24-70mm lens help

[tscanaan]

I purhased the Sigma 24-70mm lens because several people I know LOVE it and talked about how sharp it is. I am not having any luck with it. I have taken a few family sessions with it and no matter what I do the pics are never sharp!! I have tried different settings, so I am not sure if there is something wrong with the lens, if I am doing something wrong or if the lens just isn't as great as everyone made it out to be! Any advice?

[RobertTheFat]

What camera are you using? If it's one that has autofocus microadjustment, try recalibrating the lens with the camera.

[tscanaan]

I have the Canon 5D markiii

[TTMartin]

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@tscanaan wrote:

I purhased the Sigma 24-70mm lens because several people I know LOVE it and talked about how sharp it is. I am not having any luck with it. I have taken a few family sessions with it and no matter what I do the pics are never sharp!! I have tried different settings, so I am not sure if there is something wrong with the lens, if I am doing something wrong or if the lens just isn't as great as everyone made it out to be! Any advice?

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Sigma lenses are know for calibration issues. So much so that Sigma sells a lens dock so you can do the calibration on your own. You should first try Micro-Focus Adjusting your lens and see if it is within the adjustment range of the camera. I suggest using the DotTune method of Micro-Focus Adjustment.

[ebiggs1]

Now for the straight skinny of the current crop of 24-70mm lenses. I own all the currently available versions. Well, I did as I just sold my ef 24-70mm f2.8L USM verison 1. I bought the newer version 2 to replace it. And what a fantastic lens it is. It has no peers. It is that good.

BTW, the Sigma dock will not help you with the Sigma 24-70mm f2.8. It doesn't work with it.

The order of IQ is;

1st ef 24-70mm f2.8L USM II

2nd Tamron SP 24-70mm f/2.8 DI VC USD Lens

3rd ef 24-70mm f2.8L USM

     Tokina AT-X 24-70mm f/2.8 PRO FX    (tie for 3rd)

4th Sigma 24-70mm f/2.8 IF EX DG HSM

I bet your image is overall soft. If that is the case the micro focus adjustment will not help. If you could u/l a sample possibly we could tell for sure. What are you using to compare your Siggy to? It isn't going to be as sharp as a ef 50mm f1.8 for instance. However this is not to say the Sigma isn't a good lens because it is. It is a very good buy for its price point. It just isn't the sharpest tack in the box.

I also have the Nikon AF-S NIKKOR 24-70mm f/2.8E ED VR which is several hundred bucks more than the Canon but isn't as good or at least isn't any better.

[tscanaan]

This is one example.

It looks fine like this, but when I am in PS and zoom in to 50% or higher the faces are really grainy.

I have shot with a 35mm prior and can zoom in at 100% on those pics and they are still clear.

[ebiggs1]

Of course the example is a low res but to me it looks pretty typical for the Sigma 24-70mm f2.8.  Your settings are pretty conservative, and this is likely the norm but you might want to try and keep the ISO at 100 for this type shot.  The 5D Mk III is an outstanding camera for sharp photos.  Still you can not compare this zoom to a 35mm prime lens.

If you want to, Sigma will calibrate the lens to the camera.  You will need to send both in to Sigma.  The problem comes from the fact both lens and camera have manufacturing tolerances.  Both are totally within spec but you may have a lens that is on the positive side of the range and a camera that is on the negative side.  This difference in tolerance can become quite large in certain circumstances.

Bottom line, if you need 35mm prime IQ, you will have to drop the dime for a ef 24-70mm f2.8L USM II.

[RobertTheFat]

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@tscanaan wrote:

This is one example.

It looks fine like this, but when I am in PS and zoom in to 50% or higher the faces are really grainy.

I have shot with a 35mm prior and can zoom in at 100% on those pics and they are still clear.

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Where was the active autofocus point? The sharpest item in the picture may be the orange design on the sole of the man's shoe. If the camera was trying for the faces, you may have a front-focusing problem, and that could be addressed by autofocus microadjustment.

The overexposure of the principal subjects (illustrated by the washed-out faces and the glare at the top of the retriever's head) may also be making the picture appear less sharp. I might suspect overaggressive fill flash as the culprit.

[ebiggs1]

Bob from Boston,

There is no doubt the exposure is off by approx. 1/2 stop.  The shoe is not the focus point if you zoom in using PS to 200%, it becomes obvious.  The shot was at 26mm, even at f4, the DOF would take care of that anyway.  If the shoe was the foucs point, I doubt there would be enough adjustment to move it that far.

I decreased the exposure 1/2 stop and did lens correction.  It helps but even that will not help, or put something there that isn't there to begin with.  I believe this is as good as the Sigma lens can do.  Perhaps there is a fault with this lens as someone already offered, Sigma has had consistency problems in production.  The 24-70mm f2.8 is one of their newer lens designs. Sigma has made strides in QC since the olden days!  If the OP is in doubt, he needs to send it to SIgma and explain the issie.

Otherwise use it as is and do careful edits in post.  But don't do crazy crops!