Is this normal? Sigma 35mm F1.4

lodious

lodious

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Just taken delivery of Sigma 35mm f1.4. While reviewing some test shots, I noticed a colour shift (?) round the point of focus when wide open (see the Gain and Master 'white' text in the image below). Is this normal for a wide aperture lens? It disappears at f4.0.

http://flic.kr/p/ikSP9f

I love the lens, so I'll be disappointed if it has to go back :-(
 
It's normal for fast primes used at their wider apertures.

It's called "Longitudinal Chromatic Aberration" or bokeh fringing. All my primes do this to some degree on high contrast areas around the point of focus.

So enjoy your new lens!
 
Looking at the first photo, I thought it may be the lens. I had the same problem on a sigma when using it wide open and the whites were slightly over exposed. Then I saw the other photo, the one with the Marshall stack, and it appears on there too. Also the fringing appears on the texture of the amp covering. It's almost as if there are Xmas tree lights reflecting of it.
I'm not sure I'd be happy with that at all.
Is there anyway you can do a more controlled test??
Dean
 
Thanks guys, I googled "Longitudinal Chromatic Aberration" and saw quite a few similar test shots (like this one http://www.dpreview.com/forums/post/41683832) , so it looks like it's ok.

I love this lens! The focus is bang on without any MA tweaks, and it's so sharp. Really enjoyed using it this weekend :-)
 
Pretty much every wide aperture prime Ive ever had has done funky stuff to text when inside testing the lens out, but get it outside in the real world and they come alive.
 
Thanks for the reassurance TCR. Here's one I took in the real world to show I didn't spend all weekend photographing white text on a black background ;-)


2J8A0332.jpg by Lodious, on Flickr
 
That looks normal, but perhaps you wouldn't use it for near macro subjects... 100mm macro L hardly shows anything like that in comparison. You can fix it in Lightroom if you wanted.
 
OK Thanks, How would you fix it in lightroom? I tried the 'Remove CA checkbox', but it didn't appear to make any difference?
 
You also need to move the sliders underneath the check box, 'Defringe amount' which has purple and green sliders for the respective fringe colours.
 
Last edited:
Got it. Thanks! Is there much danger of it affecting the rest of the picture?
 
Interesting effect. NICE AMP. ;)
 
lodious said:
Got it. Thanks! Is there much danger of it affecting the rest of the picture?
Click to expand...
No it shouldnt affect the rest of the pic :thumbs:
 
All wide aperture primes do this on very high contrast scenes, enjoy your news lens, it's awesome.
 
Along with the suggestions on handling CA already given, you can also drag the purple and/or magenta colour sliders in LR down to zero, as there's no need for them in this image. That'll also help remove the purple, obviously.
 
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