Question on the Sigma 24 - 70 lens

thebaz

When my 24 -70 lens is wide open at 2.8 , I have found images a bit soft, am I better not going wide open, and using the apperature at next level up , 3.2 ?

Thanks lot,
b

Ricky91t

Possibly higher than 3.2,Work through the range and find the sharp/sweet spot of the lens,Figure out the best aperture for DOF and sharpness and stick to that,My sigma 20-40 f/2.8 used to be soft bumping it up to f/4 would sort on but since getting a 1.3x crop the issue is gone

sineadw

On my Canon-fit one the sweet spot seems to be about f8. In fairness to the lens though, any lens will struggle to varying degrees at maximum aperture. You're pushing it to the very limits of its design.

pieye

Generally, even with the best lenses, if you want sharp you keep at least two stops away from the top and the bottom of the range... no lens works best wide open:rolleyes:, except maybe a pinhole.

thebaz

Thanks all - begining to regret not saving up for a Nikon brand one, which i'd expect would be less soft - My old 50 1.8 used to be grand wide open , but have noticed the 1.4 goes soft when it is wide open -

Ill try using it at 3.2 , but in dark venues , I keep maxing it out

Reoil

Why buy a 2.8 if you can't use it at that?
I bought the Nikon 24-70mm last month, no complaints at all.
Same in any market - you get what you pay for...

thebaz

Reoil wrote: »

Why buy a 2.8 if you can't use it at that?
...

Money , or lack of in my case .... anyway maybe it is trial and error , once again tonight i pushed it to max, and was happy eneough with results from these trials - first 3 images on

http://www.flickr.com/photos/thebaz/

pete4130

I had the Sigma 24-70 and sold it. Not what I wanted it to do for the money I paid for it. The Nikon equivelant (after 5 months waiting for it to be fixed!!! grrrr!!!!) is erfect at 2.8

you do get what you pay for. The Nikon 50mm 1.4 is very soft towards the edges at 1.4 and only almost sharp near the centre (moreso on the D3 than the D300!!) but its the price you pay for veery sharp glass. I love my 50mm 1.4 and wouldn trade it for a Nikon 24-70mm 2.8 if I had to.

2.2 is ok on the 50mm 1.4. The Sigma 24-70 was a non ruinner for me after 2-3 months. It just didn't do it for me.

The 50mm 1.4 has to be kept centrd really. Save for the Nikon 24-70 2.8. It is worth it!

AnCatDubh

I understand that particularly in zoom lens construction you will find that the lens won't perform consistently over the entire focal range and aperture range. The sweet spot of a lens varies with every lens but best performance of that lens can generally be found somewhere in the middle of the focal length and middle of the aperture. Moving away from whatever that is and your resultant image will degrade slightly. This mightn't be noticeable / may be perfectly acceptable to a normal viewing eye and will depend on the build and quality of the lens. I know with cheaper lens (happens to be sigma in this case) it is very noticeable particularly at both extremes of the focal lengths so I try to avoid them.

The other thing to satisfy yourself with and not to forget in all of this is that at f2.8 -depending on other DOF parameters, you may be dealing with very shallow depth of field which could be a source of 'softness' also. This still pains me when I shoot the 50mm f1.7 wide open and manual focus which I think is more my lack of ability than a fault of the lens Run your setup through the DOF master to see what depth of field you were dealing with.

thebaz

I would assume then that the 2.8 works ok at 24 mm, but as you zoom in , you would need to adjust Apperature accordingly, to retain sharpness ?

So at 70 mm, might only be sharp at F 5.6 or something

sasar

Great link to compare canon vs sigma