To kick things off, let me say there are no winners or losers. This is like a competition between toddlers at pre-school where everyone gets a prize. This isn’t a direct technical comparison between the two and it isn’t about proving you should buy one in particular. This is about guidance on how I made the choice between the two.

The Sony 70-200mm f/2.8 vs Sony 100-400mm f/4.5-5.6 is a common problem choice in cameraland particularly when it comes to sports. It’s not really as simple as putting a converter on the 70-200mm and putting them side by side, they perform differently with and without the converter. For me personally, the 100-400mm was my answer, but like anything, it isn’t the same answer for everyone, hence the reason this isn’t a one paragraph article.

When I was with Nikon, I had the 70-200mm with the 1.4x converter, when I was with Fujifilm I had the 50-140mm (75-210mm full frame equivalent) and the 100-400mm (150-600mm equivalent) so I had the option to evaluate both, although in the case of the 100-400, not quite the same focal length as full frame.

Why did I end up with only the 100-400mm with Sony? That’s what this is about:

Do you need a portrait lens?

One of the biggest questions to ask yourself is whether you need a crossover portrait lens. The 100-400mm is not a portrait lens, it’ll do portraits, but it doesn’t excel at them like the 70-200mm. The 70-200mm is an incredible portrait lens.

Everyone does portraits, so it’s a no-brainer, get the 70-200mm, right? Nope, if it was that simple, I’d have the 70-200mm. Like the 70-200mm is a better portrait lens than the 100-400mm, there are better portrait lenses than the 70-200mm, the 85mm f1.4, 85mm f1.8 or 135mm f1.8. If you have one of these lenses, the portrait advantage of the 70-200mm loses its value.

In my case, I have both the 85mm and 135mm so having another portrait lens wasn’t a priority.

Do you intend using the lens indoors?

If you intend shooting sports indoors, the 100-400 is an f/4.5-5.6 vs the f/2.8 of the 70-200mm. It doesn’t take a rocket scientist to realise the 100-400mm is going to be seriously outgunned indoors. The 70-200mm is a better choice if indoor shooting is a major part of your work, however, that being the case, you might even want to consider the Sony 135mm f/1.8 for indoors depending on the reach you need.

Reach and image quality is more important than most people think

One of the common mistakes people make is the assumption that 100-400mm = 70-200mm + 2x teleconverter. Technically adding the 2x converter will give you a similar focal range and reach, but technically isn’t the same as reality.

The problem with teleconverters is that there is no free lunch, and by that, I don’t mean the cost of the converters. Every teleconverter impacts a number of aspects of the lens: sharpness, autofocus and depth of field. For each of these, there are acceptable levels of performance degradation and I personally put them in the following grades (which may differ from person to person):

• 1.4x teleconverter – good, almost unnoticeable degradation and acceptable for most users.
• 1.7x teleconverter – okay, noticeable decline but still acceptable for some people.
• 2x teleconverter – heavy degradation in autofocus and sharpness. Not acceptable by my standards and I would honestly rather crop than use this.

Yes, I know people will point to awesome youtube videos where people tell you how amazing the 2x still is but the vast majority are Sony sponsored individuals who can’t really say it’s terrible.

Another thing to consider is that a teleconverter can also be added to the 100-400 so whilst the 1.4x may extend the 70-200 to 105-280mm, it also extends the 100-400mm to 150-560mm.

As a result, I would say that if you need more than 280mm on a regular basis, go with the 100-400.

How important is focus speed?

Let’s be clear, both the 100-400 and 70-200 are amazing from an AF perspective, but the 70-200 is amazing plus about 50%. The 100-400 will handle most sports with relative ease, but if the kinds of sports you are doing are likely to push any AF system to the limit and you don’t need the extra length, go with the 70-200mm…simply speaking it’s better, but you’ll still need a camera to match the performance speed so it’s something to think about.

Depth of field

It is possible to achieve a similar depth of field with the 100-400 as you can with the 70-200 but only as at specific focal lengths so it’s not a one size fits all. At 100mm the 100-400 is f/4.5 vs f/2.8 so at lower focal lengths, the 70-200 wins, but when you extend out to 400mm you will be getting the equivalent DOF. Let’s be clear, I’m not proposing the 100-400 as a shallow DOF portrait lens, just saying under the right conditions you could achieve similar outcomes. That said, the 70-200 is still a clear winner throughout the range.

If shallow depth of field and longer focal lengths are required, then I’d consider the 400mm f/2.8 if you have a gold plated budget and a Sherpa to carry your gear. For now, I’ll stick with the 100-400mm as I have neither.

Landscapes

Yes, landscapes, it’s not my scene but I’ve seen some amazing landscapes out of longer lenses. I think the Sony 100-400 offers more flexibility if you do telephoto landscapes. I think the extra range helps and when you stop down to f8, you’re going to battle to find many discrepancies in the sharpness.

Sharpness

If you are a sharpness Nazi, then the winner is pretty clear cut…the 70-200mm wins. It’s not to say the 100-400mm is bad, but the 70-200mm is simply better, it has a smaller zoom range which makes it easy for Sony to get it sharper. There are no free rides when it comes to lenses.

Conclusion

I’m not sure if this has helped, but as I mentioned, for me the winner is the 100-400mm but it won’t be the winner for everyone. It’s the kind of comparison that is likely to 50/50 depending on your requirements.