Aperture/Diaphragm Q...

[jtay025]

New to dslr, but I recently bought a Sigma 70-300mm apo lens and the diaphragm has 9 points, but it is asymmetrical to the point where it is noticeable when its stopped down, does this matter much? The reason why I'm asking is because the lens just isn't as tack sharp as I was imagining when stopped down a little bit at mid zoom - so can an irregular diaphragm be a cause for softness of image?

I've taken great pictures with this lens and am happy with it, just wondering if this particular unit is lacking some of the brilliance due to this observable flaw.

[cdifoto]

can an irregular diaphragm be a cause for softness of image?

I've taken great pictures with this lens and am happy with it, just wondering if this particular unit is lacking some of the brilliance due to this observable flaw.

It's "lacking brilliance" because it's a cheap lens. Period. Has nothing to do with the diaphragm. At least not directly. :)

If you want top image quality you have to pay for it or at least stick with primes if you want to spend under $400.