Dust in lens! When is it "too much"?

[Morituri]

Hi guys! As always turning to the best forum out there when in need You guys are the best.

We all know that dust in lens isn't a big deal, if a deal at all since the dust in the lens is so out of focus that it basically becomes null and void and all that jazz. But when does it become an issue when the lens is TOO dirty?

I got two Nikon 50mm F1.8's, one focuses to 0.45m, the other to 0.6m. Now the 0.6 is all clean, but the 0.45m is murderous. Have a look at the picture I've linked to. Now that was taken with a mobile phone so you know that it's a bit more dust in there then you can see, I'd say 50% more. Now, I am no expert, you guys are, isn't that when you go "Ok now that is too much dust in there to start effecting image quality"

What do you guys think? Better use the other lens huh? The reason I am asking is I don't need two 50's obviously and going to sell one and need to know if THAT much dust will affect quality or not.

I haven't been able to take sample photos and compare since I don't have film nor chemicals at the moment and will take a while until I get some and need opinions until then.

Cheers guys.

 

[Rol_Lei Nut]

Probably won't make a visible difference in "easy" conditions, but will probably lower the contrast and make it much more flare prone in against-light & similar difficult conditions.

There is no set boundry for "too much" dust, just a progressive decrease of contrast & flare resistance performance until *you* notice it...
;-)

BTW: When I see "dust" that bad, I usually suspect fungus.

 

[Excalibur2]

When these questions are asked I always think of this link:-
http://www.lensrentals.com/news/2008.10.30/front-element-scratches