Best Olympus pro telephoto – surprising test results

The Olympus pro 150-400mm F4.5 zoom is described by many as the best telephoto lens ever made for wildlife photography. It costs an eyewatering £6500, however, and is not exactly compact. I have been contemplating getting it for several years. To finally decide, I did some extensive testing, comparing it to the two pro telephoto lenses I currently use. The results I got may surprise you.

Note: Olympus lenses have an equivalent focal length of 2x their actual length. So a 300 mm Olympus lens has the same effective focal length as a 600 mm full frame lens.

Olympus pro telephotos – what’s important for Birds in Flight

If you use the right lenses, Olympus cameras give nothing away to full frame cameras for birds in flight (BIF) shooting, and have many distinct advantages. The essential items to compete with FF super telephoto lenses are:

1. Very fast – at least 1-2 stops faster than full-frame long zooms
2. Accurate and fast focus
3. Light weight and small size to keep the lens inertia down
4. As crisp and sharp as a full frame lens

These criteria eliminate all the non-pro super telephotos lenses from Olympus and Panasonic. However, the two pro lenses I use for BIF, the 300mm f4 prime, and the 40-150 f2.8 zoom, perfectly meet all these criteria. The 150-400 (or BWL for big white lens) meets criteria 1,2 and 4, and compared to a full-frame zoom it is amazingly light at around 2kg, and around 30cm long. But it is significantly heavier than the 300mm f4 which is only 1.3 Kg and 22 cm long.

Moreover, the BWL is a physically big lens that requires a much bigger photo bag to put it in. But the shining benefit of the BWL is its incredible versatility and range, from 300-1000 mm in full-frame equivalent terms. So which way to go?

The deciding factors

I spent 18 months dithering on whether to spring for the BWL. Other than the weight and travel problems, a major issue for me was that it basically committed me to the Olympus/OMD system. I have always based my decisions on the best technology available, not just on brand loyalty, and for the same money as the BWL alone I could get a complete Canon (R5 and 100-500), Sony (A1 plus 200-600) or Nikon (Z8 plus 180-600) system. That’s a camera and lens for each brand.

So the key questions for me were does the BWL make up in focus accuracy and sharpness what it gives away in size, weight and cost?

Fortunately, a friend owns a BWL, and he generously lent it to me for testing over two longish periods. I present the somewhat surprising results of those tests below.

Olympus pro Focus accuracy

My favoured focal length for birds in flight is around 400mm (Olympus) or 800 mm (in full frame equivalent) as I outline here. To get to 400mm with my current lenses, I need to use the Olympus MC-14 which extends the focal length by a factor of 1.4 at a cost of 1 stop of light. The 300 mm plus MC-14 is then a 420 mm (840 FFE) f5.6 lens.

The reputation of the MC-14 with the 300 mm is a bit equivocal, as some say the extender really affects focus speed and accuracy and overall sharpness. I had tested this combination in 2021 at Bempton Cliffs shooting Gannets with my prior Olympus BIF camera, the EM1x, and the performance was very disappointing, as demonstrated by the table below. While the 300 mm alone gave a very high hit rate of 78%, when paired with the MC-14, it dropped by half. I wrote off this combination as a result, and was left still searching for a suitable 800mm option.

In 2022 I had the opportunity to return to Bempton using the new OM1 camera with its vastly improved focusing system. I had the 300mm and the BWL to hand, so was able to compare them. There were two standout results from these tests. Firstly the OM1 transformed the focus accuracy of the 300/MC 14 combination. In worse light than the previous year (see the EV rating measuring the amount of prevailing light – higher is brighter), this 840 FFE lens setup performed outstandingly. In fact, given the worse conditions and the much greater difficulty of shooting at 840 mm FFE, this performed at least as well as the prime lens had the previous year.

With that baseline result in mind, I then tested the BWL at 800 mm FFE on the OM1, expecting to get a much better result. To my surprise, it was around 10% less accurate. This was over 600 images for each lens, on the same camera in identical conditions with the same set of flying Gannets, and the results really surprised me.

Hmmm. So the Olympus pro BWL did not have superior focus accuracy at 800mm FFE. Presumably though, the image quality/sharpness was better. I needed to test that also, it seemed.

Olympus pro Sharpness tests

One of the shortcomings of lab lens sharpness tests, such as Imatest, is that the set-up places the camera quite close to the test chart. However, BIF shooting always involves the bird being a good way away. My goal was to measure the lens sharpness when the camera was far enough away that a normal-sized bird would occupy the same proportion of the frame as in the field. To do this, I bought an A1 sized ISO 12233 Resolution Chart, which is the industry standard for imaging system testing and provides a resolution up to 4,000 lines per picture height (l/ph).

For a long time, I mulled over trying to set up this rig outdoors so I could get the camera far enough away from the test chart. However, problems with wind and rain (in the UK) made this impractical. After a while I realised that the length of my hallway at home, plus the landing outside was around 20m, so as long as my opposite neighbour did not mind my rig right outside her front door (she didn’t), I could do the tests much more controllably at home.

The setup was as follows. The test chart was mounted on hardboard and set at one end of the corridor. I attached two feathers to the centre of the chart to test the ability of the lens to resolve this fine detail. The lens and camera were set up so that the test chart filled the screen for each lens. The lens was mounted on the tripod with its tripod mount. ISO was set to auto, and I set the shutter speed to get ISO below 400 for every lens. The lens was centred on the middle of the chart, and set to wide open. I did not rely on autofocus, but manually focussed using 7x magnify to ensure the focus was exact. I set a 2 second delay for each shot using a remote trigger to ensure the lens was steady. For each lens, I took a minimum of three shots and chose the sharpest of the three for evaluation. I tested up to 4 lens combinations for each focal length – e.g. for 300 mm, I tested the 300 mm prime, the 150-400 mm zoom at 300 mm, and the 40-150 mm zoom plus the MC 20 at 150 mm. All the lenses were mounted on my OM1.

For evaluation post-processing, I used ON1 PhotoRaw 2023. I used AI match to get all images as close to the camera standard as possible. I then cropped all images to exactly the same dimensions from markers on the chart (approximately 10 cm square) as shown on the left. To ensure the contrast was the same for all shots, I took the black and white points until just below clipping at each end.

The main question, having got all these data, was how to evaluate the lenses. Although the formal way is to evaluate the number of resolved line pairs, I have found this very subjective in the past. Instead, I took the best image from each lens and focal length, and compared them for sharpness – ie. compared a maximum of 4 photos per focal length for how well they resolved the lines and the feathers. I then ranked the lenses in order of sharpness. After I had done this, I asked the owner of the BWL to do the same so we had an agreed view. The results of this ranking are shown below from 150 mm to 600 mm (300 mm to 1200 mm FFE).

Wow – does this say what I think it does?

Well done if you have made it this far. If you have, then you may be a bit startled by the results I got. First of all, the 300 mm f4 was unequivocally sharper than the BWL at all focal lengths, even with the MC 20 attached. I should note that my friend’s copy was one of the earlier Japan-made models, which were hand-made and have legendary quality. The BWL is an astonishing lens still, but the 300 mm is more than a match for it in any combination based on image quality.

More startling was that the venerable 40-150 f2.8 pro zoom was as sharp or sharper than the BWL even with the MC 20 attached – an astonishing result. My mind was blown by these results.

Needless to say, I am staying with the 300 mm F4 and the 40-150 f2.8, despite the many advantages the BWL offers. There is no penalty in focus accuracy and no penalty in image quality.

Can everyone get these results?

Not necessarily. Before and during the tests, I went to some trouble to ensure I had good lens combinations. I am currently on my second 300 mm f4, with the first being noticeably less sharp, and my second MC 14, so copy variation plays a part here. However, with care and some testing, a superb level of image quality can be obtained from the Olympus Pro lenses and extenders. All my lenses are second user by the way, and I have noticed that the older the lens, the better the quality – although this may not be a golden rule as wear and tear also applies in the equation.

Should I dump my BWL?

Of course not. It is still the greatest wildlife lens ever made from any brand. It offers unparalled range and convenience. It allows shots to be taken at multiple distances, which would defeat the 300 mm f4. It weighs less and takes up less room than the 300 mm f4 plus 40-150 mm f2.8 plus the two teleconverters. If the second-user price comes down, I may still get one.

But for the obsessive photographer, the absolute best result is still to be obtained from the original Olympus pro zooms, with all their problems. And the shining benefit of these lenses is that they are tiny, super fast to move, super sharp, and super accurate. So they will do me fine for the duration.