Do we still "need" fast lenses ?

Started 6 months ago | Discussions thread
Erik Kaffehr
Erik Kaffehr Senior Member • Posts: 2,609
Re: Do we still "need" fast lenses ?

JimKasson wrote:

Sergio Subrizi wrote:

Considering we have:

sensors with incredible iso performances compared to films

in camera +- 5 stop VR

Auto gain viewfinder

I can only see a shallower depht of field when used wide open as great advantage

at the expense of weight and $$$ ( for the same level of quality)

Do I miss something ?

I'm on your side. I wrote this three years ago:

"Since the film era, both Canon and Nikon have offered a line of lenses aimed at professional photographers and amateurs with similar intent and deep pockets. One of the hallmarks of those lens lines was a constant (unchanging with focal length in zoom lenses) aperture of f/2.8 or faster. There’s the f/2.8 standard zoom trio: 14-24mm, 24-70mm, and 70-200mm. There are 14mm and 105mm f/2.8s, and 24mm, 35mm, 50mm and 85mm f/1.4s. Canon even has some f/1.2s. The big iron 300mm 400mm lenses are f/2.8. For very long teles, where f/2.8 gets to be ridiculous, cooler heads prevail and we have 600mm f/4 and 800mm f/5.6 lenses, plus the 200-400/4 zoom. CaNikon make slower lenses, of course, but, with a couple of notable exceptions like Nikon's line of f.1.8 lenses, they seem to be a couple of notches down in quality from the fast lenses. Tamron and Sigma seem to follow the same speed/quality philosophy as the two big camera makers for their full frame lenses.

Modern full frame sensors, such as those in the Nikon D810 and D4s, or the Sony a7RII, a7R, a7S, and a7SII cameras, have great dynamic range, and can operate superbly where there’s not much light. They are so much better in that regard than film or the old sensors that I question whether most lenses need to be as fast as they are.

I’ll stipulate up front that big apertures mean paper-thin depth of field, and sometimes that’s exactly what the photographer wants and needs to make the shot come out with a creamily out-of-focus background. But not all photographers ever need anything wider than f/4 to get the background separation they desire, and those who do don’t need it for every lens in their arsenal.

The drawbacks of working with lenses that are faster than necessary are manifold: they cost more, are larger and heavier, and are more prone to decentering when handled roughly. They’re more obtrusive in public. Slower lenses work especially well with mirrorless cameras, which, with the exception of the Leica SL, are smaller and lighter than their DSLR counterparts.

A while back I wrote a paean to the combination of the Sony 70-200/4 and the a7x cameras, comparing the combination to a Nikon kit that was more than twice as heavy, though one stop faster. Last spring I tested the Nikon 300mm f/4 phase Fresnel lens, and found it delightfully small and light, and not a bad performer. I didn’t compare it to the Nikon 300/2.8, but, had I done so, I think I would have found that the 300/4 was not as good a performer at f/4. I don’t think that Nikon was aiming as high with the stop slower lens.

I’ve recently started to use the Nikon 500mm f/4E. At 6.8 lbs, it’s 1.6 lbs lighter than the 400/2.8E, though it is 25% longer. While you’d not consider it a small lens, I think it unlikely that, as long as it’s at my disposal, that I’ll use my old non-VR 400/2.8, which weighs close to 10 pounds.

Since their pro bodies are so heavy, I don’t think it would make much sense for Canon and Nikon to rework their whole lens line with top-notch f/4 lenses in addition to the f/2.8 ones. However, neither do I think Sony would be smart to come out with a set of f/2.8 native FE lenses in addition to the current and future f/4 ones. They might cherry-pick one or two. If I were running product management at Sony, I wouldn't have recommenced they do that ginormous 35/1.4.

When Canon and Nikon finally get around to doing pro-level full frame mirrorless cameras, they should think about a line of great f/4 lenses to go with them."



My take is that there are photographers who need high quality lenses and photographers who need fast lenses. Those groups are different. But, there may be an union between those groups.

Action photographers need fast lenses that perform very well around the best point of focus.

Landscape photographers need lenses that perform well across the field at medium apertures. But landscape photographers seldom need large apertures, they can often afford to shoot at medium apertures.

Landscape photographers often carry equipment longer distances, so they may be served better with lighter lenses.
All things are not bad, though, just as an example, Canon had a 16-35/4L zoom that was pretty decent at reasonable weight and price. I own that lens and it is pretty d__n good, mostly.
Getting really great performance at f/1.4 aperture is quite demanding. To get rid of axial color, you need very expensive glass. AiryDiscuss who is a lens designer working with many system has calculated that the glass cost for the front element of the Otus 85/1.4 is around 500 $US. 
If we never use large apertures like f/1.4, buying $500 glass may not make any sense. Also if you don't spend on all that glass you may end up with a lot of magenta/green out of focus rendering. That may matter, or it may not.
But, I  would put a vote for small and well corrected medium aperture lenses.

Best regards


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Erik Kaffehr
Magic uses to disappear in controlled experiments…

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