[burncpt]

Hi all,

So in the spirit of Christmas I bought myself (!) the Sigma 10-20mm F/3.5 to go on my K3-II. I've had a few shots through it out and about and it seemed pretty disappointing so I tried a head to head with my old K-50 and a kit 18-55mm lens, and them swapped lenses and repeated at F/3.5, F/5.6 and F/8.

Each time I had the cameras on a solid tripod at ISO 100 and with a 2sec timer, at 18mm, RAW. I used the centre AF point.

Now I know there are still a bunch of variables but without fail, the images coming off the K3/Sigma combo were horrible, blurry like they were actually out of focus, and consistently much worse than the little K50 with its £100 kit lens.

Swapping over, the Sigma was able to do better on the K50 but it still, in my opinion was bettered by the kit lens. The best picture of the lot was probably the kit lens on the K3.

What's going on here? Is it a crap lens, is there a known issue with this lens on the K3II? Do I need to do something else to get anywhere near the performance of a cheapo kit lens (which considering the Sigma is marketed as a premium EX lens seems pretty poor).

Or is there an issue with my K3II? I haven't been very impressed with it generally over the K-50 - I was, perhaps naively expecting a significant boost in detail and resolution but most things look pretty average to be honest with other lenses.

Sorry for the long post but I'm pretty bummed and considering junking Pentax altogether if this is what the images off a 'flagship' £1000 body come out like.

Cheers

[awaldram]

Mmmmmm the k3 series is a fine camera that produces 1st rate images as many postings prove.

Equally the Sigma 10-20 is a very high grade lens from Sigmas top line range and again many posting from it show it is capable of very high detail sharp images on any Body inc all Pentax's.

Your complaints seem to indicate both the k3 and the Sigma are producing substandard results compared to your K50 and Kit lens ... I find this very peculiar and surprising.

There is either something wrong with your equipment, Settings or technique without further details its hard to define where the problem lies.

Could you post one of your 'Disappointing' images so we can see what is so upsetting in the results and perhaps diagnose the cause.

[boriscleto]

Did you try with LV? Did you try any focus adjustment at all?

[clickclick]

I think you might need a fine focus adjustment. I don't know that lens specifically, but most all lenses I have needed a tweak. A couple things to do. Try the test shots using Live View so it's using contrast detect for the focus. Also, use the self timer or a remote release with a delay e.g. 3 second on remote. Don't despair on the K3II. It's a great camera and capable of very nice images. I think you just need to sort a few things out to get dialed in. There's a good article on this site on doing fine focus adjustments here: Fixing Front and Back Focus - The Remedy - In-Depth Articles. Post back if you ned help on that. You can make your own targets to test on - basically take a page with print on it, angle at 45 degrees, focus on a spot in the center, and see if what's actually in focus is ahead or behind the spot you know you focused on. Adjust the fine tune in the camera then to either bring it forward or backwards as needed. The article goes into detail. I would recommend doing this, FF adjustment, for all lenses.

[Kombivan]

I have a 28-200 sigma that worked fine with analogue but hopless with DSLR hence I went to Tamron but saying this my images were worst to the sides, Bluriness is caused by too much light with depth of field so before you tak it back try a few test shots by stopping the lens down if it wants 11f give it 16f and 22f leaving the other settings as is also ensure you have lock in your iso at 100 for daylight if you want less shadows try 200 itmight be a light issue. and remember a 10-20mm comparing it to a 18-55mm is totally different just forget the 18-55mm and just inspect the 10-20mm on its own it should have a reasonable range of focus and have a read of the owners manual and see what the limits are for that lens because if you take it back the camera guy won't want it back so have a good study of it first so you know what your talking about if you take it back.

I learnt somthing new you can adjust the Focus for all lens or each lens you use.

[bm75]

My copy of that lens is really sharp. It was tack sharp with 12 mpx and someway softer with 24 mx bur surely sharp. Was the SR on the camera off during tests?

[bm75]

This was with 12 mpx (sorry...Nikon camera). 3 exp. HDR edited in Lightroom.

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[burncpt]

Hi Guys, thanks for the feedback. Here is the k-3/Sigma image. I used Live view and centre-point focus, ISO100, F/3.5 @18mm (to give a reasonable comparison with the 18-55 at a similar focal distance)

Is there any point posting a photo when the maximum file size is 1MB? Surely any fine detail and the tiny size renders subjective judgment impossible considering it's a 25MB JPEG originally?

---------- Post added 12-19-17 at 02:02 PM ----------

Here is the worst one...

[kiwi_jono]

The pictures are not showing up?

Yes posting pictures is still useful. You can either link to a full size image or include 2 - one showing complete scene and one a 100% crop of say the centre.
Would be great to see the image focused with LV (+ crop at focus point).

I have a Sigma 10-20 f3.5 and find its generally pretty sharp (certainly sharper than the 18-55), however they are known for having fairly soft corners at 10mm (usually comes right by about 12mm). Mine is particularly sharp (across the frame) 15 - 20mm - even wide open. They even cover pretty much fullframe from 15-20 (although the corners are very soft).

[burncpt]

Here is the worst image...

[aurele]

Here is the worst image...

It's just out of focus.

Try focusing with Live View. If the picture comes out good, then the lens might need micro-adjustement.

Try focusing throught the ViewFinder, using more focus point (the focus point used maybe couldn't find a discernible pattern to focus on) : If the result is good, no adjustement needed.

[burncpt]

100% crops, slightly less contrasty one is the sigma/K3, brighter one K-50

[aurele]

Each time I had the cameras on a solid tripod at ISO 100 and with a 2sec timer, at 18mm, RAW. I used the centre AF point.

Was Shake Reduction off ? SR + Tripod = blurry because SR freak out.

[burncpt]

100% crop centre. You can see it's awful! The brighter image is the K-50/Kit

[aurele]

You can see it's awful!

It's out of focus. try focusing with LV to see if there is an improvement.