Tip 7: Panoramic photography on the cheap!

I am in process of moving my blog to my AustralianLight Landscape Imagery web site. Please find an updated version of this article at http://www.australianlight.com.au/blog/post/a_beginners_guide_to_shooting_panoramic_images/

The Poor Man's Pano Head

Not being one to shell out the big bucks if I can make it myself... I set out to make a cheap panoramic head that would provide me with nodal point rotation.


First place was eBay looking for a macro focusing rail. I was lucky enough to find an AU seller with an Olympus rail that had been listed only moments before and it had a "Buy Now".... sweet! So 2 mins and $49 later it was mine. (I also noticed that the same seller had a set of extension tubes.... I figured "Heck, I have a macro focus rail... I might as well have some macro as well!! "Another 2 mins and $20 and they too were mine)

I was very pleased when the items arrived, as they were brand spanking new!!! I seriously doubted that these had even been close to a camera! The Olympus rail is extremely solid and well built and I couldn't have been happier with the purchase.

Ok... so I got the rail, next step was to mount the camera in vertical orientation. A quick stop at the local hardware and a $3 bracket (yet to be painted in the pix) was purchased. 2 small holes were drilled... one to mount the camera and the other to mount the bracket to the rail (in a position with the lens over the rail) and bingo!... a Panoramic head for less than AU$55!!!!


On this image I have marked the offset so that you can see how the camera rotates around the lens nodal point. This means that no matter where the camera points during it's rotation, the camera-subject relationship does not change.

Nor does the relationship between objects at different distances change.... so when stripping together everything matches and blends perfectly.

The macro rail is perfect for this application, as it allows fine offset adjustment so that the lens nodal can be found for different focal lengths.

Interesting side note: Thanks to the internal zoom, the nodal point for the 17-40 L does not change throughout it's zoom range. This makes compositional changes very easy once the head is set at the nodal.

I have plans for a second bracket that will hold a flash above the nodal. This flash will be used with my "tracing paper" diffuser (more on that in another blog later) in the vertical position and allow for smooth internal exposures without multiple shadows.

What’s this “nodal” thing again?

Your camera lens projects a reverse image…. while cleaning your lenses, you may have seen that the image through the lens is upside down and back-to-front.

No, you haven’t seen this? OK then, try it now…. Remove the lens from your SLR and look through it (sorry compact camera owners with fixed lenses, you don’t get to play this game) and you will see everything is flipped in both the vertical and horizontal directions.

So given that this is the case, we know that the light that enters the front of the lens on the right, exits the lens on the left….. and conversely, the light that enters on the left, exits on the right. From this we can rightly assume that at some “point” within the lens, the light “crossed”.

This point is the “nodal point” or effectively the “optical centre” of the lens (not the physical center… measuring the outside of the lens and dividing it in half is meaningless…. unless you want to know how long half your lens is).

So why is this important to us photographically?

Imagine yourself sitting on the outside row of a merry-go-round. (not the gold horsie… that one’s mine, you can have the silver one) Look out from your position to a friend who is standing still and watching (They are thinking… “How embarrassing is this!! A 43 year old goose riding a merry-go-round…. Sheesh!”)

Your friend has just won a stuffed animal and is hiding it behind their back (you are now thinking…. “How embarrassing is this!! A 43 year old goose winning stuffed animals…. Sheesh!”)

As the merry-go-round rotates, your position in relation to your friend changes…. As your position changes you get to sneak a look behind your friends back and see that it’s an elephant (….bugger! You wanted the giraffe!).

Now change positions on the merry-go-round and imagine that you are standing in the dead centre. As the merry-go-round rotates your position in relation to your friend does not change. At no time are you placed in a better position to see what your friend is hiding behind their back.

This is what is important to us as photographers…. We can rotate the camera taking multiple images and each image will overlap with the previous, because at no time will the camera see anything that is hiding behind some thing else, it will effectively take one big photo over multiple frames. (More important, is the fact that the disappointment of getting an elephant and not a giraffe is postponed for a little while longer) ;-)

Let's look again at the 2nd image above... Here you can see that the camera does NOT rotate around it's own base, instead it rotates around a point located within the lens and above tripod centre .... this is the lens nodal.

This diagram shows how nodal rotation does not effect the relationship between objects.

Nodal rotation allows for easy stitching of images because (and to put it quite simply), everything lines up no matter where you point the camera.











The following diagram shows how objects appear to move in relationship to each other, when a camera is rotated around a point other than the nodal. (eg the camera base mount)

This presents impossible challenges for stitching, as no two areas that you are trying to blend will be the same. This can be overcome ONLY with physical intervention on the image in post process and when you may have as many as 15 images to blend, do you really have the time?

Nodal rotation is much easier and no matter what you paid for your pano head, it will seem cheap in the long run with the time that you will save!!




At this point, I will take a moment to mention that hand-held panoramas are possible, but these are best kept for compositions with distant subjects only.


So how do we determine the nodal?

There are a number of databases available on-line that will let you know the offset required.... these are great for fixed focal lengths, but are of little use when you are using a zoom, because each time you position the zoom, can you really be sure of the exact focal length that you have selected??

From my experience with this, I have found that setting the nodal by eye is very effective and accurate. To do this, pick 2 objects at different distances (larger distances are better) and position them in the right of frame. Note the relationship between these objects (eg are they aligned, one just touches the other etc).

Now rotate the camera and position the same objects in the left of frame. Again note their relationship, has it changed?? If it has changed you have not rotated around the lens nodal. Adjust the offset distance and repeat the test.

After a little bit of tweaking you will find the nodal and see that left frame/right frame views of your objects do not change. Now you are ready to take some panos!

Tripod setup: Yes you MUST use a tripod if nodal rotation is required, as this relies TOTALLY on the fact that there is a fixed point of rotation. You cannot hand hold and rotate around a nodal, it is simply not possible.

Make sure that your tripod has a firm footing on the ground. Using a level (some tripods have levels built in) and the tripod's adjustable legs, make sure that the base plate of your tripod head is level in all directions.

Still using the level, make sure that your tripod's top plate (where the camera normally sits) is also level in all directions. Now carefully place your camera/pano head and secure it well.

Oh... I should mention, it is really nice to use a solid stable tripod. A camera, lens and pano head can be quite a load with the offsets involved and fiddly little tripods are not recommended.


Landscape or Portrait? Well you can shoot in both, but I feel that portrait orientation is best. Why? ...I am glad you asked. When you think about it, a panorama gives you the ultimate wide angle lens. In fact every lens in your kit becomes a wide angle that is capable of a full 360 degrees (you can keep going round and round if you wish), so why not maximise your vertical FOV (field of view) by turning your camera into the portrait position.

Image overlap: When taking images make sure that each image overlaps the last be at least 1/3 (1/2 is better) as this will give your panorama software (I use PTGui) plenty of room to find points of alignment and plenty of room for your blending software (I use SmartBlend within PTGui) to make smooth, invisible transitions.

Exposure: You will need to fix your exposure from the start, so that it remains constant for ALL shots. If you allow your exposure to vary you will not get smooth transitions across your panorama image. Here I recommend shooting in manual mode and setting the exposure to just maintain detail in the brightest part of the image.

Large rotations can provide great variation in exposure and I think it best to maintain highlight detail and pull detail out of the shadows later if required. (Remember, if you blow the hightlights there is nothing left to recover in post.... blown is blown!)

Focus: I have found that using a common focus for all images works well. Stopping down your lens for lots of DOF will keep both near and far objects acceptably sharp with this technique, but depending on the effect you are after, you can elect to have shallow DOF or selective focus just as you would in a normal single frame shot.

If your subject distance varies greatly with the rotation, you can even focus with each frame and allow the focus differences to blend from frame to frame. Experiment with this and see what works for you. Sometimes this technique is successful, sometimes not.... it depends on the variation in the subject distance.

Focal length: Panoramas can be made from any focal length provided that your lens does not provide uncorrectable curvilinear distortion. (eg super wide angle or fisheye lenses)

So pick your focal length to suit your subject. In this image I am only interested the distant view and the close foreground is not important. So I have used a longer focal length of 112mm (70mm on 20D). If I had used a wide angle lens the more distant objects would have been quite small....

View this image large: http://www.potd.com.au/gallery/albums/userpics/10002/ABigWideLand.jpg

In this image I wanted more foreground and sky, so a wider focal length was used...

View this image large: http://www.potd.com.au/gallery/albums/userpics/10002/HighOnAHill_Stitch.jpg

So that's the images... now how to stitch them?? Well there are a number of applications that are available to do this and I will let you find one that floats your boat, but I will recommend PTGui and the Smartblend plugin http://www.ptgui.com/ as I have found the results nothing but excellent!!

I should also mention that it is wise to overshoot your panorama by 2 or 3 frames each end. When being stitched the individual images are "warped" to fit together, the is means the final result tapers at each end.

This is not a problem if you don't mind cropping some off top and bottom, but when you are a megapixel monster like me, you want every bit of image data that can be salvaged. So over shooting moves the taper out to unwanted sections of the image, these can then be cropped off the end without effecting image height.

One last thought..... Don't be afraid to try different subjects. Many panoramas are of landscapes and the pano format is perfectly suited for this, but panos can also be fun even in tight situations....

It's up to your imagination where you think you could use the panorama view.

These and some of my other panoramas can be viewed at my gallery link below. When in the gallery, please search "pano".

Cheers

Rusty
AustralianLight - Landscape Photography


UPDATE: Panoramic photography on the cheap! - PART 2 is now online.


Tags: panorama panoramic pano landscape image photo photography wide format 16x9 617