Do lenses "go out of alignment" easily? and how will that affect image quality?

<p>It's just a question I want to ask. Please share your educated opinions. Thanks.</p>

<p>I assume you are referring to collimation of the optical elements. As a general rule lens only systems are pretty resistant to falling out of collimation. On the other hand, catadioptric systems (lens and mirror, e.g. reflex lenses) can be very prone to being uncollimated - it depends on the specific design.</p>

<p>If you are wondering about it with one of your lenses, take a defocused photo of a light source that is small enough and/or distant enough to serve as a point source (for camera lenses the easiest thing might be a light source behind some flatly drawn aluminum foil with a needle prick aperture at night, like a pinhole camera in reverse). You should defocus to the point where you get a series of concentric rings form the light source- the extent to which they depart from a circular pattern indicates the degree to which the optical system is out of collimation.</p>

<p>As to image quality, the result of severe miscollimation would be softness and an inability to achieve sharp focus, and sometimes an elongation (teardrop like) of point or near point objects. In practice, I'd be really surprised if this is ever noticeable with normal camera lenses (holding reflex lenses aside).</p>

<p>not unless you drop them. Consumer grade plastic zooms will not last as long as prograde lenses.</p>

<p>Leica lenses from 1950 to 1980 were the best. Mostly brass and aluminum mounts with real chrome plating. It would take a pro decades to wear one, in fact I have never seen a worn one.</p>

<p>I have seen lot of Nikkor SLR lenses from 1960 to 1980 that are pretty sloppy. Then again with the cost differential, you can afford a new one.</p>

<p>Any missallignment will deteriorate the image. </p>

<p>Other than the above mentioned mirror lenses, most lenses have no means of adjusting alignment to begin with. The elements can be rotated in relation to one another, but I doubt much of this is done. Basically everything is manufactured such that it meets tolerances as assembled. It's hard to wear out the focusing threads in metal designs; they feel sloppy when the damping grease gets forced out over time, but the parts were probably about that sloppy to begin with (unless you got sand in it or something). Plastic lenses may not be as rugged, but metal or plastic, don't drop 'em and don't worry excessively.</p>

<p>I have taken apart some manual primes and for those it is extremely hard to get any of the element out of alignment, unless there is some serious damage to the the barrel thats holding them, in which case you probably won't be able to use the lens anyway.</p>

<p> </p>

<p>I think bumping a consumer grade zoom lens featuring a long "multi-cam" extending barrel (even very lightly) could potentially lead to "serious consequences".<br>

Looks like the best way to invest in lenses is to get either the cheap and dispensible ones or the expensive pro ones that can take a beating.</p>

<p>No, they don't get out of alignment easy until someone try to clean it before they put it up on ebay :-)</p>

<p>That is how your new lens delivered:<br>

<a href="http://www.youtube.com/watch?v=9Z_i2L-dqN8">http://www.youtube.com/watch?v=9Z_i2L-dqN8</a><br>

This is how your repaired lens from Nikon repair center delivered:<br>

<a href="

<p>Those are some wonderful videos... So bad I'm sure not everyone know about that...</p>

<p>This is a good question since I tend to buy used lenses (mostly from KEH), I'd like to know if there is a quick and reliable way to tell if a lenses has been knocked out of alignment. I do tend to buy less expensive lenses new if I can afford them just because you assume that used lenses may have been dropped a couple of times.<br>

This also gets back to your earlier question about differences between the 55-200 VR and the 70-300 VR. It's just my opinion, but I think the 70-300 would stand up to a couple of drops better than the 55-200 even though both are consumer grade lenses.</p>

<p>Glen, the simplest answer to that question is to avoid buying any lens that's advertised as having a filter ring dent. If a lens has been impacted hard enough to dent the filter ring, it's been whapped hard enough to knock optical elements out of alignment. Repairing a filter ring dent won't fix the alignment problem.</p>

<p>Lenses with polycarbonate or non-metallic barrels present interesting challenges. They can be impacted hard enough to knock optical elements out of alignment without showing any external damage.</p>

<p>When buying used or demo equipment, ask specific questions and either get a return/exchange warranty or be sure the price is low enough that you won't mind absorbing the loss if the lens turns out to be defective.</p>

<p>In every case of a lens I've owned that suffered from alignment problems due to impact, the lens was still usable and capable of delivering good photos in all but the most critical situations. I might not be able to use them for architectural or landscape studies, but they were perfectly fine for candid casual photos.</p>

<p>I have a Nikon AF 18-70 lens which is notorious for the front element rattling aorund like a babies toy rattle. Like most people I was shocked and alarmed at first but found that it made no difference that I could see to the end results - which are as sharp as all get out. Surprising given the tolerances I assumed to be required.</p>