Sigma 24-70 too soft?

Hi eveyone!

I hope you can give me some thoughts on this. I have a new Sigma 24-70 2.8 DG Macro. At the suggestions from this board, after I got it and used it for a while, I conducted a focus test, and found some front focusing. I sent it back to Sigma for recalibration, and just received it back from them yesterday. Of course the first thing I did was another focus test. Some of the results are posted below - and my main question is whether I am being too picky with this lens, or if I should send it back again.

All test shots were with a Canon 20D, ISO 100, aperture priority (F2.8), tripod mounted at a 45 degree angle to the focus chart, mirror lockup enabled and cable release was used. Images are shot in RAW, w/o any post processing other than adding descriptions. Here are the results:

Reference shot with a Canon 50mm 1.8 @ F2.8

I think is not soft. It look´s to me like is still front focusing a little bit when is going to the 50-70 mm focal distance range.

I shall suggest you to shoot some real things to check it.

Also it looks like in the nearest distance trends to front focusing, so be careful about the minimum focus distance !! (Macro mode....) Be sure that the green led for focus confirmation is on and not flashing !!.

In my experience, the 45 º angle test focus chart are tricky. Personally I prefer to use this one because is more reliable (a big target is perpendicular to the axis & parallel to the camera, noway to miss it):

http://www.canon-dslr.com …/Canon_SLR_Focu​s_Test.htm

Juan Zas wrote in post #2234036
In my experience, the 45 º angle test focus chart are tricky. Personally I prefer to use this one because is more reliable (a big target is perpendicular to the axis & parallel to the camera, noway to miss it):

http://www.canon-dslr.com …/Canon_SLR_Focu​s_Test.htm

Also you should press you shutter half way three times. And pre-focus further and closer to verify it focuses correctly coming from a longer and shorter focus distance to the target.

davidfig wrote in post #2234405
Also you should press you shutter half way three times. And pre-focus further and closer to verify it focuses correctly coming from a longer and shorter focus distance to the target.

Yes. I usually take three ot four shoots for each set up, looking for consistence (as far as I remember it is explained in the docs):

1 - With the distance dial set at Infinitum, half press, shoot

2- With the distance dial set at closest distance, , half press, shoot

3- Something set in the middle, , half press, shoot

4 - Repeat last one.

I just have to jump in and ask, are you more than the min focus distance of:

Minimum focusing distance of 40cm (15.7 inches)

More than a fair question - yes I was about 24 inches from the subject.

Scott, if you focused on "this text should be...", then the problem seems to be front focusing. Also, the pics look underexposed or/and under poor lighting. Correcting this will give better focusing and yes, open wide some copies of that lens seem to be just a little soft.

I suggest you again try to make also real shoots and see how they look and the IQ you get. My copy is pretty good even wide open in the distance if it´s wright exposured (even in low light conditions). Someones, as far as remember from other threads trends to front focusing a little bit when they are in the nearest field (correct light is also important). Just use it and see how it´s performing. If you are happy, then don´t worry and be happy. Sometime the tests are not so reliable as the real practice.

The text at the bottom of each photo is spot on. I am not a fan of lens tests as there are just too many variables that must be controlled and most do not, or cannot, control them. Shoot some real world items and see it you like it. Unless your goal is to be a test pattern photographer, leave the test patterns alone.

I have the same lens and I feel my copy is a bit soft too. Used it at my friend's wedding and the pictures are just a bit on the soft side compare to my 70-200 4L.

Grooby wrote in post #2236607
I have the same lens and I feel my copy is a bit soft too. Used it at my friend's wedding and the pictures are just a bit on the soft side compare to my 70-200 4L.

Apples & Oranges