What’s Your Preference?

jdepould · #11 (**permalink**) 12-10-2009, 02:26 PM

Quote:

Originally Posted by LoveDSLR

Then you will like the new version. As a bonus, the VR II is very effective. I think I'll keep mine since I can use my other 70-200 lenses.

I miss VR, I used to have the 70-300, but I needed 2.8, and the 70-200 was out of reach.

Buying the same focal length three times is really inefficient.

kirbinster · #12 (**permalink**) 12-10-2009, 04:52 PM

Would someone be kind enough to explain in simple terms what it means to loose focal length. How does 200mm turn into 128mm???

jdepould · #13 (**permalink**) 12-10-2009, 04:57 PM

From Thom Hogan, bythom.com:

"Meanwhile, it seems that the number one topic of discussion on the net at the moment is the new 70-200mm VR II. Lower vignetting. Sharper in the corners. Better VR. But it loses focal length as you focus closer. That last bit has a lot of folk howling (at the closest focus distance the new lens is apparently about 128mm in equivalent focal length). There are pluses and minuses to that last bit. The VR II is sharper close up than the VR I according to reports I trust. But it does mean that you have to move closer and change perspective to get the same "subject size" at the 200mm marking and closest focus distance. How much closer? Well, if I'm calculating correctly, no more than 2.5' in any condition (but again, perspective will change if you move).

Let's deal with one aspect of the howls of protest: that Nikon is marking the lens deceptively. No, they're not. The standards that all the camera makers use for marking lenses states that focal length is defined by the distance from the rear nodal point to the focal plane when focused at infinity. The standards also allow for a lot of rounding, which means you can claim a 190mm lens is "200mm." This is why we can pick up five lenses marked "200mm" and get five slightly different results, even at infinity.

Things get worse at closer distances. Optically, you have lots of decisions to make. It appears that one of the decisions the Nikon designers made was to try to improve close focusing performance. In doing that, they also shortened effective focal length by an amount large enough that a lot of people have noticed (much like the 18-200mm controversy a couple of years back--it does the same thing at close focus distances).

At issue is whether the design change between the original and new 70-200mm is significant in practice. I can't say for sure yet, as I haven't fully tested the new lens and won't for a bit yet (I've got too many other things that you've been asking for me to finish first). It strikes me, though, that the primary thing that is being compromised here is perspective. For very close subjects, you're simply going to have to move a bit closer with the new 70-200mm. That's going to give you better sharpness, brightness, and less vignetting, but it's also going to change your perspective. The unanswered question is whether this is enough to cause real issues for most shooters. My guess is no, but it's only a guess at the moment. Bottom line: the new 70-200mm is going to change some shooting habits somewhat (you're going to get closer to near subjects), but that doesn't make it the terrible update that some seem to think it is."

Basically, because of the way most still lenses are designed (varifocal), selecting a close focal point can move the elements around in such a way that the focal length changes.

OsmosisStudios · #14 (**permalink**) 12-10-2009, 06:47 PM

It's a factor inherent in all IF lenses: the 18-200 was notorious for it too, though not to this extent.

User em-dee-aitch has a GREAT animation that shows the effects of racking focus from far to close. See the thread at DPREVIEW: 70-200 VR2: Massively Improved Viewfinder Animation... [Page 1]: Nikon SLR Lens Talk Forum: Digital Photography Review

LoveDSLR · #15 (**permalink**) 12-10-2009, 10:09 PM

Quote:

Originally Posted by OsmosisStudios

It's a factor inherent in all IF lenses: the 18-200 was notorious for it too, though not to this extent.

True. Some interesting numbers from A Question for Bjorn re the 70-200 VRII "warning" thread.

Nikon
80-200 177mm
70-200 f/2.8 VRI 180mm
70-200 f/2.8 VRII 134mm

Canon
70-200 f/2.8 153mm
70-200 f/2.8 IS 161mm

Sigma & Tamon
70-200 f/2.8 175mm