AF-S Nikkor DX 18-300 3.5-6.3 owners----Please read this

<p>Hello. I've been absent from this forum for quite some time but my password still worked, so here I am.<br>

I recently bought second-hand a AF-S Nikkor DX 18-300 f3.5-6.3 G ED lens. I thought this lens was going to allow me to leave some of the other lenses at home. Well, today was the first chance I've really had to do so testing on sharpness and contrast versus the other lenses that I own, and I came across something that I hope is not something that Nikon is trying to pull over on us. <br>

As I zoomed the lens in, the image became larger as it should. Everything was fine <em>until </em>I started doing comparisons. I found out that the 300mm end of this particular lens is NOT 300 mm, but approximately 135mm. I've checked it against my other Nikon lenses and aftermarket lenses. My 55-200mm DX Nikkor lens gets much closer. When I rack the 18-300 all the way out, the barrell looks like it's moving as it should. It just isn't giving the magnification that it should.<br>

Can someone who owns this lens please compare theirs with another lens to see what the 300 end looks like?<br>

Thanks in advance!<br>

DG</p>

<p>You may have come across the so called "focus breathing" that is often discussed here. Keep in mind that the focal length of a lens is defined when the lens is focused to infinity. If you focus to something really close, the effective focal length could be considerably shorter.</p>

<p>In other words, redo your tests when focusing to something that is very far away.</p>

<p>Thank you sir. I hadn't thought of that. I will recheck again later to see, but I don't think I'll gain that "lost" 165mm.</p>

<p>DG</p>

<p>Several Nikkor lenses have so called 'focus breathing', it's not exclusive to the 18-300mm DX and even top line lenses like the Micro Nikkor 105mm VR will do this, it's not a lens fault nor is it anything to worry about- just keep in mind that if you use this lens to really close focus the length will shorten considerably. </p>

<p>Anyone who wants to replicate this with their copy of the 18-300mm DX lens will need to know exactly the distance to the subject.</p>

<p>Take your camera outside and focus on something on the distant horizon and you will get obtain max. reach.</p>

The otherwise excellent 18-140 VR zoom is more

like 18-105mm at its closest focus as well.

 

As long as you're aware of this peculiarity it's not

too much of a problem. However, I do think that lens designers need to work a bit harder to deliver zoom lenses that do what they claim on the barrel.

 

It's not impossible, because Tamron's SP 70-300 VC zoom keeps its 300mm focal length pretty well across the focus range.

<p>While I don't have any 18-300mm DX zoom, here is a quick comparison between the 28-300mm AF-S VR and the 300mm/f4 PF AF-S VR. Both are FX lenses and I used an FX body. The 28-300mm zoom was set to 300mm.</p>

<p>While it is still not entirely the same as the 300mm/f4 focusing to some houses down the street, the difference is small at longer distances.</p><div></div>

<p>Both 18-300 and the 28-300 have identical maximum reproduction ratios (0.32x) reported on the Nikon USA website, at nearly identical minimum focus distances (around 1 1/2 ft) - so it is to be expected that they behave quite similar with regard to "focus breathing" when focusing close.</p>

<p>The 300 PF seems to have a bit more focus breathing than the old non-VR version as evidenced by a slightly worse maximum reproduction ratio despite a slightly closer minimum focus distance.</p>

<p>Compared to the above three zooms, the reproduction ratios of the two primes (0.24x and 0.28x) are slightly worse, but at almost three times the minimum focus distance. Assuming that focus breathing scales linearly with focus distance and taking the reproduction ratio differences into account, a "focal length reduction" by a factor of about 2.25 is to be expected (300/2.25 is about 135, as is indeed observed).</p>

<p>In essence, no one who purchases a lens should be surprised by "focus breathing" issues - the info to determine whether its present and to what extent is right in the specs. Most lenses show it to some extent - but only the most pronounced cases usually "get found out".</p>

<p>All lens designs involve a lot of compromises, especially when you have a super zoom that goes from 18mm all the way to 300mm (or even 28-300mm). If you want no focus breathing, you need to move all elements together when you focus, and that will introduce a very bulky design with slow auto focus since you need to move so many elements, not that AF on these 18-300mm and 28-300mm super zooms are all that quick to begin with.</p>

<p>i think you have to adjust your expectations accordingly with superzooms. and focus breathing is something you may encounter with a lot of lenses; it blows that my 70-200 II does it at a range where i dont want it to. but since that's not something i can fix, i just work around it. </p>

<p>Thank you to everyone who replied to this question. I did another test today and found out that at the long end of my 18-300 lens, the magnification is approximately what it should be. I am assuming that to be the case, as I was not able to get a good, measurable image far enough away to use infinity focus, but close to it. I'm sure if I had, the magnification would have been equal to my other 300mm zoom lens (Sigma 70-300). I have to admit I was skeptical of the lens, especially due to the fact that at a close focus there was such a huge loss of magnification. Now that I know about the "lens breathing" issue, i will forever remember to consider this when choosing which lens to use for a certain shot. Again, thank you for the great information and to Shun Cheung for going the extra mile with a photo comparision/illustration.<br>

DG </p>