Sigma 10-20 arrived, best way to test it ?

simonkit

simonkit

Suspended / Banned
Messages
4,240
Edit My Images
No
I've just recieved a new Sigma 10-20 & would like to make sure the lens is a good copy, would appreciate some tips on the best way of testing it ?

thanks

simon
 
take a photo of something like a brick wall or a sign in the left hand side of the frame, take the pic. enlarge it on PS then have a look at the left hand side and see if it is soft
 
Try and make sure the camera is exactly parallel to the wall and don't shoot at the widest aperture, stop it down to about f10 to give it a good chance to get the wall completely in focus.
 
Thanks everyone,

just tried the shot hand-held (had to shoot vertically & rotate on PC) - doesn't look very promising - R/H side seems very soft. I'll set-up the tripod now !!


[edit] Maybe I was a bit hasty with the handheld shot, here are 2 tripod mounted shots - 1st F11, second F8....

It seems to sharpen nicely at F11 - still a little soft at F8 though, what do you guys think, keeper or not ?

(click on thumbnail image & then again on "pop-up for full size, these are quite heavily compressed . jpg)










simon
 
I think your image is a tad big there Simon! and f5.6 isn't giving you much dof
 
Steep said:
Try and make sure the camera is exactly parallel to the wall and don't shoot at the widest aperture, stop it down to about f10 to give it a good chance to get the wall completely in focus.
Click to expand...

With all due respect, stopping down to f/10 is not much of a test of any lens. It needs to work well wide open, and even better stopped down.

As an example, at 15mm and f/10, for a subject 3' away, your DOF runs from 1.7' to 12.8'. Well that gives a pretty massive safety margin for focus inaccuracy and sharpness.

I would suggest trying some of the settings (aperture and focal length) listed here - http://www.photozone.de/canon-eos/3...-56-hsm-ex-dc-lab-test-report--review?start=1 - to put the lens through its paces. There's no need to go mad but I'd say nine shots should cover it - 3 focal lengths at three apertures each. Decent light, low ISO, a solid tripod and mirror lockup and remote release go without saying, of course :)

You can infer from the web page that things to look out for are distortion, vignetting, chromatic abberation and sharpness (at the centre, edges and corners). It's hard to check AF accuracy with a wide angle because the DOF is so huge, but there's no harm checking that things do look sharp when using AF, and for that to be effective you'll need to be wide open to get the narrowest DOF you can.

Taking things the extra mile, it is commonly said that a lens should be tested at distances that represent real world use, rather than a contrived environment. So, for example, if you're going to use the lens for landscapes then test its performance with the scene/subject some distance away. If you're going to use it close up for unusual distorted perspectives then test it close up (but make sure you are not closer than the MFD). In the absence of any specific intentions for use I've often read that you should test a lens at around 40X the focal length. So at 10mm FL you should be testing with a subject 40cm away and at 20mm your test subject should be 80cm away.

Just some food for thought.... :)
 
Ooh, I'd be definately interested to hear people's thoughts on this lens. I'm really really wanting to buy one.
 
simonkit said:
I've just recieved a new Sigma 10-20 & would like to make sure the lens is a good copy, would appreciate some tips on the best way of testing it ?

thanks

simon
Click to expand...

I prefer to go old school.

Throw it off a cliff, if it falls to the bottom and smashes to smitherines it was a good lens. If however it flies off into the distance, chances are you bought a duffer.
:bonk:
 
I had one, loved it, sold it to go full frame (I have a 30D now, temporarily until I get a 5D or 5D replacement, or go Nikon and get a D300).
 
It doesn't look bad there, a touch softer on the right side though. One solution if you're not happy is to send it to Sigma UK to get them to check it out for you, if they adjust it you can be sure you get a good copy back.
 
Steep said:
It doesn't look bad there, a touch softer on the right side though. One solution if you're not happy is to send it to Sigma UK to get them to check it out for you, if they adjust it you can be sure you get a good copy back.
Click to expand...


I have 2 options I guess - send it back to the supplier & get a refund or as you say send it to Sigma..

if I send it to Sigma I guess that if they can't do anything with it they'll send me a replacement ?

simon
 
If needs be Sigma will replace the glass in the lens, what they will most likely do is adjust the elements as needed to sharpen up the right hand side. Give their service number a ring and ask for more info about it.
 
It's up to you, but personally, I don't think it's too bad. I'd be surprised if you noticed it in the real world as most of the time You will probably be using the lens well stopped down for max dof. I'm not sure you'd see much improvement if you sent it back to sigma and you'll be without the lens for a good while whilst they tinker with it.

Mines a bit rubbish in many ways but it's never stopped me getting great photo's with it.

Alternatively, you could stick it on ebay and get the tokina 11-16mm which is massively better in every respect.
 
Thanks everyone for the advice/feedback on this one...

in the end I decided that it's no good having a lens which can't be used fully at apertures wider than F11 - I've sent it back to the supplier who is going to swap it for another copy, if the new one isn't much better then Sigma will be hearing from me

simon
 
Just a quick update on this one & a word of warning to others...

I placed the initial order with Bristol Cameras & have sent the defective lens back - unfortunately they haven't time to look at it for a full week so can't promise me a replacement until mid next week at the earliest... apparently they're short staffed etc etc...

anyway I've now asked for a refund instead & ordered a new one from SRSMicrosystems today, should have done this in the 1st place...new lens will be here tomorrow....

can't really recommend Bristol Cameras to anyone :thumbsdown:

simon
 
Sorry to hear you got a lemon. Hopefully the new one will live up to its deserved reputation as a great UWA lens.
 
Bit late, but as long as the lens is not a grey (which is won't be from Bristol Cameras) Sigma UK will just swap the lens over, and should take less than a week.

Sigma UK will fix AF problems or general repairs but for uneven softness they can't fix and send back to Japan. 9/10 you'll get a new lens back.
 
You must log in or register to reply here.
Back
Top