Testing a lens...

[danmerkel@sbcglobal.net]

I recently purchased a Nikon 70-300mm VR AF-S Zoom lens. At closer ranges... say up to 100-150 feet, it seems plenty sharp. But at much longer ranges, it seems really fuzzy to me. Since I have poor eyesight, I rely heavily on the auto focus and that "may" have something to do with the problem I think I'm having. I'm using the lens on a D40x.

I'm looking for simple ways to test the lens based on the experiences you may have had with trying out lenses for the first time. I want to make sure that there's an issue as opposed simply to "operator error."

One other thing which I find puzzling... the lens has three switches on it. One is for Auto/manual focus, the second is for VR on/off and the third one is for VR Active/Normal. When I depress the shutter half way to get readings and to allow a/f to set itself, the lens makes a rattling sound (a/f on, VR/on active). I thought this was the VR kicking in but it continues to "chatter" like it's rapidly going on and off all of the time. I don't remember this being the case at first (I've had the lens about a month). Does this sound normal, especially at long ranges?

Thanks for your help.

dlm

[autofocus]

Dan, all lenses have sweet spots both in their aperture settings and their focal range. Very often lenses will fall off at, or near their extremes on both ends. And usually the sweet spot for the aperture is usually around two or three stops closed down from full open. As far as the noise...do you have your camera set for continuous focus, or one shot? If on continuous, it will constantly be focusing and re-focusing as you, your camera, or your subject is moving. So, it may not be you afterall...

[OsmosisStudios]

Can you show us some examples, preferably at 100%, to see this "fuzziness"?

[crocodilo]

I may be overstretching myself on this one, but at longer distances isn't the atmosferic refraction and amount of particles in the atmosphere supposed to make everything more difuse? Take a pair of binoculars, for instance. Maintaing the same magnification, a distant object will be diffuse and soft-looking, because the light has travelled through a lot of vapour and suspended particles. For this same reason, colours in the distance look much more faded than at close range, an effect most canvas arists are familiar with, and use this de-saturation to emphasize distance.

No wonder that all telezoom lenses loose sharpness at long ranges. This probably has got nothing to do with the focal distance, just the observer's range to the subject.

Just my two (euro) cents.

[autofocus]

Originally Posted by crocodilo

I may be overstretching myself on this one, but at longer distances isn't the atmosferic refraction and amount of particles in the atmosphere supposed to make everything more difuse? Take a pair of binoculars, for instance. Maintaing the same magnification, a distant object will be diffuse and soft-looking, because the light has travelled through a lot of vapour and suspended particles. For this same reason, colours in the distance look much more faded than at close range, an effect most canvas arists are familiar with, and use this de-saturation to emphasize distance.

No wonder that all telezoom lenses loose sharpness at long ranges. This probably has got nothing to do with the focal distance, just the observer's range to the subject.

Just my two (euro) cents.

You bring up a very interesting point that probably has some degree of credence. However, it's pretty well documented that many lenses, particularly the low end lot, do have a sharpness problem at their respective zoom limits. What you are saying may only stand to exacerbate this problem.

[kirbinster]

The noise is the VR working. The active VR is for when you are in a car, train, plane, etc... a moving platform, otherwise you want active off. VR is for handholding, turn it off when you use a tripod. Please post some images so we can see if you problem is due to camera motion or something else. Include the exif data. Remember that at 300mm hand-held you really need to be shooting at something like 1/250th or faster, even with VR to eliminate camera motion as the cause of the lack of sharpness.