How sharp should my Sigma 17-70 be

[ben4633]

I have taken alot of pics with my 17-70 and for the most part I love it, however should it be sharper than this. Let me know what you think and maybe post some pics you have. This pic was taken at F4.5 1/1000 iso 400. Is is possible that the reason it is a bit soft is because I took this at f4.5?

[ed rader]

if the first image hasn't been cropped and you used center point focus it looks to me that you did not focus on the cat's left eye, which is where i would have focussed.

ed rader

[_aravena]

He's killing th camera man! What's up with that!?!

But i'll have to go with rader on that. What point focus were you using? Maybe you cropped where you wanted to focus but not where you focused, ya know?

[jptsr1]

I have taken alot of pics with my 17-70 and for the most part I love it, however should it be sharper than this. Let me know what you think and maybe post some pics you have. This pic was taken at F4.5 1/1000 iso 400. Is is possible that the reason it is a bit soft is because I took this at f4.5?

I've gone through the exact same thing with my 17-70. just when i think its the sharpest tack in the box i have an outing where my stuff is way soft. its always operator error with me. once i sit down and review the shots from a bad day ill realise my focus point is off or my shutter speed is low or i didn't pay attention to my aperture.

if you need to reassure yourself about the capabilities of the lens take as many the potential operator error opportunities out of the equation. set your rig on a tripod and focus dead on a still subject in good light at like f8 or so. chances are its not the lens.

nice cat.

J.

[ben4633]

Ok, here is a 100% crop on the cats left eye. Do you think its just not totally focusing right? And almost every picture I take I use center point auto focus, is this the wrong technique?

[TMR Design]

HI Ben,

The Sigma 17-70mm lens is a fine lens that can produce tack sharp images. If you follow the lens threads you will find that there are some QC issues with Sigma but always easily resolved if you happen to have a bad copy. As others are suggesting, the AF point will make a huge difference especially with larger apertures.

Regarding example images that are sharp. Browse the 17-70mm archive thread (http://photography-on-the.net/forum/showthread.php?t=186589) and I'm sure you'll see images that are very sharp.

[TMR Design]

Ok, here is a 100% crop on the cats left eye. Do you think its just not totally focusing right? And almost every picture I take I use center point auto focus, is this the wrong technique?

Are you using center AF point to focus and then recompose? or are you just composing and the center AF is selected.

[ed rader]

Ok, here is a 100% crop on the cats left eye. Do you think its just not totally focusing right? And almost every picture I take I use center point auto focus, is this the wrong technique?


that's the cat's right eye :D ! where did you focus? it looks to me that you may have focussed behind the cat or on its leg (if you used center point and the first pic is not a crop).

ed rader

[jptsr1]

Ok, here is a 100% crop on the cats left eye. Do you think its just not totally focusing right? And almost every picture I take I use center point auto focus, is this the wrong technique?

but is that where you focused when you took the picture? to me it looks like the focus point may have been a little further left. the grass in front of the cats belly looks pretty sharp.

J.

[jptsr1]

oops, Ed beat me to it.

J.

[olly_k]

HI Ben,

The Sigma 17-70mm lens is a fine lens that can produce tack sharp images. If you follow the lens threads you will find that there are some QC issues with Sigma but always easily resolved if you happen to have a bad copy. As others are suggesting, the AF point will make a huge difference especially with larger apertures.

Regarding example images that are sharp. Browse the 17-70mm archive thread (http://photography-on-the.net/forum/showthread.php?t=186589) and I'm sure you'll see images that are very sharp.

Trouble is TMR, I think many images from these archive shots are very missleading where lens sharpness is concerned. Yes they show lovely images can be produced, but I bet images that are reduced in size and processed actually could be produced on almost any lens!

I would like to see a standard test, such as tripod, a 100W bulb / mid day sun or whatever with ALL exif data and a load of batteries or some other common target. Surely we would all get a much better idea of how sharp our lens's really are, and then be able to comment accordingly.

[TMR Design]

Hi olly,

This is true. I agree with you about images in the archive threads but they can give insight and lots of commentary about using the lens and its performance. Even without images, when many people are reporting things like "I love how sharp this lens is", it's a good reflection on its performance.

[ben4633]

Ok, so I took some test shots. Both shots were taken at f/8, the first at 70mm and the second at 35mm. To me they both looked pretty sharp, but I just wanted your opinion on these shots. I guess this would also prove that the first pic I posted of the cat is a bit out of focus. Let me know what you think

[ben4633]

Actually this is a better shot of the f/8 @70mm. After I looked at the post it was the wrong shot, here is the right one. by the way I used center point autofocus and the focus point was dead center of the zero. let me know what you think thanks again.

[TMR Design]

That's pretty sharp Ben. I don't see any problem and I'm glad you posted the new image. I was a bit concerned when I saw the first one.

I think you have a sharp copy.

[ben4633]

Thanks that makes me feel better, at least now I know that its operator error.

[pepperoni]

One more quick comment on the original picture. That photo was taken at 70mm at f4.5. That's wide open for that focal range, and most all lenses are not their sharpest wide open. I think you have a good lens.

$.02
:cool: