# Fast lenses may be  a waste of money and light...



## jaomul (Apr 10, 2013)

if this article from DxO mark is to be believed. High res sensors don't get the benefit below a certain f-stop (sorry if this has been done before, it is not a new article)

DxOMark - F-stop blues


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## amolitor (Apr 10, 2013)

As near as I can determine, you're still getting more light, just not as much as the increased aperture would suggest. So that benefit remains, but it's reduced. Of course you still get the imaging properties of wider aperture.

There's a bunch of reasons for fast glass, increasing the amount of light on the sensor at the widest aperture is just one of them.

The main one, of course, is looking cool, and that seems to be unharmed here.


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## jaomul (Apr 10, 2013)

amolitor said:


> As near as I can determine, you're still getting more light, just not as much as the increased aperture would suggest. So that benefit remains, but it's reduced. Of course you still get the imaging properties of wider aperture.
> 
> There's a bunch of reasons for fast glass, increasing the amount of light on the sensor at the widest aperture is just one of them.
> 
> The main one, of course, is looking cool, and that seems to be unharmed here.



I am not sure if this article really effects in the real world outside lab conditions, but another benefit is most lenses are a little sharper stopped down, so a canon 50 f1.4 should in theory be sharper at f2 than say a canon 50 f1.8


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## Overread (Apr 10, 2013)

Interesting results and the suspicion that the camera is raising its ISO sensitivity in the background of its operation is interesting. However its important to remember that this study is only looking at the pure light gathering properties of the lens itself and that the stated ISO raises were only to the order of at most 1/3rd of a stop of ISO. As such we are still seeing a lot of the gain (the other 2/3rds) coming from the lens's native light gathering ability (assuming a 1 stop difference between two lenses of the same focal length and different maximum apertures). 

Further the article is ignoring other properties of wider aperture lenses such as the typically present improvements in lens coatings - lens construction - AF speed - optical formula etc.... As well as the properties of increasing the aperture with respect to background blurring and depth of field - these latter properties being things that can't be gained in any other way than using a wider aperture*



*editing can potentially be used, but can prove to be very complex and time consuming to get to a similar level of quality and without an odd appearance.


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## 2WheelPhoto (Apr 10, 2013)

At dark indoor ambient only allowed events I use the fastest available no matter what the benefit or lack of benefit.  I don;t need to debate or crunch numbers or validity. The better the lens, the less ISO I need to employ


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## Derrel (Apr 10, 2013)

I looked at the article and noted with some dismay that the "newest" sensor technology advanced are missing...the majority of the Nikons listed were all introduced in 2007, or earlier, like the D3 and D700. Since then, I am positive that sensor technology from Nikon and Sony has made absolutely HUGE advances, especially at higher ISO shooting. The article mentioned that camera makers seem to have programmed in an automatic ISO level boost when lenses reach WIDE f/stops...well...that might have been an issue on the older sensors like those on the test list. with the two best, newest Nikons the loss appear to be either .3 or .4 EV, but with the "old" sensors, like those in the D70 and D40, the loss was around .8 EV.

"Ehhhh"...the newer, full-frame Nikons (and other cameras that use SONY's newest sensors) have utterly AMAZING ability to recover shadows, with almost no significant penalty. Like the Pentax K-7's ability to be shot at an f/stop and shutter speed that is the exposure equivalent of ISO 50,000, when the baseline ISO value of ISO 200 is actually set, on the camera, and then the resulting *100%* *BLACK FRAME *raw image can be "lifted" in software to make a good image. Not a "great image", but a good, usable image. I dunno...two weeks ago, I shot my D3x at ISO 1,000 in daylight, trying to add some "grittiness" to an image of a smooth-surfaced bronze statue. Didn't work...the images looked smooth and virtually noise-free. Very,very close to my ISO 200 images. 

What that article focuses on is severe loss of light on OLD-sensor technology, and what is misses is relevance to the NEW-generation cameras, where we have such incredible HIGH-ISO performance that the loss of 3/10 of an EV in T-stop is not even noticeable to most people. We do get the reduced depth of field and the subject isolation, but nowadays I am shooting with a camera where I have all the ISO I need, in reserve. So Nikon might bump the ISO up a bit when I open up past f/2...I seldom shoot there anyway. The article never did gain much traction in the three years since its publication. I can see why.


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## DistantSubject (May 15, 2013)

Hmm... I was going to make my next purchase a prime 35mm lens, but now I'm not so sure.  If there's not much improvement below f4, then why bother?  I'll just buy a better telephoto lens instead.


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