I've seen on several sites that sell airbrushes that needles come in a variety of diameters. What do the various sizes let you do? And, can you adjust the needle in relation to the nozzle, affecting the air/paint mixture? If so, how do you do that? And why would you?

Smaller diameter tips allow for finer detail. Although it can be more difficult to spray certain paints with a small tip. .5 seems to be somewhat of a standard that works really well for plug building applications. I have a .5mm iwata and it works great. It takes some practice with thinning paints to the right consistency to get the finish you are looking for.

Different Diameters allow for finer detail.

as far as air/paint mix...I don't know if thats exactly what its doing.....more of the amount of paint leaving the nozzle......don't know if its actually adjusting the ratio

I would think the regulator on the tank is what actually adjusts the Air/Paint ratio

the only way to adjust the air/paint ratio is to pull back the trigger more. or raise lower the air pressure.
Bigger needles and tips = more paint flow = less detail= more coverage

when airbrushes were first made they were ment for lacquer/inks paints,pigment's were ground very fine and lacquer being the carryer and thinner then water,,that's why their were so good for detail with the small dia needles. now along comes water based paints, heavy pigments and the carryer thats like milk, so larger dia needles were needed to shoot these new paints through the gun...when thinning down these new water based paints, you loose some of the true color because the pigments are spread out further apart....think in turms of pixels in a screen, so many dots per square inch..the finner the grain the better the picture.....it's got nothing to do with air..it's all about how fine/big the pigments are and whats used to carry the pigments....heavy= large dia neede...fine= smaller dia neelde.

So what I'm getting .3mm tip is a fine tip and .5mm is standard and larger. I don't know what tip is in my Central Pneumatic 2 stage. Available tips are .3mm, .4mm and .5mm. I 'd like to try a finer tip. Is the lower # tip the finer one?

.3 needle would be the smallest for your gun,but make sure you also get the tip[nose] that will fit that size needle. one size tip doesn't fit all needle sizes.

you still up:hihi:

nope...wife took care of that problem:hee:

Does the larger tip work better with pearl paints?

all my guns have .3 needles..they shoot all paints just fine,,but I also thin all my paints reguardless of color.