s stop, which you WILL notice.
Originally Posted by keithwms
For neg film I too pretty much just treat it as f/4. If I'm shooting slide film hand held, I'm doing it in 35mm and have TTL metering anyway. If I'm shooting slide film in medium format I am probably working off a tripod or in decent light and won't be shooting my one medium format 3.5 lens (on my Yashicamat) wide open anyway. And in 4x5 I don't have any lenses that fast anyway. So for practical purposes it's a non-issue.
Even slide film can generally handle 1/3 stop overexposure though it will change the look, but if you treat it as half way between 2.8 and 4 you will be only 1/6th stop off and even in slide film you won't notice that.