Sigma 10-20 sharpness

Hodders · 19 Sep 2008 at 14:51

I've just been out and taken a couple of shots at about 1.5m away from a brick wall at f4 and f8. Below are two 100% centre frame crops straight from the camera. Both shots were on 10mm. EXIF info should be there.

Do I have a sharp copy or not (seems OK to me) ?

1) f4

2) f4 - edge of frame

3) f8

4) f8 edge of frame

5) f16 - center

6) f16 - edge of frame

A lot better at f16 !

Paul11 · 19 Sep 2008 at 15:00

i dont know if im right or not, but as far as i understand, you shouldnt crop as its the edges of the image that you are looking at to see if they are sharp or not

I am going to go and test my lens now......

JBuk · 19 Sep 2008 at 15:13

can you post an uncropped shot?

and one at 100% crop from a corner, or a link to a ful sized image?

Paul11 · 19 Sep 2008 at 15:25

is it possible to tell with out a tripod ? (dont have mine here)

here are without a tripod

http://www.paulross.me.uk/testpics/

Hodders · 19 Sep 2008 at 15:53

I was hand holding f4 and the shutter speed was 1/1000th so not too much chance of shake, f16 was at 1/16th which makes shake more likely.

But still interesting to see the images people get..

JBuk · 19 Sep 2008 at 16:00

you really need to do the test with a tripod but looking at those shots I would expect slightly better sharpness at the edges especially at f8 or smaller aperture

its not too bad though, certainly better than any of the copies I tried

D.P. · 19 Sep 2008 at 17:57

This lens is never sharp at 10mm or wide open or at short focal lengths. Then lens is much better by 12mm, f 5.6-8, and infinity focus. It wont perform good close up.

Photograph a landscape with a tripod at f/11. If you are happy then you have a sharp lens

Hodders · 19 Sep 2008 at 19:58

D.P. said:
This lens is never sharp at 10mm or wide open or at short focal lengths. Then lens is much better by 12mm, f 5.6-8, and infinity focus. It wont perform good close up.

Photograph a landscape with a tripod at f/11. If you are happy then you have a sharp lens

I agree totally with what you say, but I am a bit of a spod and do like measuring things and comparing them.

If the weather is OK this weekend I'll try to get out on my mountain bike and take some shots....

Youstolemyname · 19 Sep 2008 at 22:37

i am waiting for mine to come back from sigma in HK as mine was soft as sponge

Hodders · 22 Sep 2008 at 17:08

Youstolemyname said:
i am waiting for mine to come back from sigma in HK as mine was soft as sponge

How did it compare to the above ?

olv · 22 Sep 2008 at 19:03

If you don't know whether or not yours is soft or not then surely it defeats the point? I would ask if it is fit for purpose?

the Sigma 10-20 is not a sharp lens in general, it is acceptable in the majority of applications but seeing as though you dont get any decent DOF wide open at close focal ranges then there isn't imo much point shooting wide open.

What you really need to check for if you care, is sharpness left to right across the frame, as they can be soft on the left.

If it makes a difference, your crops look perfectly fine for 10mm and what I would expect compared to my sigma which is a decent copy, not that i've ever take a photo of a brick wall.