Digital Panoramas - part two

Following on from my last post, let's have a look at two more techniques for digital panoramas, both involving using software to stitch together multiple images, for which I use ptgui.

4. Stitching - using a panoramic head

There are a few of these on the market, all of them allow for proper alignment of the shot images, by rotating the lens around it's nodal point. You have to calibrate for each lens you intend to use, but it only takes a few minutes to do.

I use the Nodal Ninja 5, which offers solid support but is correspondingly big and bulky, and you really need a levelling base on the tripod for ease of use. I generally put the camera into portrait (vertical) mode, and shoot 6 or 7 overlapping frames, depending on the lens.

This setup gives me around a 108 megapixel 3:1 image when using the 24 megapixel Nikon D3x, but I often have to crop this a little, as it's quite difficult to visualise the finished result. Still, plenty of resolution to play with.

There's a couple of options on the market for automated, motorised panoramic heads, onto which you mount the camera, programme in what you want in terms of angle-of-view, and let the electronics do the 'hard' work. Trouble is, I don't feel that the actual picture-taking is the hard work bit. Great idea I suppose if you need to repeatedly shoot the same angle of view, or need a 360 degree view for VR purposes. Gigapan sell a model suitable for use with SLRs. the Epic Pro, which is available in the UK from Red Door VR (they also sell Nodal Ninja products).

Eardisland

5. Stitching - using a shift lens

By mounting your camera rigidly on a tripod and taking a sequence of 3 images with a shift lens, 1 with no shift, 1 with maximum left shift and 1 with maximum right shift, you'll get either a 2:1 image when using full frame, of 3:1 if using DX format.

For my purposes, DX works best, and offers 32 megapixels when used with the Nikon D7000, enough for a print up to 30" wide at 300ppi. A 24 megapixel DX SLR would take this to nearer 40".

The advantages of this solution are that it is relatively portable, and also it's possible to use a tilt movement with Nikon's PC-E lenses, to give great front-to-back sharpness. Also, the images are nicely aligned with big overlaps so your stitching software has an easy job.

Unfortunately, tilt/shift lenses are quite expensive (although you could try the older Nikon AI shift lenses, but you need to watch compatibility as you can damage your camera depending on the model) and metering can be tricky. Also as with any stitching technique, it's difficult to pre-visualise the final result (although I find it a bit better in this regard than using a panoramic head).

(The above applies to the Nikon PC-E lenses, which offer +/-11mm of shift, but I believe Canon's equivalents are very similar)

Digital Panoramas - part one

I love the panoramic format, and when I say panoramic, I mean 3:1 aspect ratio, printed big (and by big I mean a minimum of 2 to 3 feet wide). In my opinion, anything wider than 3:1 looks contrived, and anything narrower isn't really a pano. Nope, 3:1 it has to be, and nothing works better in conveying a sweeping vista.

Let's look at the options in the digital world:

1. Film(!)

Yeah I know I said 'in the digital world', but you can't ignore the 6x17cm film format, as made popular by the likes of Colin Prior. There are a few camera options available, both new and secondhand, but the obvious choice are the Fujifilm G/GX 617's. Now out of production, but readily available second hand.

Obvious advantages are the fact it is a 'native' 3:1 format, so what-you-see-is-what-you-get, and quality is very high due to excellent lenses and that massive slab of film (it really is 5.6cm x 17cm, so does fulfil my 3:1 requirement!). Scanning at just 1200dpi would be good enough for a 27" wide print at 300ppi.

Downsides are that these cameras are expensive to buy and run: c£2000 body only and c£2 per shot for film and processing (not including scanning!). Depreciation should be pretty low though.

2. Dedicated digital panoramic camera

There's only one of these that I know of - the Seitz 6x17 Digital. First, the good news is we have native 3:1, plus a resolution of 160 megapixels! Yep, that's enough for a 70" wide print at 300ppi.

Bad news is this camera, with a couple of lenses, spare batteries and a very powerful computer is going to set you back close to £40,000! There's a 18 megapixel version which is cheaper but doesn't quite  make a 2-foot wide print at 300ppi, and as we'll see this resolution can be met by a digital SLR these days.

If you're still reading after that price tag, see what can be done with the 160 megapixel version by David Osborn of British Panoramics.

3. Cropping

Most digital SLRs have a sensor in the 3:2 aspect ratio, so by simply cropping away half the frame, we get 3:1. Good news is many SLR's have gridlines in the viewfinder, or we can use black tape on the LCD to mask the image, allowing us to visualise the final panoramic composition.

We have to be careful about exposure, as the camera is metering from the whole scene, but with care and bracketing this could work quite well. Given that a 24 or 36 megapixel DSLR will make a 20" or 24" print at 300ppi, this is quite an easy way to get into the format, but it doesn't really allow me to make the sort of print sizes I would like.

(A while ago I even asked Nikon if they could introduce a 3:1 viewfinder mask on the D3x, just as they have for DX and 5x4 formats, but I got the standard 'this is not something we're planning' email back. If they were to do this for the D800, I'd probably buy one, but they probably won't)

In part two, I'll be looking at stitching techniques.

Frozen Lake

Creating Panoramas

A couple of people have asked me about creating panoramas, which I've been doing a lot just recently, so I thought I would post about the three methods that I use.

1. Cropping - dead easy this one, simply take a single exposure as normal, and then crop it down to your desired format. Positives are that you can visualise how the final image will look, and your camera may even have guidelines in the viewfinder or on the LCD to help compose the picture. Also, this method works for moving subjects, can be used handheld and requires no additional equipment. Downside: you are throwing away perhaps half the resolution of your camera. Tip: to help with composition, stick a bit of semi-transparent gift tape across your LCD to show your preferred aspect ratio, but still allows you to compose using the full frame when you want to.
2. Stitching - the basic principle is to create a row or rows of overlapping images that can then be 'stitched' together on a computer. Quite tricky to do without a specialist panoramic tripod head, which helps to eliminate parallax error so that the images captured will stitch accurately in your software (I use PTGui). Positives are you can achieve very high resolution images: typically when I create a 3:1 panorama using this method, the final image will be 40 to 80 megapixels, and that makes a high quality panoramic tripod head very economic compared to the cost of a higher-resolution camera. Of course, this method doesn't work with moving subjects, and can be quite slow and cumbersome to set up. It's also more tricky to visualise what the final image will look like. Oh, and that super-duper wide angle lens you just bought? Sorry, but you are more likely to be using a short telephoto with this method :-)
3. Shift lens - both Canon and Nikon produce shift lenses that allow you to create 2:1 panos on full 35mm frame digital SLRs, and 3:1 on cropped-sensor cameras. You simply take 3 images, one shifted left, one with no shift, and one shifted right. These are then stitched in software as method 2. There is no problem with parallax as you are shifting the lens and not the camera, and it's slightly easier to visualise the results, especially using Liveview. However, shift lenses tend to be expensive and quite heavy.

For me, option 1 is really a stop-gap when an unexpected opportunity presents itself and there isn't time for the one of the other methods (or you don't have the right equipment with you!). My preference is for method 2, with 3 as an option when travelling light.

Weston-Super-Mare

The Grand Pier at Weston Super Mare, taken at dusk, aperture priority with minus one-stop compensation. A tricky exposure, given the huge dynamic range from the shadows on the left and under the pier, to the highlights of the illuminations. I wanted to keep some 'texture' in the sky and sea so I chose to let the Ferris wheel in the centre blow-out a little.

Shuttleworth Panoramic

Taken this afternoon, using a Nikon D300, Nikon 85mm PC-E lens and Nodal Ninja 5 panoramic tripod head. Original stitched image was 80 megapixels, but this crop brought it down to a mere 42......

Same Tree, Different Sunrise...

...and a different vantage point, technique and orientation.

This time I decided to get much closer to the tree and use a wide angle lens (a 30 year old, battered 20mm f/2.8 Ai-S). Unfortunately the lovely mottled pre-dawn sky cleared before the sun hit it, due to the strong wind, so I switched to 'Plan B'. On went the much younger 24mm tilt/shift lens, cue panoramic format using the shift function.

Lessons learned from recent morning trips: I ditched the wellies, favouring Fox Arctic boots instead... toasty toes means one less distraction from photos! Single gloves were replaced by a pair of thin grippy gloves (shame Lowepro have discontinued their 'Photographers Gloves'), with an oversized pair of Buffalo mitts over the top. I can forgive the giant comedy Kenny Everett hands for the warmth!

Overall, very pleased with the results from this shoot. Again though, may be should have gone for a lower view point to emphasis the tree. Wonder if my current enthusiasm for sunrises will continue as the temperature drops...

That Tree Again

I was looking for a better vantage point for a sunrise picture of this tree, when I noticed a large stone in the field, which just happened to mark the exact spot I was looking for.

This set me thinking about an entirely different picture: a vertical panoramic with the stone as foreground interest. I knew that I would need a telephoto lens to compress the perspective (i.e. bring the stone and tree apparently closer together). This would cause me another issue in that I would not have sufficient depth of field to render both the stone and the tree sharply. Also the foreground was in virtual darkness, so I would need to light it some how. Flash seemed the obvious answer, and I liked the idea of the surreal effect this might give.

In the end, my simple pre-visualisation had become a technically complex image to execute. I decided to use a focus-stacking technique, using two captures: one focused on the stone and lit by flash; the other focused on the tree and exposed to keep the intense colours in the sky. Add in the fact that all of this had to be executed by torch light and in the freezing cold! The two images were merged in Photoshop and then cropped to the 3:1 (or is that 1:3?) format you see.

Does it work? I must admit that I am not 100% convinced, but it is faithful to my original visualisation, and I think, quite striking. Let me know what you think.

You can buy a print of this image here.

Photographic Notes

This image was taken with a Nikon D3 and 70-200mm lens (set to 125mm) and a SB-800 flashgun attached by a SC-17 cord and held above the camera, which was set at knee height on a tripod.

If I were to try a similar shot, then I would consider using a 85mm tilt/shift lens on a DX sensor camera, which would possibly deliver the front to back depth of field needed in one single exposure (the stone and the tree are in focus in this image, the bits in front and between are not, but I do not think this detracts from this image too much).

Good Morning World

This mornings sunrise, taken with Nikon D3 & Nikkor 50mm f/1.2 AI-S.

Could have done with getting a bit closer or higher to give a bit more separation between the tree and the horizon, unfortunately neither was practical. Still, not a bad start to the day!

Been Busy ;-)

No update for quite a while, as I've been extremely busy. The main thing that's been occupying my time has been putting together a new system for stitching panorama's, which is something I really want to do more of. It's a great way to create very high resolution images in a distinctive and rewarding format, but it is not without it's challenges.

When I say 'system', it's really my personal methodology for visualising the results and then creating the individual images that make up the final image. Most of the gear I'm using is fairly standard, but there is one bit which I'm using which I've developed myself. I've not read or heard of anything similar elsewhere and so I'm keen to keep this to myself for now. Until that is, we've at least proved it out and clarified what is sensible to do in terms of protecting our intellectual property.

What I will do over the coming weeks is share some of the results, so look for some upcoming posts with example panoramas!

Yorkshire - Rainbow & Barn