A decentered lens contains one or more optical lens elements that are either moved or tilted from the principal axis of the lens. Such shifting or tilting of lens elements can potentially lead to blurring / softness of parts of the image due to divergence of light rays. While very slight decentering of optical elements can be observed in many lenses, especially on superzooms, severe decentering and tilting can render the whole image blurry, with the lens unable to achieve good sharpness across the frame.
When my article on field curvature was published a while ago, where I talked about how one could do a quick analysis of lens MTF data and determine if it exhibits any field curvature, some of our readers expressed interest in understanding how to read MTF charts. Since we talk quite a bit about lens performance and MTF data here at Photography Life, I decided to write a detailed article on the subject and do my best to thoroughly explain everything related to MTF curves, charts and all the verbiage that comes with them.
A fellow photographer recently asked me how much image degradation one would see with each Nikon teleconverter. As a nature photographer, I have been wondering myself about this for a while, but never had a chance to actually quantify what the image degradation figures would look like when using the TC-14E II, TC-17E II and the TC-20E III with Nikon lenses. I have been relying on field use and my vision so far and here is what I have thought about each teleconverter.
The Nikon TC-14E II is excellent. I have not seen it degrade image quality on any Nikon lenses to the level where I could see obvious loss of contrast or sharpness. I have used it with the 105mm VR, 70-200mm f/2.8G VR (the old one, as well as VR II), 300mm f/4 and pretty much on every expensive super telephoto lens. I take it with me everywhere and mine stays pretty much glued to my favorite Nikon 300mm f/4 AF-S the majority of the time – that’s what I use primarily for birding. When shooting with my Nikon 200-400mm, I don’t hesitate to use the TC-14E II, because it does a very good job sharpness and contrast-wise and AF stays accurate and fast. It is obviously the smallest and the lightest of the three.
The Nikon TC-17E II is a mixed bag. It works with many Nikon lenses, but it slows down AF and impacts AF accuracy. Not as good of a TC to be used with slower f/4 lenses, which includes the 300mm f/4, 200-400mm f/4 and 500mm f/4 lenses. I tried to use it with my 300mm f/4 and it makes the lens hunt a lot, especially in anything but good light environments. The same thing with the Nikon 200-400mm f/4, even with the latest camera bodies like Nikon D4. Because of this, I rarely use mine. On fast f/2-2.8 lenses, however, it does pretty well. It works great on the Nikon 70-200mm f/2.8G VR II and it does not disappoint with the 200mm f/2, 300mm f/2.8 and 400mm f/2.8 lenses.
The Nikon TC-20E III is much better than its predecessor (which was very disappointing with many lenses). I was pretty shocked to see it perform very well with the 70-200mm f/2.8G VR II (stop down to f/8 for best results), because the 2x TC was always known to be bad with zoom lenses. It works like a champ with the 300mm f/2.8 and 400mm f/2.8 lenses. On slower f/4 lenses, however, it is still pretty disappointing. It is unusable on the Nikon 300mm f/4 and 200-400mm f/4 lenses and while it will work with the 500mm f/4 and 600mm f/4 lenses, you will have to stop down to f/11 to get anything reasonably good and you will need to use one of the latest Nikon DSLRs like D4 that can handle f/8 lenses. Not a great setup for fast action, but could work for large animals from a very long distance.
Michael Tapes Design, maker of the highly acclaimed LensAlign Focus calibration system, has announced FocusTune, The Auto-Focus Software Solution for correcting DSLR body/lens mismatch errors and restoring maximum sharpness potential.
Why FocusTune? In a nutshell, FocusTune quickly and accurately identiﬁes the best AF ﬁne-tune adjustment setting to match a given lens with the DSLR’s body. While virtually every high-end DSLR is equipped with micro-ﬁne tuning adjustments, the manufacturers have left the users to determine the optimal ﬁne tuning for themselves. That’s why Michael Tapes originally designed LensAlign. And now with the super high resolution cameras becoming so popular, FocusTune is the clear companion to get the ﬁnest detail from these remarkable cameras. Originally conceived as a partner for LensAlign, the new product quickly took on its own identity, offering its highly accurate analysis capabilities as both a standalone tool and in conjunction with LensAlign MkII.
I think I got myself into a lot of mess! I don’t even know where to start with all this stuff:
From bottom left to right:
- Olympus E-PL3 with 14-24mm kit lens
- Nikon 1 J1 with 10-30mm / 30-110mm kit lenses
- Nikon 1 V1 with 10mm / 10-30mm kit lenses
- Sony NEX-5n with 18-55mm kit lens
- Nikon 1 Nikkor 10-100mm lens
- Sony Zeiss 85mm f/1.4
- Sony A65 DSLR
- Sony 50mm f/1.4
- Sony Zeiss 16-80mm
- Sony A77 DSLR with 16-50mm kit lens
It is painful to even look at this picture…
I got my hands on a brand new Nikon 400mm f/2.8G VR that I have been testing for the last week or so. This weekend I am heading out to Yellowstone to shoot bears, wolves and whatever else I might encounter. This should give me a pretty good idea about how the 400mm f/2.8G VR performs in various environments with and without teleconverters. Here is the Nikkor beast:
This thing is a monster! It is heavy, bulky and comes with a nice leather case that is probably worth a lot of money. Expect a full review with sample images from Yellowstone within the next couple of weeks. The lens will be mounted primarily on the Nikon D7000 and occasionally on the Nikon D3s.
Hopefully this review will be great for those who are looking at buying a long zoom to photograph wildlife. I will compare the Nikkor 400mm f/2.8G VR against the following lenses:
- Nikon 300mm f/2.8G VR II
- Nikon 300mm f/4.0 AF-S
- Nikon 200-400mm f/4.0 VR
It would be awesome if I could do a comparison against the 500mm f/4 and 600mm f/4 as well, but I currently do not have access to these lenses. If anybody has a 500mm f/4 or a 600mm f/4 and can lend those to me for a day (for the sake of science, LOL), I would do a full comparison of all these lenses at once. If you are in Colorado and have the lens(es), please let me know via the “Contact Us” page. I will mention you in the review and provide a link to your blog.