Question?!? Sigma 17-70mm vs Canon 50mm 1.8

Hi Everyone,

I just got my Sigma 17-70mm (no OS version) and the pictures seem to be fine (sharp, colour saturation, contrast) but I noticed the viewfinder looks different. When I zoom further in towards 70mm I can see what looks like a speckled (noise) pattern (grainy) in the viewfinder, really really uniform in the whole thing and easier to see against a solid surface??

What is it? Does it mean its broken because my 50mm prime doesn't have the thing happen (problem??). Any help is appreciated as its hard to google for something so specific like this or I had trouble anyway.

Thank you so much!

i think it comes down to the Sigma being a slower lens and it explains why I see it less when it is open up at 2.8 compared to 4.5 at 70mm? is that right?

Since the 17-70mm is "only" f4.5 at the long end, it is not getting as much light to the viewfinder as an f1.8 or f1.4 lens will. IN fact it is like 8 times less light. You are just noticing it getting darker. Nothing to worry about.

tkbslc wrote in post #9911513
Since the 17-70mm is "only" f4.5 at the long end, it is not getting as much light to the viewfinder as an f1.8 or f1.4 lens will. IN fact it is like 8 times less light. You are just noticing it getting darker. Nothing to worry about.

Yeah. I guess I sort of panicked as I've only really used the 50mm 1.8 and that is clear as day so moving to the 17-70 I noticed it a bit at 2.8 and then 4.5 @ 70 and I thought my 2nd hand Sigma 17-70 was a dud.... =D but it seems all is good, faster lens less grain, slow lens more grain (viewfinder)... and I 'discovered' my DOF button again.. always forget about it.

I saw this just to help someone else maybe..

http://www.flickr.com …iscuss/72157621​477847786/

thanks! I can't wait to take some real shots tomorrow and not just panicked 'test' shots to see if the grain was visible in the finished shot. it wasn't.