Sony FE 100-400mm f5.6-8 OSS is the most affordable 100-400mm lens for the E-mount
Sony just did something I did not expect. Three months after launching a 100-400mm that costs more than most people's entire kit, they have released another one that weighs less than a can of soup and costs $849.99 .
The Sony FE 100-400mm f/5.6-8 OSS is 654g. To put that in perspective, that is lighter than plenty of 70-200mm f/4 zooms, and it gets you to 400mm. There are now three Sony 100-400mm lenses in E mount, which sounds absurd until you look at what they actually cost.
Sony FE 100-400mm f5.6-8 OSS on Sony A7C II Camera
The specs
Weight: 654g (23.1oz)Size: 164.5mm long, 78.2mm diameter, 67mm filter threadOptics: 15 elements in 10 groups, two ED and two aspherical elementsAperture: f/5.6-8, nine rounded blades, stopping down to f/32-45Minimum focus: 1.13m at 100mm, 0.86m at 400mmMaximum magnification: 0.41xAutofocus: dual linear motors, tracking at up to about 120fps on the a9 IIIStabilisation: Optical SteadyShot with Active Mode, plus breathing compensationHandling: zoom lock, combined focus mode and range limiter switch, extending barrelPrice: $849.99, around 900 euros or 800 pounds
That 0.41x magnification deserves a second look. That is close-up territory from a 400mm lens, which makes it far more useful for dragonflies and small stuff than the reach alone suggests. And it takes a teleconverter, so 800mm is on the table.
Sony FE 100-400mm F4.5 vs Sony FE 100-400mm F4.5-5.6 vs Sony FE 100-400mm f5.6-8
Three 100-400mm lenses, wildly different money
Lens
Aperture
Weight
Announced
Price
FE 100-400mm f/5.6-8 OSS
f/5.6-8
654g
Aug 2026
$849.99
FE 100-400mm F4.5-5.6 GM OSS
f/4.5-5.6
1,395g
Apr 2017
about $2,499
FE 100-400mm F4.5 GM OSS
f/4.5 constant
1,840g
May 2026
$4,299.99
The new one is a fifth of the price of the new GM and a third of its weight . That is not a small gap, that is a different category of purchase. You could buy the f/5.6-8, a body, and a holiday, for what the constant aperture GM costs.
Here is the full spec comparison from our database, so you can see exactly where the differences land:
I wrote about the new F4.5 GM against the 200-600mm and 400-800mm back in May, and the conclusion then was that the GM is a specialist tool for people whose income depends on it. This new lens is the opposite end of that argument.
What you actually give up
Let us be honest about f/8 at the long end, because that is the whole story here.
At 400mm you are shooting at f/8. On a sunny morning that is a non-issue. In woodland at dawn, which is exactly when birds are most active, you are pushing ISO hard or accepting slower shutter speeds. Sony's autofocus is genuinely good at f/8 these days, and the a9 III tracking figure is impressive, but light is light and no amount of clever AF makes f/8 into f/4.5.
Good image quality especially at the center according to MTF charts
The other thing worth knowing is that it extends when you zoom. The new GM has internal zoom, which keeps the balance constant and is one of the reasons it weighs 1,840g. The f/5.6-8 has a zoom lock, which tells you Sony expects some creep.
Run it through our depth of field calculator and you will see the flip side. At 400mm and f/8 with a subject 15m away you get about 63cm of depth of field on full frame, or about 41cm on APS-C. Either is far more forgiving than the razor-thin zone you fight with on faster glass, which genuinely matters when a bird is walking toward you.
Who is this for?
If you already own the FE 200-600mm , this is not a replacement, it is a different job. The 200-600 is the lens I reach for when birds are the point of the trip, and I said as much in my hands-on review of it . But at 2,115g it is a commitment, and there are plenty of days where I would rather have 654g on the strap and still be able to reach across a lake.
Impressive Weather sealing for the price
This looks like the right lens for travel where wildlife is a maybe rather than the plan, for anyone moving up from a kit telezoom who wants real reach without a second mortgage, and for APS-C shooters, where it becomes a 150-600mm equivalent that weighs almost nothing.
It is not the lens for low light, and it is not the lens if you shoot birds for a living. It might be the most sensible telephoto Sony has made in years for everyone else.
Availability
Listed as coming soon at the time of writing, at $849.99 in the US. Given how quickly the 400-800mm sold out when that arrived, I would not wait around if this is on your list.
Gear mentioned in this post
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Written by Mel Adali
I have been shooting birds and wildlife in North Carolina since 2014, mostly with Sony bodies and long telephoto glass. I built and maintain the Camera Decision database, so the specs and comparisons here come from data I curate myself rather than copied press releases.
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