[ Beneath the Waves ]

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article by Ben Lincoln


It's easy to forget all of the accessories that are necessary (or at least very useful) for taking photographs.


A tripod is an absolute requirement for false colour multispectral photography today. I got two years of great service out of a bulky camcorder tripod that I bought for about $80 at a consumer electronics store. Its extra mass and reinforcement ensured a steady support for my camera. It eventually wore out, but it helped give me thousands of pictures over the course of its lifespan.

As its replacement, I bought a Bogen/Manfrotto "wilderness" leg system and a three-axis pan/tilt (camcorder-style) head to match. It is more sturdy, and its design allows its legs to spread much wider, meaning that very low-angle shots can be obtained from a well-supported position. I tried a couple of ball heads, but didn't like that design. This was the cheapest decent system I could find - well-heeled photographers have a lot of options in this area, especially if they're buying one type of tripod for the studio and another for the field. I was surprised to discover that the mounting system between legs and heads is standard across manufacturers, so if you find e.g. a set of Gitzo legs but prefer a Bogen/Manfrotto head, then they will (at least usually) fit together.

Sun Shades

Some means of shielding the camera from direct sunlight is extremely important for multispectral photography. Lens flare can easily overpower a near infrared or ultraviolet-A exposure, and providing shade will help minimize or eliminate hotspots. Traditional lens hoods are problematic because most of them must be removed first to switch filters.

I use a $15 umbrella from the drug store. I prefer "old-school" long umbrellas as opposed to collapsible designs, because in my experience they're more durable and therefore reliable. If you go this route, I recommend the "golf stick" design, in which the handle is not curved, but more like a sword handle. This is because I previously used one with a curved handle, and when it was attached to my frame pack (see below) would catch on tree branches and act like a naval aircraft arrestor hook.

Something to Carry Your Equipment In

Field photography can be a bit of an adventure. I don't want to have to worry about my equipment getting broken, so I use a hard-sided case. If you buy such a case at a photography store or electronics retailer, expect to pay through the nose. However, Harbor Freight sells an aluminum case for US$30 that even includes perforated foam so you can create a custom fit for your camera and lenses (or whatever else you want to store in it). These cases are great; they show up fairly frequently in television and film (along with their silver sister-product, although that one doesn't include the perforated foam) because they are functional, look "serious" and are cheap. For some reason, Harbor Freight only includes one half of the foam to "sandwich" the perforated section in, so the first step I always take with one is to cut another of the same size and place it below the perforated-foam layer, with the included "eggshell" piece placed in the lid as the top layer of the sandwich. It is still the best deal you'll find anywhere on a brand-new hard-sided case.

Within the case, I use a Tamrac filter wallet to hold my filters. Individual cases are too bulky. "Filter stackers" are great for infrequently-used filters of the same size, but it's a hassle to use them when you are changing filters between multispectral exposures. Some filters (e.g. the Baader U-Filter) don't even have front threads, so using them with a "stacker" case is right out.

An aluminum case full of ancient, heavy Nikkor lenses is fine for walking short distances, but quickly becomes a hassle on long hikes. In addition, it's generally a good idea to keep your hands free in such situations. For this type of activity I have a cheap frame backpack which has a main compartment big enough to slide the aluminum case into (with the long axis being oriented vertically). About 1/3 of the case sticks out of the top, but this helps provide protection against sneak attacks by cougars[1]. To keep it secure and out of the rain, I put the flap of the backpack over the exposed section of case, then run a bungie cord or two over that to keep it and the case firmly in place.

The frame pack also provides an easy place to attach the tripod and umbrella, and has a variety of small pockets for flashlights, rappelling gear, demolition charges, etc.

White-Balance Card

If there were one thing I wish I could go back in time and convince myself to do earlier, it would be to have bought a white-balance card in 2007 instead of waiting until 2009.

The idea of such a card (AKA "grey card") is simple - shoot a picture of the card under the same lighting conditions as your other photos from the same set, and it will allow your RAW-conversion software to perfectly[2] adjust the white balance and ensure ideal colour reproduction.

I'd read that description long ago, and dismissed it as audiophile-style nitpicking that didn't actually matter. What finally convinced me was reading Michael Reichmann's "Antarctica 2009: What Worked � What Didn't" article, which contains a glowing reference to the WhiBal card right at the beginning.

After trying one myself, I was immediately sold. With one click, the colour balance in a photo was exactly as I remembered them from when I was taking the picture. For $30, you really can't go wrong, and I suspect you will start kicking yourself as I did for not buying one earlier. The one exception would be photographers who don't shoot in RAW format. I can't imagine any of them have actually read this far, because the process I use must make their skin crawl, but using a grey card requires more effort if you are shooting JPEG-only.

The WhiBal also offer a flat response into the near infrared, so it can be used to help adjust the exposures in multispectral sets as well. Unfortunately, despite the manufacturer's claims, it does not provide a flat response into the ultraviolet, as discovered by Klaus D. Schmitt. For ultraviolet use, Klaus and Reed Curry both suggested different varieties of Teflon (PTFE) as an alternative, with Klaus having calibrated material custom-made, and Reed mentioning PTFE plumber's tape.

Cleaning Supplies

The last thing you want to do is be out in the field, get some dust or a thumbprint on your optics and not have a way to clean it off. Inside my camera case is a Giotto blower[3], a LensPen, a microfiber cloth, lens-cleaning solution, and a set of disposable lens tissues (to use with the solution for cleaning off the initial layer of very problematic fingerprints or dust/debris).

Sticky Bookmarks

3M (and possibly other companies) produce a handy "sticky bookmark"-type product which uses the same sort of safe adhesive as Post-It Notes®[7], and which have colour-coded tabs attached. These are extremely useful when using lenses that exhibit focus shift. For "studio" work (I use that term loosely), I will take test shots until I get the human-visible, near infrared and ultraviolet-A shots focused the way I want, then I stick one of these bookmarks on the focusing ring to indicate where to line it up for each of them. This also gives me a chance to get the exposure length just right. Once I have all three positions marked, I go back and do a final version of each band in quick succession. While this is not critical for subjects that are truly static (mechanical objects, et cetera), it is very helpful for things like plants which will subtly change position over the course of 5-10 minutes.

Here is a poor photo taken with my cellphone to illustrate:

Sticky Bookmarks
[ Sticky Bookmarks ]
Sticky Bookmarks



Gelatin Filter Holder

A popular accessory among UV photographers is a gelatin filter holder (such as Nikon's AF-1). This is not because they use gelatin filters, but because the filter holder can act as a convenient way of mounting a filter so that it can be quickly flipped down to allow focusing via the viewfinder (which is impossible with a UV- or IR-bandpass filter in front of the lens, since they block all of the light that we can see). I've also seen several people recommend them because they provide the easiest way to mount a Baader U-Filter (or other astronomical 48mm/2 inch filter) in reverse, which supposedly results in better performance. I have not tested this myself yet.

If you do buy an AF-1, be prepared to track down some obscure stepping rings to couple it to modern filters. Mine, at least, has 60mm filter threading on the front. Because this size is virtually unheard-of now, I had to get three rings to use it with my filters: a 60-62mm step-up ring (for larger filters), and a combination of 60-55mm and 55-48mm (or alternately 60-52mm and 52-48mm) step-down rings in order to attach a U-Filter.

Equipment - In Closing

This is not an exhaustive list. There are many other things that can be useful to bring along - a notebook to write down your lens/f-stop settings when using non-CPU lenses, extension rings/tubes for close-up focusing using non-macro lenses, etc.


Camera Tethering

One of the best uses that can be made of the USB port on a camera is to "tether" the camera to a PC, laptop, or tablet so that as each photo is taken, it is displayed on the much larger screen of the attached device. This is quite helpful when e.g. focusing macro shots, especially when the focusing needs to match between multiple spectral bands. Nikon has a basic tethering package available (for a price), and if you have a lot of money to throw around, it's hard to go wrong with Phase One's Capture One software. I am currently using DIY Photo Bits' Camera Control because:

It is definitely barebones, and definitely for technical users. On the other hand, it runs just fine on a laptop I got for free from the recycling pile at work, which is more than enough for hobby studio use. The few problems I've run into have been solved by either turning tethering off and then back on, or rebooting the laptop.

Lugging around a laptop when shooting outdoors isn't a whole lot of fun, so eventually I'm hoping to move to a tablet computer of some kind. The methods I've seen for tethering with an iPad are laughably complex - they involve carrying around a mobile WiFi access point, performing a multi-step process including FTP uploads, and so forth - so I am holding out for a Linux or Windows option.

For what it's worth, I actually gave Nikon's offering a try, and it crashed every time I tried to set up tethering. So if you are considering that package, I'd recommend testing it out with the demo version before making a purchase.


Of course, taking the pictures is only the first step in the process. An image-editing software package is required, and if you're interested in using the method I've developed for producing false colour images, you'll also need some way of aligning the exposures and compensating them for the slightly different effective focal lengths.

Image Editing

For image editing, obviously Photoshop® is the first name that comes to mind. Adobe's long-running product has a lot going for it: it supports 16-bit-per-channel images (which I highly recommend taking advantage of), it has built-in support for importing RAW files from nearly every brand of DSLR, it includes a huge variety of functionality, and it has a very well-thought-out UI. On the downside, it tends to be a little buggy, the uselessness of Adobe's support is legendary, and it is expensive. The basic product has a list price of US$700, the extended product has a list price of US$1000, and the prices for the Creative Suite packages only go up from there. These prices are perfectly fair for the professional market, but put the purchase of Photoshop® beyond the reach of the vast majority of non-professionals[4]. For this reason, although I think it's a fine product, I can't give it an unqualified endorsement.

The closest thing Photoshop® has to a contender today is the open-source GNU Image Manipulation Program, most frequently referred to by its success-limiting acronym of GIMP[5]. The GIMP is missing some important features (the most-relevant in this discussion being 16-bit-per-channel images), although supposedly the developers are working to add them, but it does have some built-in and add-on components that perform functions not available at all in Photoshop®. The GIMP also has a UI that many users find unintuitive. The specifics of this are hard to pin down - for me at least, it just feels "off", even though it's superficially very similar to Photoshop®[6]. This isn't a function of it just being slightly different - back in the mid-90s, I used Macromedia's competitor to Photoshop® (before Adobe bought Macromedia), and I was able to find my way around just fine. Still, it is very usable, and best of all it is absolutely free.

Alignment/Registration and Effective-Focal-Length Compensation

Most of the people who are interested in this kind of functionality are highly technical. Astronomers in particular will use image-registration software to combine a set of telescope photos of the same object (Mars, for instance) into a single image of higher resolution and clarity. As a result, all of the software to perform the work tends to be written by and for specialists in the field, and most of it is daunting at best when others try to make use of it.

Fortunately, there is a reasonably-friendly (although still complex) option: Hugin, which is a (free, open source) graphic front-end for the Panorama Tools set of command-line utilities (which is one of the "very difficult for regular photographers to use" packages I mentioned above). Hugin is most definitely a product of the Unix/Linux/Free Software mentality (if you haven't read Neal Stephenson's excellent - and free - "In the Beginning was the Command Line", you should - the part about the Hole Hawg if nothing else). That is, although it's intended to be used to stitch together a bunch of photos into a single panorama, it exposes a large amount of underlying functionality that would be hidden from the user in a commercial product. This is to the advantage of people like me, who want to use it for something similar but not identical; I could never use the panorama function built into some cameras or Photoshop® to achieve my goals.

There are two reasons that I make use of Hugin: first, although the sets of exposures I produce for a given false colour image are reasonably well-aligned due to the use of a tripod, that alignment is rarely 100% perfect. Using Hugin, I can get them lined up well enough that unless an object (or shadow, etc.) in the frame moved between shots, everything syncs up perfectly. The second is that due to my use of standard camera lenses, the effective focal length for an exposure varies between the human-visible, near infrared, and ultraviolet exposures. It's as if I were using (roughly) a 50mm lens for one, a 50.3mm lens for another, and so on. Hugin can also correct for this. Detailed instructions for the process I use are in the article Aligning Multiple Exposures in Hugin. The ideal result is that I end up with a set of images not so different than if I'd used an expensive lens designed specifically for multispectral work.

Why Registration and Effective-Focal-Length Compensation is Important
[ Comparison ]

Here's a comparison between two versions of the NIR-R-G false colour variation of a photo that I took in Bodie State Historic Park. On the left is the result of working directly with the original exposures. On the right is the result after the exposures were processed through Hugin to correct the registration and compensate for the different effective focal length of the near infrared shot.

1. Well, maybe.
2. Some lighting environments are beyond the range of compensation by some/all RAW-conversion software. Ultraviolet ("black") lighting, and some others can be mostly corrected, but don't be surprised if they're problematic. This is no reflection on the grey card - it's a software problem.
3. Don't try to cheap out and buy something like the squeeze bulbs designed to clean out babies' ears. Seriously, it won't work.
4. Adobe has a long history of selling (for a much lower cost) crippled versions of its flagship products. This practice to me is ridiculous; it would make sense if e.g. Photoshop® were a physical product, and the "LE" or "Elements" versions actually cost less to manufacture due to lower component count. However, because it's software, Adobe is actually spending more money to pay its developers to hobble their software, which then costs the same amount to manufacture as the full version. They do offer significant academic discounts, so I wonder why they don't just give that same discount to non-professionals. They're a member of the BSA, so if they think a professional studio is buying the lower-cost version (which they can do today if they have any students on staff), they have their own Software Gestapo to send around to the premises.
5. I am hardly in a position to criticize developers for giving their software whimsical names. However, the names I pick for mine are at least somewhat descriptive, and aren't abbreviated to words that (literally) mean "cripple" or remind people of the infamous scene in Pulp Fiction.
6. One specific complaint I have is the use of the GTK+ file I/O dialogues. I realize that the developers are trying to maintain internal consistency between The GIMP across platforms, but I feel that maintaining consistency with the host UI is more important. It's shades of the ugly old-school interfaces that cross-platform software written in Java had for years - it was consistent, but terrible. Similarly, I really think that in the Windows build, a so-called "multiple-document interface" should be used. It may not be how things work in Linux or OS X, but it is how applications of this type are supposed to be designed for Windows. I have three Linux systems; when I want to use Linux, I do. If I'm using Windows, I expect the software to follow the general conventions of that OS.
7. Actually, my understanding is that the reverse is actually true - the bookmark application was developed first in the lab, but it was Post-It Notes® which were the first commercial success.
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