Wide angle zoom not as wide as fixed focal

shiang_wang1 · April 29, 2014

I recently acquired a new Nikon 16-35mm F/4. I did a comparison on my other wide angle lenses, a 28mm AIS f/2 and a 20mm AFD, and found out the zoom is not as wide as these fixed focal lenses when I set it at respective focal length (just slightly). I wonder if anyone else has similar experience and is this considered normal for this lens?

Thanks

ShunCheung · April 29, 2014

A lens' official focal length is measured at infinity. Did you focus to infinity and compare?

Dieter Schaefer · April 29, 2014

I doubt that the markings on the lens barrel are sufficiently accurate to make such a determination - except at the end points of the focal length range.

mag_miksch · April 29, 2014

28mm AIS f/2

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a very nice lens

simon_platt1 · April 29, 2014

Hi there

Don't worry about it.

Marked focal lengths on zooms are not precise technical specs, some lens reviews measure the precise focal length but it doesn't really matter as long as it is not a long way out.

Fixed focal length lenses are usually very close to the focal length marked on them but again there is still a tolerance which would show if you happened to compare two lenses at opposite ends of the tolerance.

Wouter Willemse · April 29, 2014

...except at the end points of the focal length range.

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Not even there, focal lengths are approximated, so I wouldn't be too surprised the 16-35 is actually something like 16,45mm - 33,7mm (just making up figures!). As Simon wrote, it's not precise technical specs, just a very close value.

mendel_leisk · April 29, 2014

I have a couple of Canon zooms, both 24 mm at the wide end. Shooting the same scene with both, both set to 24 mm, there's a definite disparity in field of view. I think of it like stated engine displacement: there some rounding involved.

rodeo_joe1 · April 29, 2014

Below is an extract from a Nikon Patent application dated April 25th, 2000. As you can see from the design specification this "28mm - 200mm f/2.8" zoom was never intended to be exactly 28-200mm, nor the aperture a true f/2.8. This is pretty typical of zoom designs, and even primes are usually a bit longer or shorter than their nominal focal length. For example: The patent spec of Nikon's 13mm extreme wideangle states an actual design focal length of 13.2mm - not far off, but still not exactly 13mm. Add the effect of Infernal Focusing away from infinity, and the true focal length of a zoom lens is almost a complete lottery!

shiang_wang1 · April 29, 2014

Shun, it is indeed focus in infinity and on tripod.

Guys, thanks for your responses, they are kind of what I thought, I just need to hear them.

16-35mm is really a nice lens, I will be selling my 20mm but keep the 28mm.

Dieter Schaefer · April 29, 2014

Not even there, focal lengths are approximated

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I agree, all I meant to say is that at the end of either end of the focal range you know where you are; there is no room for error with setting the lens(as opposed to setting the lens to the 28mm marking which isn't well defined) - didn't mean to imply that 16 or 35 at either end are indeed that.

Wouter Willemse · April 30, 2014

Dieter, sorry, it wasn't meant pedantic, but more to underline the lack of "absolute" values throughout.

Mike_R1664876643 · May 4, 2014

Shiang, I just bought the 16-35 f/4 myself, and in comparing it to my 16-85VR DX, and it's not as wide at 16mm as my 16-85 on a DX camera (D300s). There is about a 1mm difference, which sort of surprised me.

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Wide angle zoom not as wide as fixed focal

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