Do Fast Lenses Matter Anymore?

Started Feb 23, 2013 | Discussions thread
Teila Day
Teila Day Veteran Member • Posts: 4,432
Fast lenses can be night and day difference.

bruxi wrote:

As I look at pricing for Canon 70-200L lenses, it looks like the price premium for a 2.8 is about $1,000 (average of IS and non-IS versions). A thousand bucks seems like a lot for basically one stop when new sensors are bring many more times that through rapid ISO improvements (like the 6D). There is so much more room now on ISO to crank it up with very little performance drop off. The notion of "fast lenses" feels more and more like dinosaur film thinking and makes very little sense to me from a value perspective.

When I got a 5d2, I opted for the 24-70 f/2.8 instead of the 24-105 f/4 (typically bundled with the camera). There wasn't a question in my mind that I did not want the slower lens and I gladly gave up having IS for the increased aperture speed.

Testing an f/2.8 lens at a wide angle vs. a the same focal length at f/4 can be the difference between night and day depending on the background, etc. When I photograph someone with foliage in the background or kids on their elbows in green grass... both look less "choppy" when shooting at the faster aperture. The difference is also noticeable between a 300 f/2.8 and 300 f/4 lens.

You can of course experience the same difference with the 70-200 lenses. Whether it makes a difference to you will depend on what you shoot and how much shutter speed you need to coax from your camera... a full stop can make all the difference in the world, especially if you want to stay away from 6400 iso and higher which as far as I'm concerned is still an iso that I'd like to stay away from unless I have to go there.

It's not just about iso either, but also about the lens creating a gaping hole allowing you to focus quicker, see brighter, and lock focus on your subject in low light at times faster than a slower lens no matter what aperture you're using.

Use a 6x neutral density filter on a wide angle lens and try to focus on an f/4 lens vs. f/2.8 lens even though you're shooting at f/8 or so... that one stop difference can heaven to your eyeballs instead of fighting to just try and see your subject matter though the darkness of the filter or having to focus w/out the filter the screwing it back on. I like the luxury of being able to see the subject, quickly focus, and take the shot even with a (practically black) 6x ND filter on the lens.

There are so many uses for faster apertures that have nothing to do with iso

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