What would you do?

[BeckH]

I bought a Sigma 120-300 f2.8 EX DG and couldn't get a sharp image from it. I tried it on a 50D, a 40D and 1D mk3 and all gave soft (to be polite )results. I have a 100-400 Canon which was far better.

I bought the Sigma to use with a x2 converter for wildlife and used it with a solid tripod. I bought it second-hand and in desperation I sent it back to Sigma for servicing and any necessary corrections.

It came back 5 months later having been sent to Japan because Sigma UK said they couldn't sort it out here. They didn't say there was anything wrong with it, they just checked and adjusted the circuits.

And it is no better. 'Course it could be me, but I can get sharp photos with my other lenses.

Any ideas?

[anglefire]

No idea at all - I hired one last year and I found it a stunning lens, very sharp.

A couple of examples:





As for your problem, it seems strange that Sigma UK would send it to Japan if they didn't think it was a problem?

I don't know where you are, but is there anyone you know that could try it on their camera? If you are in the Midlands, I will gladly meet up with you and try it on my cameras.

[flake]

I'm expecting mine back on Monday from Sigma, although it had a very different problem, time will tell as to it's sharpness.

Often people say lenses aren't sharp, but don't say what they're photographing nor how they're doing it, and this makes it difficult to make an assessment of what the problem might be.

If you've been shooting high Iso at f/2.8 and the subjects are reasonably close then the depth of field might be shallow so focus is critical. Alternatively you might have been using low Iso and a lower aperture say f/8 on a tripod and have some motion blur.

Speculation of course because I don't know. Perhaps you might post a crop from a 100% image for us to see?

You've also said that you use it with the 2X TC, have you got the same results without it? Are the results the same at all focal lengths?

Can I suggest that you try the focus test normally used for microadjustments here This will at least tell you if the lens is focussing incorrectly, and by how much. You haven't actually said which camera you have but you might wish to trim the focus if it is out at all.

[adams1]

I have this lens. On it's own it's a great lens very sharp. I have tried it a couple of times with a Sigma 2x TC and have been really dissapointed with the results. Lack of sharpness, soft images. I havent tried it with a 1.4TC. Are you happy with the results using just the lens on its own without any TC added?
Andrew

[BeckH]

Thank you for your comments. I mostly take wildlife photos and crop quite heavily when for example I have been to my local wildlife haven at Titchfield in Hants on the shores of the Solent, like I did tis morning.

I am prepared to accept that I am doing something wrong as I was only charged £33.99 for the service. Sigma UK said it wasn't totally sharp so it was sent back to Japan and I waited from last August until 2 weeks ago to get it back. And it doesn't seem any different.

I do push my telephoto lenses quite hard, because alot of what I photograph is really too far away. My Canon 100-400 is the best I have, and gives the most predictable results.

I would let one of my friends try it but I think I will sell it on. Shame as it is in perfect condition. But awfully heavy.

Regarding which camera, I mostly use a 1D mk3, I have a 40D as back-up.
Angelfire, the shots you show are very good indeed. I will try and upload an image to my gallery.

[BeckH]

http://cdn.mos.photoradar.com/files/...shots-2009.jpg
This image is with the lens at just under 300mm f length, unsharpened. An image I could use I agree.


http://cdn.mos.photoradar.com/files/...shots-1987.jpg

This image is taken with the x2 converter and is soft. Again unsharpened. Both images have been cropped to around 66-70%
As you can see, I haven't quite got adding the photo correct. Sorry about this.
Regards Becky

[anglefire]

The first shot is pretty small - the second one tiny!!

Looking at the first one, it looks like the focus point is not on the bird, but a bit behind. The green netting and the gravell just behind looks to be sharper.

Have you tried a target and tripod to make sure that it is not back focusing? I find using the live view and the interferance pattern method works well. One article that looks to explain the procedure pretty well is http://www.northlight-images.co.uk/a...djustment.html

As for the lens being heavy - yeah it is! About the same as the EF300mm f2.8 L I also hired last year. And about 1kg less than your 100-400, which is a lot if you aren't used to it!

I hand held both all day and it was only the end that they were getting a bit uncomfortable - but then I've been using heavy gear for some time!

[KeithT]

It sounds like it went back to Japan to get re-chipped or something. One thing to note is that to get it calibrated by Sigma properly they will need to have your camera body. You can always test the lens yourself for front and back focus using this chart. I found it useful when checking my Sigma 50 straight from the box. http://focustestchart.com/focus21.pdf It's on the final or penultimate page if I remember, but the rest is worth a read as well.

[BeckH]

Thank you Keith, I spent some time reading the instructions through this morning.

I had wondered if the focus point was wrong but decided ir probably wasn't. I have decided to sell the lens and replace it with something I can have more confidence in.

Thank you all for your advice and suggestions.

Regards Becky