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I rented the recently introduced 400mm DO II to test its resolution against my 300mm II.  The bottom line is that the 400mm DO II is every bit as good as the 300mm II at comparable focal lengths -- and even a little better wide open -- and the 400 DO II is lighter and shorter and therefore easier to use.

Gear choices are purpose-based (and cost constrained), and I use lenses in this range mostly for birds in flight and as multi-purpose hand-held telephotos.  While the 300mm II is better optically than original version of the 400mm DO it replaced, it hasn’t been perfect either. It is heavier than the DO and is usually too short; a 1.4X extender is almost always attached -- unless there’s a 2X in its place.  So the new optically improved 400mm DO seemed worth a look.

Test Results

My 400 DO II resolution testing produced results that follow other reports on Internet.  To summarize, the 400 DO II is at its best at f4 and f5.6 and is a bit sharper wide open than the 300/1.4X.  After that they become about equal, as the included center crops illustrate, possibly with an ever-so-slight edge to the 400 DO due to its maintaining marginally better sharpness to the edge.  Comparing the 400 DO with 1/4X vs 300/2X, the 400 DO has a slight edge at f5.6 and after that they are very close, although the 300mm II may have an exteremely slight edge near the center.  The 400 DO II appears to hold its sharpness farther out toward the edges.  Neither is at its best at f16.  With the 2X attached, the 400 DO appears quite useable, resolving to the limits of the 1Ds MkIII sensor with only a slight loss of contrast, a distinct advantage in long range situations.

Note: the images that accompany the text below are 100% sized Jpegs.  All testing was done in native RAW.  Unfortunately, the process of moving from RAW originals to web Jpegs tended to minimize differences that are more readily visible in the RAW files.  Given that these two lenses are already close, it is sometimes difficult to see differences in the web examples.  Where there is doubt, the text is the final authority.

I also made some hand-held comparisons, in my back yard and at a local park.  Hand-holding for critical test purposes isn’t ideal, although the results are certainly real-world.  Images were structured  to be comparable by subject, distance, nominal focal length, aperture, shutter speed and ISO.  Examined at 100%, the outcomes mostly tended to follow the static test results, although it’s difficult to be precise with hand-held targets of opportunity.

The included hand-held samples, of a riding toy comparing the 300mm II with 1.4X extender and 400 DO II at f4 (300 on left, 400 DO on right), reveal a slight advantage to the 400 DO II.  The  advantage is small, and it persists, possible due to ease of handling for the smaller, lighter lens.  Significantly, there seems to be little contrast difference between the two.  This would appear to minimize one complaint about the original 400 DO lens.  Also, color rendition is similar, although the 400 DO II tends to render a little cooler (bluer).  However, this was only visible on white signs and was virtually undetectable on other subjects.

Conclusions

Both lenses are superior performers optically, bare and with teleconverers.  The 300mm II can be used with the 1.4X and the 2X extender with excellent results but is slightly better when stopped down at least one stop.  The 400mm DO II is every bit its equal at equivalent focal lengths, and is at its best wide open.  The 300mm II tended to even the score when stopped down two stops or more.  The 400mm DO II may have a slight edge into the extreme corners.

Another point worth noting:  Because the 400 DO is lighter and shorter, it balances closer to one’s body, and for me it was easier to hand-hold.   I had the subjective impression from the viewfinder that image stabilization on the 400 DO II was ever-so-slightly more effective.  400 DO II hand-held images tended to be a tiny, tiny bit better than those from the 300 II, possibly indicating an image quality advantage when it comes to hand-holding the lighter, shorter 400 DO II.

Test Methods

A word about testing.  My static setup consists of a 1DsMkIII, beanbag-weighted Gitzo 340, ball head, two softbox-mounted flashes fired remotely from the camera, mirror lockup, cable release with timer delay, and IS off.  The test range is in my basement, on a concrete/ceramic tile floor.  Care is taken to square up camera/lens with target.  Although the ISO 12233 chart is now widely used, I have the Edmund Optics USAF 1951 resolution chart; with it I can precisely compare each area of a lens.  Best of three images at each setting was chosen for comparison.

Unfortunately due to space limitations, beyond 300mm the entire test chart will not fit into a full frame camera image. Both lenses were tested at a constant distance from the chart, resulting in slightly different image sizes since focal lengths were not identical.  An alternative would be to adjust distance to achieve identical image scales.  This isn't possible in my case for lenses longer than 300mm, and in any case this approach reflects the way these lenses would typically be used in the field.  I suspect the difference is probably insignificant; at the best performing apertures and zones for both lenses, resolution was limited by the 1DsMkIII sensor and not the lens.

Caveat:  This was a test of one sample of each lens.  Lens variability is well known so potential buyers should consider the results accordingly.  However, it is worth noting that in almost all cases results were limited by camera resolution and not lens resolution.  Also, note that I have not posted an exhaustive set of test images.  A few samples are included, but this test was done solely so that I could determine how the new DO measures up against my 300 II, and it fulfilled that goal.  The good news is that my findings tend to track what others have found.

Final Thoughts

Regarding these lenses, there are trade-offs involved in choosing between the two.  The 300mm II is less expensive than the 400 DO II (neither is cheap!) but is longer and heavier.  Adding extenders slows autofocus, albeit producing a slightly longer focal length and with it a slightly larger image scale.  Best of all, the 300mm II is an f2.8 lens if that is important.  I will stay out of the great DO OOF specular highlight debate; it doesn’t occur often enough or distract sufficiently for me to care about.  It appears that with the arrival of the 400 DO II there are now two outstanding, equally viable short telephotos, depending on one’s perceived needs and preferences.  If I were buying from scratch I’d go with the 400 DO II, for my purposes.  Whether I’ll take the financial hit to trade out of the 300mm II is a question for serious soul searching (AKA consultation with wife/CFO!).

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