Nikon 70 - 200 mm F/4 with TC-20E III

 

Published 2013/02/26

The original 70 - 200 mm F/4 test page is HERE.

Introduction

We already know the Nikon 70 - 200 mm F/4 is a superb lens. Can we extend some of that goodness to a much longer focal length with a 2X tele-converter (TC)? Why would we want to do this knowing we lose two full stops and end up with an F/8? On top of it all, we know there will be some compromise in optical performance. TCs are known to work best on fast primes like the 300 mm F/2.8 and not so great on zooms. In this case, contingency and convenience are probably the best excuses for considering use of a TC. Imagine going on a long photo-hike where you don't want to pack a whole lot of weight and think the 70 - 200 mm will be all you need for the subjects you expect to find. But just in case, you slip the TC-20E III into a shirt pocket hoping for a half-decent 400 mm in case Elvis momentarily steps out of the woods a hundred yards ahead and 200 mm won't get the proof you need.

This page presents another brief field test of the 70 - 200 (at 200 mm except for final image at 150) using the TC-20E III to obtain 400 (300) mm at F/8. For comparison, in the first set of images the same shots are taken with the Sigma 150 - 500 at 400 mm. The Sigma is the subject of some controversy arising, I suspect, from some significant unit-to-unit variation in optical quality. I have one of the good ones and find it very good to excellent throughout its focal length range, particularly in the all-important center region. A long lens is usually purchased for wildlife or sports where the subject is liable to be small and centered and the corners less critical than, say, for landscape work.

 

Field Tests

Setup

Procedure

With each lens the subject was photographed as follows:

  • Centered in the frame (FX - Nikon D800).
  • In the lower left corner - a more extreme test than using long or short edge. This position is outside DX boundaries.
  • All images prepared from "Fine" JPEGs and have received a small amount of in-camera sharpening but all images treated identically.
  • Both lenses at F/8 which is the maximum the TC combo can achieve. At focal ratios higher than F/8 diffraction places a limit on resolution of detail when using the D800.

 

Comparison of Images

First, here is the full frame view of my boring test subject. Enlargements will be of the numbered switch assembly almost dead-center in this image. It's the black knob and there is a numbered plate behind it. All images have been resampled to 100 dpi and should appear at 100% if your monitor is running native mode. FWIW, this was taken with the legacy Nikkor "Q".  The original images are noticeably sharper than these.  

You will notice these images, of the same subject as used in the original test, will probably look better than the TC-unassisted versions at 200 mm on that page. That's because those images were only half the size to begin with (owing to 1/2 the focal length) and then had to be enlarged twice as much to approach 1:1 subject:image ratio.

 

If your monitor is configured for native mode resolution the following images should be approximately life-size or a bit larger.

All images in this first section @ ISO 1600, F/8

Nikon 70 - 200 + TC-20E III (400 mm) / Subject Centered 

 

Sigma 150 - 500 @ 400 mm/ Subject Centered  

 

Nikon 70 - 200 + TC-20E III (400 mm) / Subject in Corner

 

Sigma 150 - 500 @ 400 mm/ Subject in Corner

This image initially suggested some motion blur but re-takes (all on tripod) produced identical results. The Sigma has slight corner weakness on FX that F/8 does not cure.

 

Conclusions/Observations

  • First Set - Subject Centred: The Sigma just wins this for sharpness. Note how all the lettering is readable (if with some difficulty) but the Nikon TC combo can't quite manage the finest print. The Nikon combo does, however, demonstrate a somewhat greater dark/light separation.
  • Second Set - Subject in Corner: The Nikon combo holds up perfectly. It's just as good as the centered subject and contrast is retained. In fact, it might look even slightly better. The Sigma loses its center sharpness. It is now significantly less sharp than the centered Nikon image.
  • On the D800 the TC combo focuses quickly and accurately, even in poor light. This may not be the case on other Nikon bodies.
  • No noticeable CA or distortion introduced by the TC.
  • Being limited to F/8 maximum aperture is a real bummer but you can't have everything. The D800 has very low noise at high ISOs so that's an option for overcoming some of the TC speed challenge.

On my ratings scale the TC combo merits a strong "Very Good" (excellent 11 X 14 prints judged possible and maybe even a bit larger). (Without TC the 70 - 200 rates a high "Excellent" score ... even "Superb".)

Bear in mind that the subject is approximately life-size here so it's a rather extreme test: the full image would be over 3 ft. on the long side. The Nikon combo is the better all-round performer being quite sharp in the center and losing nothing in the FX corners. The Sigma is sharper in the center but falters in the corners. Note that the Sigma can open to F/6.3 at this focal length while retaining the performance shown here.

 

Recommendation

Using the TC-20E III with the 70 - 200 F/4 is not a completely ridiculous proposition. Optical quality remains very good (at least) across the entire frame but two f-stops is a lot to lose. As part of a lightweight compact kit the TC makes sense for dealing with that unexpected occasion when you suddenly need the long reach. I haven't yet tested with the TC-17E II but based on performance with some other Nikkors expect it would yield even better sharpness while almost doubling speed over the 20E. The 17E also costs a lot less.

The final shot below is one of a suite (others not shown) suggesting using the TC with 150 mm lens setting (for 300 mm EFL) results in no photographically significant image degradation although you still lose the two stops.

Here are snapshots of some ordinary things using the 70-200 with TC-20E III

The objective is not to demonstrate fine photography but that very good photos can be obtained in a variety of situations despite some drawbacks to using a TC. All images hand-held and taken from JPEGs.

Full Frame (in height), F/8, 400 mm, ISO 6400

Oxford college coat-of-arms. Indoor weak lighting. About twice life-size.

 

Full Frame, F/8, 400 mm, ISO 6400

House plant indoors. Strong back-lighting. About life-size.

 

80% Crop, F/8, 400 mm, ISO 800

Poor "Harry" showing a bit of red-eye (which I rather like) - flash used at night in front yard - range about 30 ft.

Although near total darkness, focus was fast and accurate probably because of good contrast betwen white fur and the background.

 

Full Frame, F/8, 400 mm, ISO 500

An exciting board gate - range about 30 ft. Outdoors - hazy sunlight.

 

Full Frame (in width), F/8, 400 mm, ISO 500

Garden hose coupler - what a great shot! Indoors - weak sunlight.

 

80% Crop (width) - Left side is exact corner of frame, F/8, 300 mm, ISO 320

At the carwash - range about 30 ft. Outdoors - hazy sunlight.

Note that lens/TC combo is now at 300 mm FL. Even upon very close examination this image is indistinguishable from unassisted 300 mm shot at half the range.

 

 

 

Best wishes,

JH

140