Comparing focal lenght of 18-200/3.5-5.6 VR and 80-200/2.8D

[benjaminm]

Hi,

 

I've compared these two lenses and I've noticed that the object size on image

made with the 18-200mm is much smaller as with my older 80-200/2.8D Nikkor (at

the same focal length on both lenses), especially when the object is closer

(<10m) to the the camera (D200). If the object is far away (from 20m to

infinity), then the size of object on the image is close to the 80-200/2.8D

zoom, but still a bit smaller.

 

I've also compared the 18-200 zoom and my older 24-50/3.5-4.5D at closer

distances. There was no difference in object size on the image (at 24, 35, 50mm

focal length on both lenses).

 

Is this normal?

 

Thanks,

B.

[rainer_t]

Benjamin -- "Is this normal?"

 

Yes, focal length is measured when the lens is set to infinity.

The real focal length of a lens at nearer settings is different and depending on its optical construction.

 

Rainer

[Michael R Freeman]

The 18~200mm is an internal focus lens, which changes focal length (shortens) as you focus closer. The effect will be most pronounced at the longest focal length. The 80~200/2.8D (assuming it is *not* the AF-S version) is not an internal focus lens, so if you focus both to a close distance, what you see is perfectly normal.

[andyjonesphotography]

Michael

 

The 80-200mm f/2.8D ED (non AF-S) is an internal focus lens.

 

Andy

[ShunCheung]

Sorry Andy. The first 3 versions of the 80-200mm/f2.8 AF are all optically identical. They are not really IF as far as their optical design goes, although Nikon designates them as IF. Only the 4th version which is AF-S is true IF.

[Michael R Freeman]

The 80~200/2.8D is FREQUENTLY mis-identified as IF, by sellers who should know better. It focuses via the front group.

 

Note the *official* model designation here: http://nikonimaging.com/global/products/lens/af/zoom/zoom80-200mmf_28d/index.htm

 

AF Zoom-Nikkor 80-200mm f/2.8D ED (2.5x). ED only, not IF-ED.

[Michael R Freeman]

Shun - Even Nikon does not designate the 80~200/2.8D as IF. However, I frequently see it incorrectly listed by retailers as IF-ED.<div></div>

[andyjonesphotography]

Shun

 

I stand corrected.

[ShunCheung]

I have saved all sorts of Nikon brochures and catalogs dated back to the 1980's. At least in one catalog (from the 1990's) I checked this morning, it does specify the 80-200mm/f2.8 AF-D as IF. They have since corrected that error in the more recent ones. Therefore, Nikon themselves are partly at fault for the confusion.

[andyjonesphotography]

Michael

 

Apologies, I got my info from a dealers website (www.vistek.ca)

 

Andy

[Michael R Freeman]

Not your fault Andy, and no need to apologize . :-)

 

Vistek is one of those that should "know better", considering they are a "high end" specialty photo dealer, but most likely they are simply repeating early product info errors from Nikon (as per Shun), and have never updated their listing for this lens.

[mjt]

howdy all ...

 

if it's any consolation, the 70-200 2.8G IF-ED VR is internal focusing ... if that's an important requirement for you, as it is for me :)

[ShunCheung]

Back in 1989, I bought the very first version of the 80-200mm/f2.8 AF, pre-D. I still have that box and it correctly does not specify that lens as IF. When you focus, the front element of it extends and rotates.

 

In the subsequent D version, Nikon kept the optical design but changed the barrel so that the new barrel covers up the movement of the front element, and you attach any front filter to the barrel instead of the front element. The advantage was that any polarizer wouldn't rotate along with the front element as you focus. As a result, the lens appears to be IF but actually optically it is the same as the earlier non-D version. I think that was when the confusion started. Of course, some of the errors in Nikon's official catalog in the 1990's contributes to the confusion.