Nikon 1.8g's vs Sigma 1.4 Art Series

Started Aug 16, 2014 | Discussions thread
Stacey_K Veteran Member • Posts: 8,363
Here is why it matters.

digital ed wrote:

First, this is my opinion and is not meant to denigrate anyone who feels differently.

I have never looked at one of my images and felt "if only the OOF part was better formed the image would be better."

If you are going for a shot that requires subject isolation, (and remember, many times you don't get to choose the background..) THAT is where this matters. Harsh bokeh ruins the "3D" effect I am sometimes after.

The other important qualities I look for in a lens is the transition from in focus to out of focus. Some lenses have a very rapid/harsh transition from the focus plane with can make the dof appear even more paper thin. I'm not a fan of the "obviously only one eye is in focus at all" type shots. I like there to be a slow transition from the actual focus plane to where the image becomes really blurry. Like their ears don't have to be crisp, but they look weird if they are totally blurred out as well. Sure you can stop the lens down to avoid this, but then you also bring the background more into focus.

Below is an example of this transition from the 80-200 f2.8 (old 2 ring version). If the transition was harsh like the 50mm f1.8g's is, her hand in the foreground would be so blurry as to become distracting. Especially if it was choppy looking with double vision type bokeh. You would "see it" as being a weird optical defect. Instead, as this lens renders you just don't really pay much attention to it. A lens like this allows you to shoot it wide open without having to worry about "working around" it's defects. And I think we all can agree, this shot done at f8 would not have turned out like this for many reasons.

Someone else posted some 50mm f1.8g shots at f8-f9 saying they look OK to him and they do. What happens with a lens like this (with choppy bokeh) is you are either limited to a couple of aperture settings (F8-f11) or you are limited on what the subject foreground/background can be. Good lenses don't require you to work around optical defects and I'm willing to give up some pure resolution at the focus plane (especially in the corners) to get it.

Most of this stuff you will never see in a lens review (and can you even test for it, i.e. put a number to it?) or from shooting test charts. It's actually hard to put your finger on it but there is a reason certain lenses "rise to the top" over the years like the 80-200 f2.8 has (and the 105mm f2.5 etc.) and this stuff is the reason. People have known for decades these lenses produce pleasing images, well before anyone really bothered to analyze why.

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