Sigma 30mm f/1.4 EX DC review

DrJim

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9 Mar 2006 - 10:59 PM

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Just a moment ago, I read the review of the Sigma 30mm f/1.4 EX DC review on this website (found here). A few things I read and saw made me wonder. Firstly, it is claimed in the review that:
Quote: CA (Chromatic aberration) has been eliminated to all intent and purpose. Shooting against a clear sky and blowing up to 400% showed no evidence of any fringing from f/2 onwards.

However, in the sample picture of the harbour that is provided to illustratethis quality (seen here) you'll find fringing that makes my Nikon 12-24 green with envy (enlarge the image to 100%, scroll all the way to the right and check the top part of the mast against the white sky). Moreover, the other image that is provided to illustrate the optical performance of the lens (seen here) is unsharp (I suspect this to be motion blur) and not very useful to judge the optcal performance of the lens. I would like to propose that this review be redone, because as it is, I do not find it very helpful.

Regards,

Francois Hendrickx

dark_lord

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9 Mar 2006 - 11:31 PM

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Those images are 3070x2046, the size I got from my 300D (C1 LE seems to lose 2 pixels off each dimension somehow unlike Adobe camera raw), hardly downsized. Obviously jpg compressed, but on a high quality setting as the file size is large. Good enough to download and print yourself.
I agree about not making ultimate quality judgements, but (a) its much better than the 'example enlargements' printed in magazines. And the second image is soft.

mattmatic

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10 Mar 2006 - 12:11 AM

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Yes, I see it as fringing on the edges. The centre looks ok, but all the edges show the fringing - either purple or green.

Doesn't look like sensor issues to me, especiallly if out of Capture One.
Matt

IanA

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10 Mar 2006 - 1:30 AM

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Hello Francois,

Welcome to ePhotozine.

Firstly the 'CA' that you have pointed out is a blue rope running down the mast. That is certainly what it appears to me, having just looked at the RAW file again. It is, however, only about 1 pixel wide.

The statement you have highlighted was made after assessing the full size picture of the Lifeboat seen in the review along with the results of bench testing and putting the results through Imatest. At no point do those result exceed the acceptable parameters set out by Norman Koren.

The other shot was taken, according to the exif, at 1/4000sec at ISO100 and f/1.4, so, even if the camera was set up on a pendulum, it is unlikely to have motion blur!
As stated in the review, the lens is softer at the wide open aperture at which that shot is taken.

The two shots that you have highlighted are compressed jpgs, normally compressed to around 50% in photoshop to give an idea of the quality of the lens without murdering the site's bandwidth. As Krimage has pointed out, they are still a better representation than shots in a magazine.

Should you want to investigate the findings further, I would be happy to send you the RAW files of both these shots and the Lifeboat shot from which I made the statement. Drop me an e-mail.

I hope this helps.

Ian

IanA

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10 Mar 2006 - 2:43 AM

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Hello Francois,

The two images are standard shots that are posted for every lens I review and are chosen for exactly the reasons that have arisen your interest, that they will show up any weaknesses.
I don't take just the shots shown and in fact used the lens for about a week for my own general photography. As stated in the review, I was happy with it and was sorry to see it go.

At Focus recently, I was asked about my reviews and stated that I take them seriously, realising that any comments I make are likely to influence what you, the reader, spends your hard earned cash on. Therefore, should I make a recommendation, it is one I truly believe.

The only instruction I have been given by the editor is to be honest and, short of being slanderous, that is what I do.
If you read my review of the 12-24 that you mention, you will see by comparing the two articles that my findings are similar to yours. And remember that that lens is three times the price, price being one of many people's major considerations.
I often get e-mails asking to expand on areas of reviews, something I readily answer where more specific details are required.

Ian

strawman

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10 Mar 2006 - 3:06 AM

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Ian/DrJim I probably owe you an apology. When I right clicked on the harbour scene IE told me it was 1012x674. If I load it into elements it is in fact much bigger so must be something to do with the IE re-size.

I have a Vivitar lens that produces nice bright purple fringes of a few pixels wide, so I was looking for that sort of effect. The question is does the edge effect seriously impact the image as it looks to be 1-3 pixels wide where I can see it. Is this true. And if so given its nature, is it not as Ian states effectivley an non issue.

Canon's 50mm f1.8 is about that soft wide open but sharpens a lot as it closes. Why not expect the same from this lens?

strawman

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10 Mar 2006 - 3:16 AM

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It gives you the option. In some photographs you can use the softness. Also what level of softness do you notice when you print, and how much can you adjust as you sharpen or adjust contrast.

I often find with digital we go pixel peeping in to each pixel, where with film we would have just observed the print.

I took a photo at ISO1600, wide open on the lens. Zooming in it had noise and was a bit soft. As a slide in a competition it was commended with comments on composition not sharpness or noise. Fact is it looked like it was shot on ISO 400 slide film, and as a projected image 6ft tall it was sharp enough, at a 6ft viewing distance.