Can you tell the difference?

[scootermcq]

I have shot these two pictures with a D90

One is an 18-70 & one is a 50mm prime

Flashes were set manually, so they would not change exposure
Both lenses were obviously at 50mm
Both F4.8 1/60

Which image seems sharper to you?

Left or Right?

[OsmosisStudios]

I'd say the one on the left is sharper, looking at the hair, BUT.
I'd say the one on the right is sharper in sections of the clothing.

I'm betting the one on the left is the prime.

That being said, the 18-70 is no slouch (I know, I have one) and f/4.8 isnt exactly the primes strongest point. Also, under ideal lighting conditions (like a studio), the differences between one and another are so minute that it barely matters.

I shoot the 18-70 zoom in a studio setting because of the focal length versatility.

[scootermcq]

Well, maybe that is why I am having such a hard time seeing the difference....

They were both shot under softboxes from left and right feathered across the subject, so lighting was pretty optimal.

The right image is the prime.

[jdepould]

Go shoot in crap light and you'll see the difference right quick.

[BCampbell]

They're such low resolution that it hardly matters what lens you use.

You could be using a 20 year old kit lens from a film SLR, if you scale them down that much.

If you post 50% or 100% scale examples the differences will probably show up more obviously, but as other have also said under strong light conditions the difference between good and mediocre glass start to fade.

Anyway, color & contrast on the one on the right seems a little better to me, but again, at this size who knows.