Lens Sharpness and Contrast
If you have previously used a high-end 600mm f/4 lens, you already know what to expect – these lenses are designed to be remarkably sharp. But how much better can new optical designs be compared to their predecessors? As it turns out, quite a bit better. Since many of the older lenses were either designed for film cameras or did not take into account digital camera resolution, they tend to have more optical aberrations and quality control issues that can impact lens sharpness on a modern high-resolution camera. In comparison, modern lens designs are optimized for high-resolution sensors in order to deliver much higher levels of sharpness, and they go through much tighter quality control. As a result, sharpness differences in images are fairly obvious.
Let’s take a look at how the Nikon 600mm f/4E FL ED VR performed in our lab. Here is an MTF chart that shows the lens performance at different apertures, as measured by Imatest:
While a detailed comparison to other lenses, including the 600mm f/4G ED VR, is provided on the next page of the review, one can immediately notice how sharp the 600mm f/4E FL ED VR is, even wide open. I was surprised to see how sharp the lens is when shooting on the 45 MP Nikon D850, which is quite a demanding camera for any lens.
There is very little reason to stop it down – note how small the difference in sharpness is when going from f/4 to f/5.6. That’s how most photographers would use such a lens, only stopping down to gain more depth of field.
To get an idea of the sharpness potential of the lens, take a look at the below image:
And here is a 100% crop of the above image:
I did not see any focus shift issues on my sample, so testing the lens was a breeze.
Performance with Nikon TC-14E III Teleconverter
While all Nikon super-telephoto lenses are designed to work with 1.4 teleconverters, their performance can vary greatly from lens to lens. Lenses like the Nikon 400mm f/2.8E FL ED VR are well-suited for all Nikon teleconverters, but the slower f/4 and f/5.6 lenses often do not fare nearly as well. I have written about variances in teleconverter performance in the Image Degradation with Teleconverters section of the linked article, which goes through all the factors that affect sharpness performance with different lenses and teleconverter combinations. Let’s take a look at how the Nikon 600mm f/4E FL ED VR performed with the TC-14E III. With the 1.4x magnification and a full stop of light loss, the lens essentially becomes an 840mm f/5.6 lens:
As you can see, the Nikon 600mm f/4E FL ED VR did not do great with the 1.4x TC. Instead of a subtle drop of sharpness, I experienced a nearly 25% loss of sharpness when shooting on a 45 MP camera body, which is rather significant. Still, despite this sharpness loss, images are more than usable, since the lens sharpness is excellent to begin with. Bigger concerns when shooting with the 1.4x would be loss of light (f/5.6 max aperture), difficulty in framing a shot due to narrow field of view, and things like atmospheric haze, which can damage image quality further. But if it is a bright day and you don’t have such issues, then by all means use the 1.4x TC and don’t worry much about significant sharpness loss.
Performance with the Nikon TC-17E II Teleconverter
The older Nikon TC-17E II has always been a mixed bag when using with slower f/4 primes. Let’s see how it performed with the Nikon 600mm f/4E FL ED VR. The teleconverter robs quite a bit more light compared to the 1.4x TC, making it a 1020mm f/6.7 lens:
As you can see, the TC-17E II certainly impacts sharpness much more when compared to the TC-14E III. There is roughly a 35% loss of sharpness at maximum aperture. Stopping down to f/8 certainly helps a great deal though, so if you need the reach and you have plenty of available light without much atmospheric haze to deal with, then it is still a workable combination. Personally, I did not have much success with this combo due to autofocus reliability issues, but others report fairly good results. Since all lenses and teleconverters couple differently with each other, sample variation could be at play here.
It is important to note that if you shoot with a low to medium resolution camera (up to 24 MP), then the sharpness loss of TC-14E III and TC-17E II won’t be as obvious.
Performance with the Nikon TC-20E III Teleconverter
The Nikon TC-20E III is a fairly extreme case for the 600mm f/4 because it makes it a 1200mm f/8 lens – a bit too long and too slow of a combo. I personally found the two to be unusable, but if you are curious about the sharpness loss, here are the Imatest results:
Shooting wide open is not a good idea, because there is a clear loss of sharpness in images. Stopping down to f/11 brings some sharpness back, but diffraction is a huge factor at play here, and that’s what essentially destroys the image. Plus, you would need to really slow the shutter speed down or drastically increase ISO to be able to work with an f/11 lens – not great for shooting fast-moving subjects in low-light!
One of the strengths of long telephoto lenses is the beautiful, creamy bokeh they are able to produce. At such long focal lengths, you are also dealing with background objects appearing much more out of focus and closer, allowing subjects to stay beautifully isolated from the background. Just like its predecessor, the Nikon 600mm f/4E FL ED VR is excellent at this – it produces exceptionally good-looking background blur, whether you shoot wide open or stopped down, thanks to its 9-blade rounded diaphragm.
When it comes to vignetting, there is a little bit of light fall-off at maximum aperture when shooting at infinity, as can be seen from the chart below:
There is a little over 1 EV of light loss in the extreme corners at f/4, but stopping down to f/5.6 halves that, and if you stop the lens down even more, it basically disappears. Personally, I see no reason to shoot with a 600mm f/4 lens at infinity, so the only relevant numbers are at close focus range (which are more than acceptable).
If you are bothered by vignetting and you use software like Lightroom or Capture One, simply enable lens corrections, and the issues should be taken care of automatically.
Lateral chromatic aberration is under control, showing less than a pixel of it at large apertures, as can be seen from the below chart:
The above chart also shows the effect of teleconverters on lateral chromatic aberration. As you can see, it increases quite a bit with each teleconverter, reaching up to 4 pixels with the TC-20E III.
Ghosting and Flare
There is a reason why Nikon supplies such large hoods with its super-telephoto lenses. That’s because telephoto lenses generally do not do well with the sun or other bright objects reaching the front element of the lens. So, if you shoot against the sun, you might get some large, nasty flares and plenty of ghosting, which is quite normal. The integrated Nano and Super Integrated coatings certainly help in reducing ghosting and flare, but they do not eliminate it. So keep this in mind when shooting and avoid pointing your lens at the sun – you can actually get blind from doing this because everything is so magnified.
Distortion is usually not a problem on super-telephoto lenses. Imatest measured roughly 0.3% barrel distortion, which is something you would never notice in your images. Plus, I seriously doubt you would be shooting any straight lines with this lens. Distortion is generally not a problem, because it can be easily fixed in Photoshop or Lightroom using the Lens Correction module.
Let’s move on to lens comparisons.
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