Nodal Point for Pano's & Macro Rail

[Ventureoverland]

OK, first off I hope this is in the right section. Mods feel free to move if it isn't!


I like to photograph two main areas, macro and landscape/panorama's.
I dont have a macro rail and on many occasions have thought I could use one. Likewise, many of my pano's often have a lot of parallax errors meaning lost parts of the image and increased difficulty stitching.


Im about to order a new tripod ball head form the USA and thought I may look at ordering a pano rail at the same time. This got me thinking...


Can I use a macro rail as a pano rail to sit the lens / camera over the nodal point? On the face of it, I cant see why not. The macro rails seem more expensive than a pano rail but I suspect thats because of the screw mechanism for the small adjustments needed for macro, but essentially (I think) they both move the camera forwards and backwards over the rotation /centre point of the tripod.

If the above logic isnt flawed anywhere I can buy 1 bit of kit and use it for two purposes... sweet!

I have yet to do a multi-level pano and I know thats a whole different ball-game!

Any thoughts?


Thanks
Jon

[arthurking83]

I don't have a macro rail as such .. but just use a sliding rail instead. Not ideal for focus stacking for macro, but the principle is the same.

I use this for may panos where I guesstimate the nodal point of the lens I'm using at the time.
Finding the nodal point is easier than I thought it'd be, so there's no reason you couldn't use a macro rail in the same manner.

But if you do want to get into multi level panos, then a proper pano head is probably advisable.

[Ventureoverland]

I don't have a macro rail as such .. but just use a sliding rail instead. Not ideal for focus stacking for macro, but the principle is the same.

I use this for may panos where I guesstimate the nodal point of the lens I'm using at the time.
Finding the nodal point is easier than I thought it'd be, so there's no reason you couldn't use a macro rail in the same manner.

But if you do want to get into multi level panos, then a proper pano head is probably advisable.

Thanks Arthur.
I cant justify a multi-level pano head thingy at this point in time as it wouldnt get used that often, plus I like the long wide look.

Unless anyone else can confirm the logic is flawed somewhere along the line, I think I'll got for the macro rail rather than the pano rail, if nothing else it gives me the micro adjustment for the macro side of things. Quick, course adjustment is also available with the arca-swiss style clamps.


Thanks
Jon

[Ventureoverland]

Further to my post above and after reading more theory about the nodal point I took the camera & tripod outside today and tried (without a pano rail) to establish just where the nodal point is on my 24-70 and 5D Mkiii.

It was very clear than when the camera is simply sat on the tripod that its not there! I then removed the camera from the tripod and hand held it so that the lens barrel was over the rotation point and swung the camera around through my 'test line of sight'.

I kept moving the camera "back" away from the tripod rotation point and kept the lens barrel over this point until the far object didnt move relative the near object...

I was quite shocked to see that the nodal point seems to be about 50 - 60mm from the centre of the 5D Mkii out into the lens.

Now, my camera and near object (a small tree) where about 5m apart and the far object (big tree) was about 25m beyond that. The point of all this rambling is that when you expand these scales and amounts of distortion out to a landscape, there is no wonder things look a bit odd and are thus difficult to convincingly stitch.

Once I found the approximate nodal point for 24mm, I then tried the same thing at 70mm - Guess what, the nodal point changes!!

Looking forward to getting my new gear and doing the same thing again, but a bit more accurately - Hopefully I'll be able to mark the rail somehow so I can set & forget going forward.

R
Jon

[arthurking83]

Hopefully THIS (http://wiki.panotools.org/Entrance_Pupil_Database) will make light work of any other lenses you have in your possession.

It's a link to a database of already measured nodal point suggestions, in the form of measured entrance pupil values.
Unfortunately ( I had a quick look for 'ya) but the Canon 24-70 doesn't seem to have been measured yet, or the database hasn't been updated .... so you may have to do the work yourself.

Nodal point always changes as it's dependent on both the focal length, but also on the lens design! That is very few same focal length lenses will have the same entrance pupil distance. Even lenses of similar focal lengths from the same manufacturer have entrance pupil values wildly different to their stablemates(eg. look at the database for Nikon 50mm lenses!!).
Once had an argument with someone that lens design is not as simple as the eye leads you to believe .. but of course that fell on deaf ears.
The design of the lens will dictate how it performs in the real world, so measurements have to be made to to ensure repeatability. Don't assume that what works for one lens is going to work for another.


As for sliding rail: Because I do very few panos myself but do like to have that same opportunity .. plus the macro things ..... I just got myself a 10" sliding rail from Hejnar. But with the sliding rail, I also got myself a short double clamp attachment($80ish). This double clamp attachment is two clamps screwed together, on on top and one underneath, and can be set to be parallel or perpendicular and I set mine to perpendicular. What this does is to allow you to slide the camera on the longitudinal plane along the sliding rail. So in effect this gives me the ability to slide the camera over a (nearly) 20" length along the top of the ballhead(but you need to stabilise the tripod if you're at the extreme ends of the tripod.

This is a slightly more expensive setup to the traidional fixed panorama or sliding rail with fixed bracket at one end .. but heaps more flexible, especially with setting up for macro shots.

If my description doesn't make sense, I can post an image later if you like.

[Ventureoverland]

Thanks Arthur,
The wiki page is most helpful.

I can pretty much visualise your setup. The RRS macro-rail I am looking at has the dovetail top and bottom, thus allowing the bottom rail slide to move along the tripod head clamp and the camera body on the slide to the top of the rail. This (I think) acheives the same result as you describe, i.e almost twice the movement of the rail length but it will not allow me to use a lens foot as I cant rotate one of the clamps 90 degrees - Not too much of a problem for me as I only have a lens foot for my 70-200 and I woundnt use that for this application.

Thx
Jon

[arthurking83]

Before you commit to RRS for clamps and rails, I strongly advise to have a peek at Hejnar's site (http://www.hejnarphotostore.com/index.php?main_page=index&cPath=1_29) for the same stuff. As good if not better in some ways.

I got RRS, and I got Hejnar, and in some ways his clamps feel a wee bit better. (he uses the same material, and is flexible to cater to any individual need you may have too.

I have many of his rails and clamps, but for the pano stuff I use a simple setup from his catalogue:

set of two 1.5"(American remember!) clamps which of course can be set to right angles.
10" rail @ 1/2" thick. The 1/2" thickness of the rail allows the clamp screws to pass each other without interference(if required) .. whereas the 3/8" thick rails may not.

These two items will cost about $120ish(plus postage). Most if not all of his rails have the safety screws at each end so as to stop a rail sliding completely off the clamp, which can be removable if required.
But, for added info, the 1.5" twin clamp set doesn't have the indentation to use this feature! In saying that tho and in two years of use, I've never had the camera or clamp slide off the tripod in any way, and these clamps inspire a natural tendency of operation that doesn't require this feature anyhow.
it's just nice to know with general use of the normal clamps with the safety feature that you're pretty much safe, if somewhat lacking in concentration :p

With that setup, you could screw the mini clamps to the rail itself if that's your preference for operation, as the system is modular.
Having tried both variations, my preference for all round use was for the rightangled mini twin clamp setup over the rail.

he also has a variation of the traditional L-bracket which is both very handy, and sometimes annoying to use(depending on usage need).
if you're doing panoramas, I strongly advise to use an L bracket too(if you don't already have one). His is a two piece design, that is still very sturdy.
The annoyance of the design comes in the form of difficult access to any side door on the camera(which I rarely use). But if the L-bracket becomes annoying at any point, which they can be sometimes for general handheld use, you can remove the sidebracket(hex screw) and just leave the base bracket if you still need occasional tripod use.


I've been thinking of getting a macro rail myself too(but at the moment I'm happy using the bellows for macros anyhow) .. but have no idea on the quality of Hejnar's macro rails!

And on the topic of macro rails, a gentleman on another forum had posted a small comparison of macro/focusing rails (being a very capable and somewhat very dedicated macro shooter), and he did note that the RRS focusing rails aren't as good as could be hoped for.
From memory, he posted that the Novoflex Castel-L and old Minolta rail and the old Olympus rails were the better quality units to seek out. Olympus rails are very hard to find, and the Minolta rails occasionally come up on ebay .. and the Novoflex rails are horrendously expensive!
(and note that Novoflex's versions of Arca Awiss compatible gear is not always fully compatible).

Because of his comments on the RRS rail, I'm a bit hesitant to try one of Hejnar's rails too, as they are based on a similar design.


Hope this helps.

[Ventureoverland]

Thanks. I'll have a good look.

Sent using Forum Runner

[dulvariprestige]

Jon I bought this rail from ebay, seems well made, the only problem was when I started using cokin X-pro filters, they would hit the rail, I ended up cutting it down, but I will order a 6" rail, this could also be a problem with 100mm filters too.
This rail with an L plate has been working really well, I've even managed to do a couple of double row panos that came out pretty good.
http://www.ebay.com.au/itm/8-Rail-with-clamp-Nodal-slide-4-Kirk-Markins-rrs-wimberley-acratech-foba-/330753193377?pt=US_Lens_Adapters_Mounts_Tubes&hash=item4d026d35a1

[arthurking83]

Jayde, see (one of)my reply above about using a double sided mini clamp for these sorts of rails.... instead of the fixed clamp version.
Saves having to hack otherwise perfectly good gear!

I think if you purchase directly from Hejnar, they end up very slightly cheaper.

[Sar NOP]

Another easy way to do a pano is by stitching 3 photos taken with a tilt & shift lens : tilt left, tilt 0 and tilt right.