F stops for various shots

this is probably already somewhere in here - but I've done a brief search and not found what I'm looking for...

I'm trying to decide if our new Sigma 24-70 F2.8 EX DG (replacement version) is still not performing as it should. I believe I should be getting better quality images from it..

What would be a standard f stop for say a full length bride and groom shot that you would use? Bearing in mind it would be at say 50mm approx and standing a couple of meters away...

Some photos I took on the weekend were on F7.1 and still weren't overly sharp.. Light was bright.. I would have expected alot more from it.. i'm beginning to wonder if I'm doing something wrong ... :S

Maybe it's not you, but the lens?

Pixel peep and see if there's an issue with front or back focus, which is sometimes the issue with some lenses. With an f-stop at f/8 or close - with only one or two people in the frame, you should have good focus where you aimed your focus point.

If you feel unsure if you had everything within the focal plane, try this link and calculate the numbers: http://www.dofmaster.c​om/dofjs.html

What was your shutter speed?
Can you post an image so we can see what you mean?

We used to have a Sigma 24-70 f2.8 and it was generally a good, sharp lens - a bit soft at F2.8, and it would sometimes miss focus (on a 350D at the time), but we still got many good sharp photos out of it.

Rob

http://www.focustestch​art.com/

Do the test on a tripod, 3 times, refocus to infinity in better each time. Do it in a well let room, at F2.8, and at F8. Post the most representative images, preferably a 100% crop.

Thanks - we did all the test charts on the original lens and it was about 40mm front focusing! Hence why we got a replacement.. this one is about 5-10mm front which I would consider not too bad.. yet the photos are still not looking right :S I will post some tonight

Send it back, or have it calibrated.

Seems to be consistent with shooting at 24mm or at the other end.. apparently a trait of the lens.. we are going to try and take it back and exchange for something else.. may have to pay more but you get what you pay for .. perhaps Canon this time! :P

Get the 17-55, I likey.

that's what we're possibly considering..

5-10mm is far too much. On testing if it's not spot on, I'm not happy. Send it back to get it calibrated.

Yeah and that would take too long. Apparently it can't be done here in NZ the sigma agents have told me. They would need to send it to Japan. I dont have that long to wait. I have weddings to do. This is why they replaced our first one and after being told it would take a few days - that took 3 weeks too!! I'd rather take it back and get a refund and spend my money on something else that I can use straight away.

Well I have had niggly focus problems with my Tameron 28-75 2.8 and often wondered if it was a lens problem, well thanks to Tims link and 10 mins of my time I now know that its the operator not the lens at fault

Thanks for the link tim.

Martin.

i2iSTUDIOS wrote in post #2644303
5-10mm is far too much. On testing if it's not spot on, I'm not happy. Send it back to get it calibrated.