Grumpy_Mike:
Well you could try a filter with a resistor and capacitor but it would be good to use a proper sensor and a realistic value of feed back resistor.
I know a decent sensor would be better, but a PAR sensor is in the price range of 180$. I thought the geniuses here would come up with a nice diagram that I could actually use...
Knowing that the feedback resistor is way to much, but since you guys love gobbling up those diagrams, and this was one I could find in a whim...I posted this one, not expecting the funny replies...Please give Erdin a dollar cause he's SOOO funny 
Any other ideas how I could measure PAR without the op-amp?
Erni:
I just found this.5 minutes reading
http://dkc1.digikey.com/us/en/tod/ADI/Top5Problems_NoAudio/Top5Problems_NoAudio.html
Thank you for the useful link. Saw it earlier this weekend, but didn't know what to make of all those diagrams and explanations... Still don't actually, that's why I came here to learn something...So just for the heck of it I'm going to try my best to decipher the 5min course (it already took me a whole lot longer 
) and come back with what i've learned. And then please comment on this, even if it's just to make fun! Because that just means one has read my jibberjabber and understands it better then I do
Thank you all for reading and like I said earlier on this forum... I'm not going to give up that easy!