My new 400/6.8

<p>I've got one of these lenses for an upcoming nature trip. It hasn't been used yet, but it promises to be a unique experience w/ its' sliding focus and length. But I do have two questions.</p>

<p>(1) On the top of the viewfinder, when this lens is attached, there is a dark band, almost like a deep shadow, extending down the viewfinder, no more then 3-4% at most. Is that normal? The lens glass looks pristine, other then dust.</p>

<p>(2) What is the rotating locking device near the base near where the lens attaches to the camera? Is that where an extension tube goes?</p>

<p>W/o the shoulder stock, which I have no intention of using, this lens is very light, somewhere I would guess around 1200g or so. It's lighter then the 350/4.8, which itself only comes in at around 1800g, but because of the 400/6.8 long length probably at least a monopod will be required.</p>

<p>Any help on the above questions, or any other tidbits regarding the use of this lens would be much appreciated.</p>

<p>Many SLR's have mirrors that aren't long enough to intercept all the light rays from the lens. This allows the flange-film distance to be shorter, since a longer mirror would require the lens mount to be further out (when the mirror is up). When you use a long lens, or stop down a lot, you start to "focus" this loss of light, and it shows up as a dark band at the top of the image. Exakta and Topcon cameras are particularly subject to this.</p>

 

<p>I should of mentioned that I also have a 350/4.8 in the house too. Don't ask why I have two lenses of similar focal length. It's Leica, and one needs to pack it bags soon. But I don't see the same shadowy band with the 350.</p>

<p>Stephen,<br>

Regarding your second question about the rotating locking device near the base of the tube that attaches to the camera: it's the 90 degree rotation collar for shooting horizontally or vertically.</p>

<p>With the camera attached to the lens, depress the chrome latch near the top of the mounting tube and turn the camera from vertical to horizontal (or vice versa). It locks into place for both positions. The advantage is that with the camera + lens mounted to either the shoulder stock or on a tripod, you only have to use the rotation collar to move the camera from horizontal to vertical shots. The rotation collar engages in three positions: one horizontal and two vertical depending on whether you want your shutter button up or down for a vertical.</p>

<p>You'll love your 400/6.8. I've had mine since 1969!</p>

<p>Dan</p>

<p>It's a great lens, but I find I use it less and less (& wide angles more and more).</p>