Soft copies of lenses?

bandgeekndb

Over the past year, I've done a few purchases from DGrin here, and 2 of them have been Sigma lenses.

I'm trying to decide whether my lenses are suffering from mechanical problems, or if it's a problem behind the camera . What's making me think of this are extraordinarily soft shots at f/2.8 on my 18-50 f/2.8 EX HSM lens. While I'm at it, I'm also going to fully check out my 70-200 f/2.8.

First, how do I go about checking these lenses for problems, removing photographer error from the equation?

Second, if they are bad copies, do I have any recourse under warranty? I am not the original owner, but I believe I have original sales receipts for both lenses in my files, as provided by the original owners.

Third, if I have no warranty recourse, is Sigma still the best place to send it to, and about how much could I expect to spend? The lenses work fine, except for the softness at f/2.8, from what i can tell.

Thanks for all the info, I'm hoping my first few non-retail purchases weren't busts! I love the constant f/2.8, but I feel like it's unusable sometimes because of the softness. But, with such a shallow DOF, I know it is very likely that it's my fault too, so I want to be sure before I shell out for repairs.

Sincerely,
Nick

angevin1

The softness you mention seems to wend its way around the posts here every week or so. Why not post some photos for all to see and then make your case for what you feel ails the shots? Others here will chime in and tell you what they see and that can only help you in this.

Jeremy Winterberg

Also, for the tests, to remove user error... Use a tripod and set your camera to timer mode, or use a remote!

I think alot of people have been having problems with the Sigma 70-200 2.8... hence why I'm not going to purchase it anymore!

Also it would help people out if you told the exact model of the 70-200 because they have like 2-3 different versions.

Ziggy can vouch for the poor quality control of the sigma 70-200 2.8, I believe he went through 2 of them before getting the canon version...

Qarik

a lens sharpness test:

1) tripod
2) remote shutter release or timer release, shoot in raw
3) find a well lit controlled subject matter with a lot of detail (indoors preferably..no wind, etc)
4) start with lowest zoom and wide open. Select center focus point. Take a shot. increment the aperture till you reach f/8 or so
6) repeat at highest zoom
7) down load into imaging SW and inspect your shots.

All that said..that only gives you 1/2 the story. You have to shoot with the lens to see if AF is good in a variety of scenarios.

brecklundin

just rent or buy a LensAlign and be done with it. it's a tool to test all of your lens and camera setup for focus and IQ. They work great and should eliminate a lot of posts about this sort of thing because really, how is a person to know unless there is a tool to offer a reasonable reference...it will tell ya all you need to know and how to test your gear on your own:

Rent one here or buy from any nmber of places:

http://www.lensrentals.com/rent/lensalign

divamum

So glad I saw this thread!

Similar discussion here, which is also addressing user error vs lens problem (pretty certain in my case it's user error, but the discussion is relevant as you diagnose your own lenses)

bandgeekndb

Thanks for all the replies. I think tonight I'm gonna flip through my LR catalog and see if I have a few bad ones flagged, or if nothing else, try to recreate the soft shots.

I'll post back tomorrow with a few sample shots, and EXIF data of course!

Thanks,
Nick

zoomer

Not at all uncommon.
That is one of the reason people shell out big money for lenses like the Nikon 24-70 f2.8 and the 70-200 f2.8. The cost $1600. plus but at f2.8 they are sharp as a tack. (and probably their Canon counterparts)

Third party lenses and even some of the Nikon and Canon lenses will not approach the sharpness of these lenses at f2.8. There are a lot of lenses that are very sharp by F4 but not at F2.8.
There are very few lenses that are tack sharp at the extremes of their range.