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Author Topic: Sigma 35mm F/1.4 Reviews - Vignetting Disparity?  (Read 5372 times)

EvilTed

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Sigma 35mm F/1.4 Reviews - Vignetting Disparity?
« on: January 15, 2013, 04:57:08 PM »
Anyone else see a large disparity in the lens falloff measurements of the Sigma 35mm F/1.4 in the various reviews?

The Digital Picture lists a horrendous 3.5 stops on FF @ F/1.4 and 0.7 @ F/16 :(

Others such as DxO say the vignetting is normal @ around 2 stop wide open.

The copy I had and returned was in the latter camp having average vignetting wide open but nothing that made me notice it.
The front focus problems, yes, but not the vignetting.

Maybe there is a wide variance in samples and the 3.5 is the worst of them?

ET

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Sigma 35mm F/1.4 Reviews - Vignetting Disparity?
« on: January 15, 2013, 04:57:08 PM »

Quasimodo

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Re: Sigma 35mm F/1.4 Reviews - Vignetting Disparity?
« Reply #1 on: January 15, 2013, 05:39:57 PM »
I also reacted on that point i Digital Picture review. I have not noticed vignetting when shooting wide open on mine.
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brad-man

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Re: Sigma 35mm F/1.4 Reviews - Vignetting Disparity?
« Reply #2 on: January 15, 2013, 06:12:05 PM »
Same here. Moderate vignetting on 5Dll (doesn't bother me at all), none on my 7D. Looking forward to an 85mm A series lens...

jeffabbyben

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Re: Sigma 35mm F/1.4 Reviews - Vignetting Disparity?
« Reply #3 on: January 15, 2013, 07:26:22 PM »
certainly noticed vignetting on my Sigma 35mm 1.4 but not anything like 3.5 stops.

pj1974

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Re: Sigma 35mm F/1.4 Reviews - Vignetting Disparity?
« Reply #4 on: January 15, 2013, 09:37:31 PM »
I've read a few reviews about the Sigma 35mm f/1.4 lens, and it seems to have a lot going for it (very sharp, great contrast, good build quality) - particularly for the price.  (As a side note, if Sigma produce a similar 50mm to the new 35mm... I might consider... I've read / heard too much about the previous Sigma 50mm f/1.4 AF issues / QC / decentring to 'risk it').

There have been some concerns raised for the Sigma 35mm's bokeh at certain settings, and vignetting.  I can't recall reading details in reviews about vignetting, but maybe 1 review quoted full frame (FF = generally much higher vignetting) - and another test was on an APS-C (crop) body.

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dr croubie

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Re: Sigma 35mm F/1.4 Reviews - Vignetting Disparity?
« Reply #5 on: January 15, 2013, 10:09:17 PM »
For all the sites that are giving different numbers, check out some of the vignetting figures for other lenses that they've tested and compare them.

I know Bryan at TDP standardises all of his stuff in a certain way, under identical conditions, and processes them from RAW identically in DPP.
How about the other sites? RAW processed, or JPG? DPP or Lightroom/DxO/whatever? Standard contrast curves, or boosted or flattened? With hood or without? Shooting a gray-card or white wall or the sky?
All of those variables are going to change how much vignetting you see (especially using raw vs jpg and the default contrast setting), and the numbers you get.

In short, I'd trust comparing TDP's reviews of the Sigma 35 to the 35L, and I'd trust comparing Photozone's reviews of the Sigma 35 to the 35L, for example (among the decent review sites, at least). But i just wouldn't trust comparing the Sigma 35 review at TDP compared to the Sigma 35 review at Photozone, because they'll both test lenses differently.
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EvilTed

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Re: Sigma 35mm F/1.4 Reviews - Vignetting Disparity?
« Reply #6 on: January 15, 2013, 11:19:21 PM »
You'll have to explain my ignorance of the physics involved but how can testing RAW vs. JPG have any effect on the physical characteristics of the lens optics?

I can understand if it were a Canon lens on a n 5D MK3, 1DX or 6D body with lens correction turned on, but I wasn't aware that switching between RAW and JPG can affect lens characteristics?

Please explain...

ET

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Re: Sigma 35mm F/1.4 Reviews - Vignetting Disparity?
« Reply #6 on: January 15, 2013, 11:19:21 PM »

dr croubie

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Re: Sigma 35mm F/1.4 Reviews - Vignetting Disparity?
« Reply #7 on: January 16, 2013, 03:15:34 PM »
It's not that it's changing the lens characteristics, it's changing the way the photo is presented.

Extreme case: take a photo of a wall, process it in DPP from RAW twice.
First photo, set contrast to +5. Second photo, set contrast to -5. They are going to have vastly different vignetting *numbers*, because the numbers are taken from looking at the *photo*, and the photos look different even when taken with the same lens.

Now, i'm not saying that any review sites do that on purpose. But say one takes in raw and dpp processes at 0 contrast, and the other one just uses the camera jpg. The camera could be set to +1 contrast by default maybe? or even if the camera says '0 contrast' in its Picture Style menu, that could be more or less than what '0 contrast' in dpp gives you? Or even some thoughtless reviewer pressed for time accidentally leaves the 'vignetting correction' on by accident in-camera?
I don't know, it's all possible. In short, as long as you trust a single reviewer to keep doing the same thing over and over with the same equipment, then their results are comparable to each other. (Even if you trust a single reviewer, sometimes things out of their control mess up. Bryan at TDP noticed a bug in DPP a while back, where he'd set noise correction off for his processing, but in certain cases it turned itself back on and invalidated a lot of his results. At least he noticed and has since gone back and re-tested all the affected lenses, I hate to think how long that took him)

For further reading, here is a well written article by Roger about comparing results between reviewers and sites. He's mainly talking about resolution numbers, but just susbtitute the word 'vignetting' and you'll still have the same idea.
Or read any review at photozone.de (at least in a Nikon review), you'll get the following warning:
Quote from: photozone.de
We're performing our vignetting analysis based on (uncorrected) JPEGs straight from the camera. The JPG engine of the Nikon D3x features a rather flat gradation curve, thus has a moderate contrast characteristic, resulting in comparatively low vignetting figures - the corresponding Canon figures are roughly 40% higher due to the more aggressive default contrast setting.

Were any of those Sigma reviews taken on Nikons? Or even if they were all canons, do the 5D2, 5D3, 1Ds3, 1DX all behave exactly the same? (I think you get the point by now)
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Re: Sigma 35mm F/1.4 Reviews - Vignetting Disparity?
« Reply #7 on: January 16, 2013, 03:15:34 PM »