Nodal Slide Question

RogersDA

Looking at getting a nodal slide for my gear (in addition to some other stuff).

RSS has two slides, the MPR CL and the MPR CL II. RSS states that the first is for prime lenses with a nodal point roughly <110 mm to the sensor's plane. The CL II is for zoom lenses; e.g., the 17-40, 24-70, etc.

Question --> For lenses such as the 17-40, 24-70, etc. where the lens barrel does not expand doesn't the nodal point of the lens stay at one location? If so, why can't the MPR CL nodal slide be used for these lenses?

catspaw

I'm sure RSS will give you an excellent explanation if you call them directly.

FYI the Kirk one is excellent and a bit cheaper but still outstanding. I use it for macro work, even if some of the self prophetized 'purists' in the forms do not.

ziggy53

RogersDA wrote:

... Question --> For lenses such as the 17-40, 24-70, etc. where the lens barrel does not expand doesn't the nodal point of the lens stay at one location? If so, why can't the MPR CL nodal slide be used for these lenses?

Unfortunately, even though the external dimension of such a lens may not change the internal geometry of the lens probably does change. The lens' nodal point is often close to the aperture/diaphragm of the lens and, especially in constant aperture lenses, the apparent aperture does change position relative to the front of the lens.

I would expect you to need to adjust the nodal slide accordingly.

Andy

Ziggy is spot on.

T. Bombadil

RogersDA wrote:

RSS has two slides, the MPR CL and the MPR CL II. RSS states that the first is for prime lenses with a nodal point roughly <110 mm to the sensor's plane. . . .

Question --> For lenses such as the 17-40, 24-70, etc. where the lens barrel does not expand doesn't the nodal point of the lens stay at one location? If so, why can't the MPR CL nodal slide be used for these lenses?

does "RSS" mean "Really Right Stuff"?

i have their "ultimate pro omni pivot package" (they sell nice stuff). what Ziggy and Andy have said makes sense to me (and, in any case, i wouldn't doubt them). i will only add that in my experience, the nodal point of the nikon 28-70 does not seem to move (well, i couldn't see that it had) at different focal lengths.

i know your lens is newer, and could well be different. i only mention it because it surprised me when i didn't see the nodal point change.

i would suggest getting the MPR CL II because it is longer (and has a bubble level, which might be a benefit sometime). i'm sitting here trying to remember the distance from the film plane that i used last summer - and i think it was more than 110mm (somebody will probably point out that would have been wrong), but the extra inch and a half is worth the slight extra weight imho.

really right stuff package deals can save you some money.

RogersDA

ziggy53 wrote:

Unfortunately, even though the external dimension of such a lens may not change the internal geometry of the lens probably does change. The lens' nodal point is often close to the aperture/diaphragm of the lens and, especially in constant aperture lenses, the apparent aperture does change position relative to the front of the lens.

I would expect you to need to adjust the nodal slide accordingly.

That is kind of what I was thinking, though I really was not sure.

Andy wrote:

Ziggy is spot on.

As always...

Slide was ordered. So now I need to go out and practice with it so I have it more or less understood by the time I get to Bar Harbour.

RogersDA

T. Bombadil wrote:

does "RSS" mean "Really Right Stuff"?

Yup.

i have their "ultimate pro omni pivot package" (they sell nice stuff). what Ziggy and Andy have said makes sense to me (and, in any case, i wouldn't doubt them). i will only add that in my experience, the nodal point of the nikon 28-70 does not seem to move (well, i couldn't see that it had) at different focal lengths.

i know your lens is newer, and could well be different. i only mention it because it surprised me when i didn't see the nodal point change.

i would suggest getting the MPR CL II because it is longer (and has a bubble level, which might be a benefit sometime). i'm sitting here trying to remember the distance from the film plane that i used last summer - and i think it was more than 110mm (somebody will probably point out that would have been wrong), but the extra inch and a half is worth the slight extra weight imho.

really right stuff package deals can save you some money.[/quote]I ordered the CLII. So hopefully I will get out this weekend (if it arrives by then) and practice some.

T. Bombadil

RogersDA wrote:

So now I need to go out and practice with it so I have it more or less understood by the time I get to Bar Harbour.

are you going to DGrin Shootout '09? (wish i could) or independent vacation?

Acadia is a beautiful place. you will have fun.

RogersDA

T. Bombadil wrote:

are you going to DGrin Shootout '09? (wish i could) or independent vacation?

Acadia is a beautiful place. you will have fun.

Shootout 09

I watched Marc Muench work his magic at Shenandoah a few years back. I hope to be better prepared before I go this time.