Combining two renders in PS or AE, to further reduce noise ?

[vkiuru]

Same camera angle, lighting, everything. Let's say the other one rendered for 4 hours, and the other for 3. Is there a way in Photoshop or After Effects, perhaps through layer blending modes to merge these two so when combined, noise could be negated even further?

I'd appreciate it if any of you could share some insight!

[racoonart]

multiply the 4 hour render by 4, multiply the 3 hour render by 3 , add one image to the other. After that divide everything by 7 ;)
You could of course do it with fractions too.

Edit: Keep in mind that this has to happen in linear space!

[maru]

Correct me if I'm wrong, but if the images were rendered with locked sampling "pattern", then won't blending them only make the noise worse?

[vkiuru]

Thanks, DeadClown.. it's that simple, eh? :P

But then again, what Maru said below. Though I just switched from dailies to A7.2 in order to try out rendering an animation through Rebus Farm. I might be wrong but wasn't the locked noise pattern introduced in the dailies? Anyway, off to try out that setup DeadClown mentioned. Thanks guys!

Correct me if I'm wrong, but if the images were rendered with locked sampling "pattern", then won't blending them only make the noise worse?