Lenses Let Through Less Light

One trend we're seeing in mirrorless is that the transmission properties of a whole breed of lenses are getting worse.

First off, we have everyone designing zoom lenses that are slowly sneaking another third or two-thirds of a stop less light transmission at the long end. Instead of f/4-5.6 as a common aperture capability we now get f/4-6.3, or in the case of Canon's latest, even an f/4-7.1. What happened to f/3.5-4.5, Nikon? And where did f/4-5.6 go? 

Meanwhile, because vignetting can be "corrected" after the fact, I'm seeing lenses with more than two and in some cases more than three stops of light suppression at the corners. You can't perfectly correct vignetting to start with, and most of the makers provide "corrections" that are more like "this is what the lens would be like if designed it the old way." 

So out there in the fringes of our images when we zoom in these days, it could be f/16 land in terms of the amount of light that got through to our pixels. Wide open. 

Perhaps the camera makers don't think we notice this. We do. Even a really good image sensor isn't going to make my image corners pull out noise-free data if this trend continues. 

Ah, but it's only a third of a stop, Thom (or two-thirds in Canon's case). Funny thing is, we have plenty of enthusiasts who are begging for a third of a stop more dynamic range. Now they'll need two-thirds (or a full stop) to be happy ;~). 

Of course, these lenses are being foisted off on the less suspecting consumer, so what do we care? Oh wait, the Sony 200-600mm is an f/6.3 at everything past 300mm. So bird and athlete watchers now get a third of a stop less lens, too.  

Don't get me started about t/stops on these lenses, either. On some of the more consumer lenses I've seen some t/stop creep, too. 

I'm not a big fan of convenience lenses, which is where most of the lenses I allude to fall. But the practice is starting to encroach on focal ranges I might actually want to use. 

I've written it before and remind you of it now: a complete lens set consists of:

  • Fast primes (e.g. f/1.2 or f/1.4 these days, and 20mm, 24mm, 28mm, 35mm, 50mm, 85mm, 105mm)
  • Smaller, modestly fast primes (e.g. f/1.8, f/2, or f/2.8 these days, and 20mm, 24mm, 28mm, 35mm, 50mm, 85mm, 105mm)
  • Fast zooms (e.g. f/2.8 at 14-24mm, 24-70mm, 70-200mm)
  • Smaller, modestly fast zooms (e.g. f/4 at 14-24mm, 24-70/105mm, 70-200mm)
  • A couple of convenience lenses

What Nikon's 24-200mm f/4-6.3 and Canon's 24-105mm f/4-7.1 tell me is that they think they are going to be selling a lot of low-end full frame mirrorless cameras. Maybe. 

I find it amusing that the company that started the whole consumer convenience zoom thing, Tamron, has moved on from that original 28-200mm idea to producing a set of f/2.8 zooms and macro f/2.8 primes for the Sony FE mount. Go figure.

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