The Perceptual problem with f/4 lenses

Started Dec 4, 2012 | Discussions thread
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inasir1971
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The Perceptual problem with f/4 lenses
Dec 4, 2012

Lenses have up to now been marketed in such a way that we have come to equate fast with good. Not just with regards to the apertures, but with regards to every optical facet of the lens - from sharpness, contrast, to focus field.

This is probably why the 16-35 f/4 VR is (wrongly I think) for many a not well liked lens. It keeps getting associated with the 24-120 f/4 VR simply because they are both f/4. Maybe the decision to make it an f/4 lens was led by the desire to achieve other optical properties like flatness of focus field. Perhaps getting fast, wide, and flatness of focus field into one lens is like squaring the circle. So for a lens that is primarily used stopped down to f/5.6 or smaller - why not if that is the price of a flatter focus field and no focus shift?

I happen to think the 16-35 f/4 is very good. I also have the 14-24, but I think the 16-35 is better in part of the overlapping range. There are qualities other than aperture and it may be necessary to make sacrifices that in order to gain elsewhere.

Qualities such as size and weight, flatness of focus field, color correctness, distortion, minimum focus distance, VR...

When such lenses are made - such as the 16-35 f/4 VR, now the 70-200 f/4 VR, and possibly future lenses such as a high performance 24-70 f/4 (VR ?) - they confuse us. It's difficult for the company to signal which is the better lens because now faster does not necessarily mean better, it's just different.

For consumers used to 'f/1.4 is better than f/1.8', life is no longer that simple.

Look at the confusion that Canon's new EF 24-70 f/4L IS is creating. It is priced well above what the EF 24-105 f/4L IS is yet covers a smaller range and they are both constant f/4 IS lenses. The company can't very well come out and say that well the 24-105 is our crappy IQ lens and 24-70 is our good IQ lens. The reality I'm sure is that the 24-70 is a much better lens optically but try explaining that, let alone persuading people.

The new lenses are a good thing. It is just not so easy to change one's ingrained ways of thinking, particularly when it is the manufacturers themselves who taught us to think this way in the first place.

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