How-To find the Entrance Pupil

[mikemalling]

Greatings my fellow Landscapers!

I few days ago I bought the NodalNinja 3 (NN3) for my Canon 10D cam, I felt it was time to move into new unknown territory to expand my photography skills – PANORAMA PHOTOGRAPHY.

I started studying the subject app. 6 month which lead to the acquisition of the NN3, approximately 2 weeks into the study I came across two new words in my photography vocabulary; “Entrance Pupil point” and “Nodial Point”. I quickly found out that, what makes a successful panorama photo is to know where the “Entrance Pupil point” is on the lenses you want to use for panorama photography.

Fine I thought, Google here I come! I was convinced it would not take me long to find this info for my lenses, I even thought this would be something the lens manufactures would post, I mean, they must know since they build the lenses, Boy was I wrong.

To cut a long story short, I still do not know where in terms of mm. from the lens base, the Entrance Pupil is on my lenses, why is this relativity easy information so hard to find even on the web!

Sigma 24-70mm F2.8
Sigma 12-24mm F4.5-5.6
Sigma 105mm F2.8
Canon 50mm F1.4
Canon 70-200mm F4.0 L

By posting this, I hope some of you might have the answers to 1 or more of my lenses and I eventually can complete the list, I will be happy to post them at other panorama sites so other can take advantage of this, and be spared the Hide and Seek I’ve gone thru.

Thanks in advance.

Brgds, Mike (Denmark)

[Tim Gray]

Here's a link.

I believe that entrance pupil is the correct terminology - although this fellow refers to the nodal point - it's the right technique.

http://www.path.unimelb.edu.au/~bernardk/t...hoto/nodal.html

[walter.sk]

To cut a long story short, I still do not know where in terms of mm. from the lens base, the Entrance Pupil is on my lenses, why is this relativity easy information so hard to find even on the web!

Brgds, Mike (Denmark)
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You will have lots of fun doing panoramas.  I have been doing them for the past 10 years, though, and have never been confronted with the need to know the location of the Entrance Pupil of my lenses.  The nodal point is important to avoid parallax errors, and is very easy to find.  But in all of the reading I have done about panos I have never come across a mention of the Entrance Pupil.

You sound like a person who does intense research in order to do something perfectly.  But with todays software, such as CS3's PhotoMerge, you can even handhold the camera and still get perfectly stitched panos.  I do understand the need for a perfectly level camera rotating about the nodal point if doing QTVR work, though.  

My advice to you is to keep researching, but go out and shoot right now.  I think your anxiety about doing it perfectly will dispel as soon as you see the results of your shooting.

I now do panos as a challenge to myself, where the camera is not level, and the distance between the foreground and subject vary greatly.  For example, standing on the shore of a river doing a pano of a bridge going across the river: the camera must be tilted up to a great degree, the depth of field must be great, and the lighting conditions vary widely in the scene.  

But in most landscapes, if you use a tripod and either a pano head or simply a focusing rail to set the rotation about the nodal point and make sure the long axis of the lens is centered over the center of the tripod, you will have instant success.  Relax, shoot, and most of all, have fun with it.

[fike]

Walter.SK is right about the precision needed for most large and wide panoramics.  The important exception is when you want to include foreground in the image.  I like to include foreground to provide the viewer some sense of scale.  I also like to shoot some panoramics where the furthest point in the image is less than 50' away, while the closest is 5' away.  In this case, a tripod and well calibrated head is essential.  

I have created my own calibration method that I think works well.  I work in a large room or outdoors.  I use a hyperfocal chart to estimate the closest I can get to the camera while still getting infinity focus where I set a vertical rod (like a long ruler on edge) in the ground.  Then, I take another long ruler and attach it between two trees or otherwise mount it horizontally, with the scale facing the vertical ruler. When I look through the viewfinder, the horizontal and the vertical rulers should intersect.   I position the camera so that I can place the vertical ruler on the far right side and the far left side by only rotating the panning clamp.  

Now, the trial and error starts.  Initially, you can move the camera fore and aft in the nodal slide to estimate the position visually through the viewfinder, but eventually, as you get more precise, you need to take a photo of the intersection of the two rulers at the far right side of the frame and then at the far left side of the frame for each tril fore/aft setting.  By using the LCD on the camera, you can zoom into the images and read the scale on the horizontal ruler to eventually make the number read the same on both far right and far left images.

I know it sounds kind of convoluted, but it works better than just lining up two vertical lines occuring naturally in the world, like so many of the other descritptions suggest.  I can never find good candidates.

[Panopeeper]

I described some points, which are additional to the usual descriptions, in

this thread

My advice is not to take any advice w/o understanding the background.

I have only the Canon 50mm f/1.4 from your lenses. Measured from the 20D, 40D socket screw vorwards, the entrance pupil is 49mm @ infinity, 50mm @ 4m. If you have some other camera, I can measure for you the distance betwen the socket screw and the lens mounting.

[mikemalling]

Here's a link.

I believe that entrance pupil is the correct terminology - although this fellow refers to the nodal point - it's the right technique.

http://www.path.unimelb.edu.au/~bernardk/t...hoto/nodal.html
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Thanks for the link Tim, I've already gone over this is my search for the "Holly Grail" on the subject - good reading.

Brgds, Mike

[mikemalling]

You will have lots of fun doing panoramas.  I have been doing them for the past 10 years, though, and have never been confronted with the need to know the location of the Entrance Pupil of my lenses.  The nodal point is important to avoid parallax errors, and is very easy to find.  But in all of the reading I have done about panos I have never come across a mention of the Entrance Pupil.

You sound like a person who does intense research in order to do something perfectly.  But with todays software, such as CS3's PhotoMerge, you can even handhold the camera and still get perfectly stitched panos.  I do understand the need for a perfectly level camera rotating about the nodal point if doing QTVR work, though. 

My advice to you is to keep researching, but go out and shoot right now.  I think your anxiety about doing it perfectly will dispel as soon as you see the results of your shooting.

I now do panos as a challenge to myself, where the camera is not level, and the distance between the foreground and subject vary greatly.  For example, standing on the shore of a river doing a pano of a bridge going across the river: the camera must be tilted up to a great degree, the depth of field must be great, and the lighting conditions vary widely in the scene. 

But in most landscapes, if you use a tripod and either a pano head or simply a focusing rail to set the rotation about the nodal point and make sure the long axis of the lens is centered over the center of the tripod, you will have instant success.  Relax, shoot, and most of all, have fun with it.
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Walter

Thanks for your reply. Sounds like you have me all figured out as you are correct in my search for knowledge to make it perfect.
However, the search is simply to understand, I have no problem in just grabbing my gear and get out there. As with many other things, one thing is theory another thing is practice. To put it simple, I just want to know what this is about, makes it a lot easier to correct if I know what’s broken so to speak.

My real interest is not panorama photos as such, I enjoy them a lot and admire those who make them, I’m much more interested in creating a large not giga pixel photo of a subject like landscapes etc.

My “mummy” camera in the digital world only olds 6.3Mpixel so I thought if I use a NN3 pano head, long lens and divide my scenery into smaller squares I could make a “mosaique” photo with lost of details at no extra cost….more or less.

Brgds, Mike

[mikemalling]

Walter.SK is right about the precision needed for most large and wide panoramics.  The important exception is when you want to include foreground in the image.  I like to include foreground to provide the viewer some sense of scale.  I also like to shoot some panoramics where the furthest point in the image is less than 50' away, while the closest is 5' away.  In this case, a tripod and well calibrated head is essential. 

I have created my own calibration method that I think works well.  I work in a large room or outdoors.  I use a hyperfocal chart to estimate the closest I can get to the camera while still getting infinity focus where I set a vertical rod (like a long ruler on edge) in the ground.  Then, I take another long ruler and attach it between two trees or otherwise mount it horizontally, with the scale facing the vertical ruler. When I look through the viewfinder, the horizontal and the vertical rulers should intersect.   I position the camera so that I can place the vertical ruler on the far right side and the far left side by only rotating the panning clamp. 

Now, the trial and error starts.  Initially, you can move the camera fore and aft in the nodal slide to estimate the position visually through the viewfinder, but eventually, as you get more precise, you need to take a photo of the intersection of the two rulers at the far right side of the frame and then at the far left side of the frame for each tril fore/aft setting.  By using the LCD on the camera, you can zoom into the images and read the scale on the horizontal ruler to eventually make the number read the same on both far right and far left images.

I know it sounds kind of convoluted, but it works better than just lining up two vertical lines occuring naturally in the world, like so many of the other descritptions suggest.  I can never find good candidates.
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Hi Fike.

Thanks for your reply. I'll keep your tricks in mind.

Brgds, Mike

[elf]

You'll probably find the entrance pupil is going to move around a lot in modern zoom lens.  It's also going to change when the focus point changes.  Even primes change focal length when changing focus points. My Olympus 35mm macro's entrance pupil moves from 70mm to 55mm when moving the focus point from 1:1 to 1:4.  It may be a bit more work to find and record the entrance pupil for all possible focal lengths and focus points.  

As a general rule, if your foreground object is more than 20' away you can shoot handheld with minimal parallax errors.  

Here's a little macro pano: http://img.photobucket.com/albums/v649/etfrench/10789_p.jpg