[VoiceOfReason]

I may try mine on some film this weekend to see how bad the vignetting will be. Has anyone else done this yet?

[Adam]

I may try mine on some film this weekend to see how bad the vignetting will be. Has anyone else done this yet?

I looked through the viewfinder with the Sigma on a 5D III at photoplus. At 18mm it's literally a circle in the center of the frame. There's vignetting at 35mm but it's borderline usable.

[lytrytyr]

I may try mine on some film this weekend to see how bad the vignetting will be.

If you're looking for a 31mm f/1.8 lens on film,
I'm sure there are better choices out there!

[Digitalis]

FYI - Lightroom 5.6 now has a lens profile for the Sigma 18-35mm f/1.8 in pentax K mount.

I looked through the viewfinder with the Sigma on a 5D III at photoplus. At 18mm it's literally a circle in the center of the frame. There's vignetting at 35mm but it's borderline usable.

On my lens testing bench the sigma 18-35mm f/1.8 is usable* at 32mm and up, on APS -H format it is usable at 24mm and above. On APS- C vignetting is easily visible at 18mm f/1.8


* if you don't mind nearly -4EV of vignetting at f/1.8 At smaller apertures the lens behaves, but on APS-H and FX formats you can't use the lens hood at all as it is exclusively designed for use on APS-C cameras.

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Last edited by Digitalis; 07-30-2014 at 10:57 PM.

[VoiceOfReason]

Definitely interesting to know this. I may not use it after all.

I do need to get a 72mm IR 720 filter and see how it behaves in infrared. Hopefully it doesn't hotspot like my 17-50 does.

[Digitalis]

I do need to get a 72mm IR 720 filter and see how it behaves in infrared. Hopefully it doesn't hotspot like my 17-50 does.

It probably will, there is a lot of glass in this lens.

[snipenekkid]

FYI - Lightroom 5.6 now has a lens profile for the Sigma 18-35mm f/1.8 in pentax K mount.

On my lens testing bench the sigma 18-35mm f/1.8 is usable* at 32mm and up, on APS -H format it is usable at 24mm and above. On APS- C vignetting is easily visible at 18mm f/1.8

* if you don't mind nearly -4EV of vignetting at f/1.8 At smaller apertures the lens behaves, but on APS-H and FX formats you can't use the lens hood at all as it is exclusively designed for use on APS-C cameras.

Maybe a different hood will work? I use those collapsible rubber hoods you find all over eBay and Amazon for $5-$7/ea on all my glass. I tend to use a size larger, ie. use a hood with a 52mm filer size on a 49mm lens or even 58mm filter size hood. My contrast and results are as good or better than the original Pentax hoods on my 31ltd, 43td, 15ltd, 35ltd, 77ltd lenses. I have not had anytime to play with my 18-35/1.8 yet but have 72mm & 77mm hoods for it...just no FF body on which to play. I guess my long winded point is maybe you can salvage a few MM by moving to a tad larger hood, say a 77mm? Plus the hood shape is different so it might even work with a 72mm hood. Worth a shot I would think.

But yeah, the only shortcoming of the 18-35/1.8 I noted when ordering was it is a DC build so APS-C only with the hope that if one is ever released the lens would work on it...then again I have my Amigos and 15ltd primes so no big deal if it didn't.

[dadipentak]

Went for a stroll along the Potomac. I didn't want to get weighed down so I only took two Sigmas--18-35/1.8 & 500/4.5 ;~)

[Gooj]

This was my very first Sigma, and I really enjoy using it plus the quality on the pictures have so far been great. Though sometimes the camera troubles to calculate the right exposure for the scene.
Some might think it's on the heavy side, but I have no problem with it.

However, QC is a question mark. My NEW copy came with a few dust particles(!?) sitting in the center of the glass inside, on some element between the K-mount and the aperture blades. The front element also had a few dust particles on it when I got it out from the box, which does give an awkward feeling.
The only other complaint now, would be that the Sigma front cover is a bit flimsy made compared with what Pentax puts on theirs. Might not be due to the mechanism, it's just that it's so light like a feather I'm afraid that a wind might carry it away if left out of sight.

Oh well, waiting to hear back from the vendor.

It wasn't dust.

My copy came from the factory with a scratch across one of the elements inside. Which is a bit barbaric compared with some dust.
However a new one will be shipped to me as soon as they're available again. Luckily the pictures doesn't seem to suffer from this hic up.

[Digitalis]

My Sigma 18-35mm f/1.8 has returned, but the news isn't good - the official sigma distributor and repairer here in Australia ( who I will not mention) had the lens for nearly a month and refused to do anything to it because according to them: there was nothing wrong with it. I was not amused to hear how they tested the lens on a K7 at ISO 400 35mm f/8 1/500th handheld *facepalm*. So I'm having to send my lens over to my favorite optics technicians in Sydney at my own cost to get the the lens stripped down and re-aligned, these technicians did excellent jobs on my Sigma, Nikon, Canon and Zeiss lenses over the years and they have indicated they are prepared to work on this lens.

So my comparison of the Sigma 18-35mm f/1.8 and the SCMP-FA 31mm f/1.8 Limited will be delayed by another week or so. (To be honest the FA31 has already won, mine was optically perfect - and hasn't needed to be serviced in 5 years.)

[distudio]

My Sigma 18-35mm f/1.8 has returned, but the news isn't good

Would they repair (the thought sends shivers down my spine) or replace the lens if you produced a certified third party report that the lens was in fact not performing as the MTF guides suggest?

[Digitalis]

I didn't really need to send them the test data from my testing bench - the issue was apparent from images taken in the field (I sent copies of these images to the repairer) that there was a problem with optical alignment. These problems were clearly visible on the rear LCD of my K5IIs. And the adelaide repairer refused to repair or exchange the lens. The optical technicians in Sydney have access to a modern testing bench that uses digital sensors and full spectrum light to analyze the performance of a lens - so there won't be any need to get a third party involved. If there is a problem they will spot it and correct it- but as always the cost is a high one...but I simply have no other choice.

[rawr]

they tested the lens on a K7 at ISO 400 35mm f/8 1/500th handheld *facepalm*

I am disappoint.
Surely they must have access to a higher class of lens testing and repair tech than that. After all, they have been distributing and servicing Pentax glass for about 40 years (and other brands like Sigma & Hasselblad for a long time too).

[Digitalis]

I suppose they don't think of pentax APS-C cameras as a serious professional tool. No surprises there.

[Edgar_in_Indy]

I've sent Sigma lenses in for service a few times here in the US to the Sigma USA headquarters in New York, and each time their service and results have been outstanding--a couple times for calibration and once to repair a 100-300mm f4. It's too bad that you have to go through a 3rd party for service.