G Dan Mitchell Photography

(Note: Originally posted in January, 2008.)

Earlier this week I posted an older photo from Racetrack Playa at Flickr and got a lot of comments and a few questions. In response, I said that I would post something here about this location – so here goes…

The Racetrack Playa is in Death Valley National Park in south-eastern California. The Playa is the site Death Valley NP’s famous moving rocks (a.k.a. “sliding rocks”) phenomenon. Rocks, some of which are television-sized, have left tracks behind them as they have traveled across the surface of the playa. (See a post from earlier today for one photograph – there are more in the Death Valley section of my Gallery.)

No one has actually seen the rocks move, but there has been a lot of speculation about the process by which the rocks manage to travel across the playa. I’m no expert on this, but here’s some of what I’ve heard. First of all, while you are free to have a different opinion, I’m not convinced that aliens did it. (Though it would be a heck of a good joke on us.;-)

One theory involved a combination of wind and water. While you might wonder how water could play a role in a dry place like Death Valley, it most certainly can. In fact a playa is a feature formed when water washes sediment down from surrounding hills into a lower basin. The water spreads onto the playa and drops its load of sediment. When the water dries it leaves behind an extraordinarily flat surface. The thought was that rocks sitting on a very slippery surface of the playa might be moved by strong winds. Observations tended to make this scenario unlikely. For example, it was calculated that the winds necessary to move the largest rocks would have to be several hundred miles per hour. It gets windy there, but not that windy.

A refinement of the theory adds ice to the mix. Imagine a thin layer of water on the playa with the slippery surface underneath. Now freeze a thin layer of ice on the top of the underlying water in this shallow “lake.” (And, yes, it very definitely gets cold enough there to freeze water.) Now the winds would not have to work directly on the rocks themselves, but could instead act on the whole frozen surface, much as they act on the arctic ice pack. As the ice moved, the rocks embedded in the ice would be dragged along. This seems to make sense given the observation that groups of rocks often follow parallel paths across the playa surface.

The rocks seem to come from a low rocky hill at the south end of the playa. While they can be found in many other areas of the playa, the greatest concentration is near this formation.

Access to the Racetrack Playa is typically by way of an awful 27 mile gravel road that starts near Ubehebe Crater. (I’m no expert on desert travel or on these roads, so consult the Park Service for current and more reliable information if you go.) The road has been badly washboarded every time I’ve been on it – some people are so distressed by the conditions on the road that they turn around after a few miles of driving. For most drivers this makes for very slow going and it can take up to about two hours to get out to the playa. I met one driver of a very large truck who was convinced that “once you get above 30 mph the road smooths out.” I don’t recommend that approach. Slow and careful is probably a lot safer, especially for those without extensive experience driving roads like these. I know that I sit back and take it slow.

The last time I checked the Park Service recommended a “high clearance vehicle” for this road, and I concur. I have seen some vehicles without such clearance and it seemed to be pretty rough going, not to mention that you increase the risk that the undercarriage will be damaged by rocks. (If it has rained or snowed, all bets are off. Best to stay away. You certainly aren’t going to walk on the playa when it is wet anyway, are you!?)

Soon after you pass Teakettle Junction you will catch your first view of the playa ahead and/or to the left. You still have a ways to drive before you arrive at the playa and drive along the right side. You’ll want to keep going if you plan to see the best rocks, though it is worth stopping at the Grandstand, a large rock formation in the playa not far from where it starts. I’ve had good luck photographing this feature during the late afternoon.

Continue on to pull-outs near the far end of the playa for closest access to the rocky hill and the largest number of moving rocks. You’ll need to leave your car and walk a good distance out onto the playa. (Don’t even think about walking on the playa unless it is completely dry. Foolish and inconsiderate visitors have done so, and their footprints mar the scene for years afterwards.) Before long you’ll start to see the rocks. One plan is to head for the low hill where the rocks originate and then explore outwards from there.

There is a small “camping area” a short distance beyond the end of the playa. It is very primitive, consisting of little more than a couple of wide spots in the road and one dilapidated outhouse. There is no water whatsoever. I have camped there and it is very quiet and peaceful. I’ve also see people sleep in their cars back at the turnouts right at the playa.

My ideal trip works something like this: Go during the cool season. Almost no one would want to try to visit this place in the summer. Most visit in late fall, winter, or very early spring. My visits have all been during the first week of April. Drive out to the playa in the afternoon, arriving a few hours before sunset. If you have time, stop to photograph the Grandstand in the afternoon light. Then head on down to the south end of the playa and figure out where you’ll sleep that night.

By the time the light starts to become interesting you’ll want to be out on the playa, perhaps with a few shots already scoped out. Shoot like crazy for the next few hours as the sun drops and finally sets, continuing on after sunset as long as the light is interesting. Head back to your car and grab some dinner. (The last time I visited I met some fellow photographers and we had a great time sharing food and drink.) If there is a full moon (or maybe even if there isn’t) head back out to do some night photography. This is a wonderful place to photograph star trails, and there are a ton of interesting opportunities on full moon nights once the moon finally makes it over the ridge located to the east. Finally, completely exhausted, head back to your camp for the night.

Rise early the next morning – well before sunrise. You want to already be out on the playa before the interesting light starts. The morning lighting is interesting and somewhat challenging. All I’ll say is that there are mountains to the east that block the first light, yet the very earliest light will illuminate some interesting subjects.

Soon, most of the playa is in full sun. I generally shoot a bit more, but by this time I’m running out of gas – and getting hungry for some real food. I head back to the car, say goodbye to the playa and start the long drive back to the paved road that begins near Ubehebe Crater. (Don’t pass up on photographic opportunities as you drive this road though.)

Finally, a few random thoughts – some in response to questions I’ve received.

• Someone asked how often the rocks move? I’m not sure but not often – the interval must be measured in years.
• Someone else asked how they keep visitors from “tracking it up” when it is wet? Good question, and an important one to mention. There are footprints on the playa left by inconsiderate visitors who wandered about when the playa was muddy. Their footprints remain for years. If you visit when the surface is wet please do not leave tracks on the playa, even if that means coming back a different time. Fortunately, the road is so long and so bad and there are no services out there – all of which drastically limit the number of visitors. I’ve seen perhaps as many as 20 people out there at once, but on one other visit there were only two of us.
• Another photographer asked about the effect of the eastern ridge on sunrise photography. I touched on that above, but there is indeed a very tall ridge to the east that keeps the area with the concentration of rocks in the shadows until later in the morning.
• And what about the ridge to the west at sunset? There is also a large ridge to the west of the main part of the playa, and the road past the playa runs along its lower east edge. This feature casts a shadow on the northern portion of the playa well before actual sunset. My advice it to photograph there a bit earlier – I’ve had good luck photographing “The Grandstand” in the late afternoon. The sun hits the southern portion of the playa later in the evening since the valley opens to the west from there.

G Dan Mitchell :: Jan.17.2008 :: Commentary, Locations, Popular :: 6 Comments »

Sellers sell, and many buyers buy, UV (ultraviolet) filters for their DSLR and other cameras. The advantages are said to be twofold: some reduction of haze that is invisible to the human eye but which the sensor purportedly might register, and some protection of the front element of your lens.

On the other hand many photographers wouldn’t think of putting an extra layer of unnecessary glass in front of their lenses. They would rather accept the (rather small) possibility of a scratch on the front element of a lens than possibly reduce the quality if their images and/or they prefer to protect the lens by using a lens cap and lens hood.

I’m in the latter camp. I don’t own any UV filters and I can think of darn few situations in which I’d want to use one. (One possible exception being the use of some of Canon’s sealed lenses on which the seal is completed by adding a front filter – and here only if I were to use the lens in an extremely hostile environment, and with a fully environmentally sealed camera body such as that of the Canon 1 series.) My preference is to handle my camera and equipment relatively carefully, keep the gear in bags when not actually using it, use a lens cap, and to almost always use a rigid lens hood. Continue Reading »

G Dan Mitchell :: Dec.27.2007 :: Commentary, Equipment, Popular :: 12 Comments »

I just read a forum thread on dealing with “sensor gunk” on DSLR cameras. I posted a response and thought I’d share it here as well:

When I got my first DSLR I was very upset if I got any dust in a shot. I was also very paranoid about cleaning the sensor*, having read two many posts about how you could damage the sensor. Now that I’ve used DSLRs for a few years I’ve gotten over it and life is much, much easier.

Here is a summary of my approach** to dealing with sensor junk…

Rule #1: I don’t worry too much about a small amount of dust. I rarely can get a sensor clean enough to get perfect, dust-free shots at smaller apertures, and when I do the dust will soon return. Rather than worry too much I’ve found that it is easy to quickly fix most small spots in post-processing. Using one or the other tool, I can usually deal with most dust spots in a matter of a few seconds in Photoshop.

Rule #2: When the dust gets to the point that dealing with it in post is no longer efficient, I try the easiest thing first. When I notice a larger than usual speck or when the build-up gets to the point that post-processing cleanup is either taking too long or not working right, I use a blower to try to clean out the worst of the stuff. More often than not this is enough and I can go back to relying on rule #1. Point the tip of a good blower bulb into the chamber but keep the tip itself just outside. As you blow a few dozen puffs into the chamber and toward the sensor change the angle of the bulb to ensure that you get full coverage. It is probably best to hold the camera with the open chamber facing down.

Rule #3: Sometimes rules #1 and #2 aren’t enough. At this point I try a static charged sensor brush, being _very_ careful to avoid letting the brush touch anything but the sensor itself. Yes, the brush can pick up other stuff in the chamber, and I have learned from experience to avoid this. However, most often the brush is all I need to use to get my sensor back to “sufficiently clean” status. With care and a bit of luck the brush method can sometimes get the sensor absolutely clean. The whole task takes me just a minute or two. I rarely have to escalate past the “blower and brush” technique – probably not more than once or twice a year – and in nearly all cases I can get the sensor glass very clean this way.

Rule #4: On rare occasions rule #3 fails, too. If the contamination is adhering too firmly to the sensor surface I resort to wet cleaning with Eclipse fluid and PecPads. I can rarely get it right in one attempt, so I plan on having to work at this a bit. Be very cautious to not use pressure or “scrub” the sensor glass. Let the fluid loosen and/or dissolve the material and gently wipe it off with the pad attached to the “spatula” tool. Read the instructions for this cleaning method very carefully before attempting it. It isn’t terribly difficult but there are a few ways you can go wrong including: pressing too hard and damaging the coating on the sensor glass, transferring lubricants to the sensor from other parts of the camera chamber, leaving streaks on the sensor. Eventually I get a reasonably clean sensor with no streaks.

Rule #5: On very rare occasions a combination of methods is required. Often the wet cleaning works well for me but leaves a few spots of dust on the sensor. For this reason I frequently follow the wet cleaning with a quick once-over with the static charged brush.

From all of this, it might sound like I’m sensor-obsessed. I’m not. Remember rule #1 is the one I follow most. I usually go months between real sensor cleaning sessions.

*I’ll anticipate that someone might feel obligated to write, “You aren’t really cleaning the SENSOR! You are cleaning the glass cover over the sensor, you nitwit!” Yes, I know that. It is just easier to refer to the whole assembly as “the sensor.” :-)

UPDATE: Since I originally wrote this I acquired a Canon EOS 5D2 body which includes an automatic dust reduction system that vibrates the sensor when the camera is turned on and off. I can report that this method seems to be very effective. I’ve had the camera for 9 or 10 months now, and I have yet to need to clean the sensor at all! I occasionally spot a small bit of dust or two when I shoot at small apertures, but the spots seem to disappear of their own accord  within a few shots.

UPDATE: In late 2008 I purchased a Canon 5D2, which has a dust-reduction system. It “vibrates” the sensor (as I understand it) when the camera is turned on or off, thereby dislodging dust from the sensor (AA glass) on a regular basis. I did not have high hopes for this system when I got the camera, based both on my understanding of how it works and on some initial published reports that were not encouraging. After using it for a year, my opinion has changed almost completely. I find that the “dust shaker” system on this camera is actually very effective. I have yet to need to do a manual sensor cleaning – although I used to do this more or less monthly with my older 5D. When a dust speck does show up occasionally, it usually disappears a few frames later after I switch the camera off/on.

**Disclaimer: This report describes what I do, but I am not any sort of certified expert on these things – as I wrote, this is “my approach.” I strongly urge you to seek out and learn from other official sources of information on sensor cleaning and related issues. The inside of your camera contains fragile and sensitive electronic and mechanical components and it is possible to cause damage while working there. You should read and carefully consider warnings from the manufacturer of your camera and any accessories and tools you use on it. If you are not convinced that you are competent to do this work on your camera, you can always take it to a professional. I do not claim that my methods are the best or most appropriate, nor that they meet the standards of the manufacturers of the camera equipment nor do I recommend that you use my methods in place of manufacturers’ official recommendations.

NOTE: If you join the site you can leave a comment or question on this post – and I’d love to hear from you. There is also a separate discussion forum connected with the site that supports more extensive threaded discussions.

G Dan Mitchell :: Oct.20.2007 :: Commentary, Equipment, Popular, Technique :: 4 Comments »

(Formerly titled “Summer 2007 Backpacking Photography Equipment” – most recent update on July 8, 2010.)

I do a fair amount of backpacking each summer, often spending at least three weeks on the trail in the Sierra Nevada. (This is in addition to other non-backpacking trips to the Sierra and elsewhere. It helps to be a “gainfully unemployed” college faculty member during the summer. :-) I’ve been a backpacker for over four decades, and I’ve evolved a backpacking photography setup that works well for me.

A few years ago I had worked out a pretty good back-country photography kit based on the Canon 350D/XTi. For many photographers there are real advantages in using one of the smaller cropped sensor bodies – less bulk, less weight, smaller lenses, and quite fine photographic quality. However, I switched to full frame and acquiring a full-frame 5D forced me to think more carefully about what I carry.

While I would like to have all of my gear with me, the load would be unmanageable. (At least at this stage of my life. When I was young, strong, and foolish in different ways than I am now, I would sometimes head out onto the trail with loads weighing up to 75 pounds.) Ironically, while I have lightened my load of backpacking equipment considerably during the past few years – moving more in the “ultra-light” direction – my photographic equipment load has increased. The bottom line is that I consider very carefully what I carry, considering the upsides and downsides of each piece of equipment and occasionally making compromises if I think a piece of gear can be left behind.

Here’s what I carry these days:

• Canon 5D Mark II (formerly a Canon 5D) – Heavier and bulkier than the cropped sensor body, but worth it for the higher resolution and the better small aperture performance.
• Canon 24-105mm f/4 IS L lens – This is a great standard lens for my purposes. I’m not necessarily a big telephoto shooter so 105mm is enough for most shots. The 24mm wide end is also wide enough for many situations. Having IS means that I can more successfully shoot handheld when necessary – as is often the case when I’m on the move. The f/4 aperture is fine, especially in combination with the IS. For this type of lens, the weight and size are not too bad at all. When I need to really keep the weight down I may take only this lens.
• Canon 17-40mm f/4 L lens – While the 24-105 stays on the camera most of the time, the 17-40 is my preferred lens for some types of landscape work, often done early or late in the day when I’m not carrying the backpack and can therefore more easily work slowly and with a tripod. Since I generally shoot this lens in the f/8-f/16 range it provides great sharpness and DOF. When I take two lenses – my most common set-up – this lens joins my 24-105.
• Canon EF 70-200mm f/4 L Lens – This is a wonderful and very useful lens. Not only does it provide almost twice the “reach” of the 24-105, but it is an admirable lens for close-up work where the longer focal length can provide narrower DOF and good bokeh. I hate to leave this lens at home on longer trips, and I often carry it on trips of a few days or base camp trips mostly devoted to photography. This lens gets its own padded Lowepro case and usually rides inside my main backpack.
• 77mm circular polarizing filter – This size fits the 17-40 and the 24-105mm lenses and will work on the 70-200 with a step-up ring.
• 77mm 9-stop neutral density filter -  This is a useful filter for certain types of images that require longer daytime exposures.
• Multiple 16GB or 8GB CF cards – I carry at more than I think I’ll actually need since cards are light (and relatively inexpensive these days) and I’d rather not run out of storage capacity. (As I write this, I’m considering moving to 32GB cards given the 21MP images of the 5D2 and the decreasing price of the cards.)
• Batteries – I take a lot of photographs sometimes, and I also like to do night photography. I don’t want to be caught short, so I typically carry at least three batteries and sometimes more, especially if I think I’ll be doing night photography and/or using Live View a lot on the 5D2. Despite the cost of additional batteries, for my purposes this is still a better bet than carrying fewer batteries and adding a solar charger.
• Velbon El Carmagne 540 carbon fiber tripod legs – While this setup is smaller than what I prefer to use in other situations, it provides a good combination of decent height, stability, light weight, and small packed size for backpacking. Because it has four leg sections it packs fairly small and easily stows on the outside or back of any of my packs. (By the way, this brand and model of tripod might seem like an odd choice for someone doing the sort of photography I do. I keep thinking I should get something more mainstream, but the darn thing really does work well, pack well, as is light.)
• Acratech Ultimate Ballhead – This tripod head weighs only about one pound and works very well – this is a great backpacking ballhead, and one that I use for my “regular” photography as well.
• Lowepro Toploader Zoom AW bag – I use this with a chest harness to hold the 5D plus the 24-105 (with hood), along with most of the other photo gear. The bag is sturdy and includes a rain-cover – though the whole thing can go into my main pack in case of truly bad weather. (The 17-40 could ride in the backpack in a smaller Lowepro lens case, but most often it fits crosswise into the bottom of the Topload bag.)
• Canon remote release
• Assorted accessories – Lens cleaning cloth, sensor brush, blower, Philips wrench, etc.

I never have had the courage to weigh the whole mess, but I think it is somewhere in the 12+ pound range. By the standards of my ultra-light backpacker friends (whose total base load may be 12-15 pounds!) this is an outrageous amount to carry. On the other hand, fellow photographers may be wondering how I managed to get by with only limited lenses and a small tripod! (In August 2008 I met a fellow at Moraine Lake in SEKI who was carrying two Nikon DSLR bodies and four lenses! Later that summer I met an experienced Yosemite back-country photographer equipped with three complete systems: full-frame DSLR, medium format digital, and large format film! Not surprisingly he had arrived with the assistance of a pack train…)

I do miss my full size Induro C313 tripod, but not nearly as much as I expected – and certainly not enough to carry the extra bulk and weight. In most cases the smaller Velbon will go high enough, though I do need to stoop a bit to see the viewfinder. It is sturdy enough and very flexible in terms of its adjustment options.

I usually do not miss my longer and heavier 100-400mm zoom. I may have missed a very small number of shots by leaving it at home, but I’m generally more interested in short telephoto to wide angle in the back-country. (As I mentioned above, I do occasionally take the 70-200mm f/4 on shorter trips when I’m willing to carry a bit of extra weight. I might take the 100-400 instead of the 70-200 if I were headed into an area where knew that the extra reach would be needed – for example, if certain wildlife opportunities were my goal – but I would begrudge the weight!)

The large Lowepro Topload bag with the chest harness is (pardon the awful pun) a mixed bag. It really is a fine product and the chest harness system is effective. You can even use it as a virtual shoulder strap by disconnecting a couple of the four strap attachment points. It is great to be able to fit virtually all of my photo equipment into one sturdy, weather-resistant, manageable and accessible bag. There are downsides, though – not the fault of Lowepro, but just the result of trying to accommodate all of the needs of the backpacking photographer with one bag. One unavoidable issue is the size of the bag, especially when carried on the chest. In rough country it is a disadvantage to be unable to see your feet! I have become adept at looking around the sides of the bag in many situations, though I have to be more careful of my footing in rough country. Trekking poles become even more useful. During extended cross country sections (such as class 2-3 routes) I sometimes feel more comfortable removing the bag and carrying it inside my main backpack. Having issued these disclaimers, I still rely on this bad and recommend it strongly.

I’ll add that while carrying the larger full-frame camera is worth the extra bother (and size and bulk) for me, many photographers will be very well served by a good crop sensor camera, particularly one of the smaller ones like the Canon “Digital Rebel” series or current versions of such cameras from other manufacturers. Frankly, unless you regularly make prints in the 20 x 30 range a good crop sensor camera is capable of producing excellent results, especially if you use a tripod, fine lenses, and careful technique. (If you don’t use a tripod and all the rest, the odds that you’ll get photographs that will stand up to such large print sizes diminish greatly.) Not only are these cameras potentially lighter and smaller, but equivalent lenses can also be smaller and lighter. There have been times when I wished for a digital version of one of the old high-end rangefinder cameras with a couple small lenses. (I still hope that we’ll eventually see a high quality, affordable APS-C sensor rangefinder camera with either a good zoom or a few good primes. Along these lines, some of the newer fourth-thirds system cameras could be a great option for many back-country photographers, though I have no personal experience with them yet.)

All of this having been said, am I contemplating any significant changes to my backpacking setup? In a word, no. For my purposes this system works very well.

(Questions, comments, observations? You are encouraged to leave a comment…)

G Dan Mitchell :: Aug.26.2007 :: Commentary, Equipment, Popular :: 22 Comments »

Last month I wrote about a set of tests (“Full Frame Lens Test“) that I conducted with my lenses and my Canon 5D body. My object was simply to better understand how the camera/lens combinations would behave so that I could make better decisions about appropriate lenses and apertures while making photographs.

One discovery was that, compared to using a crop sensor DSLR, I can shoot at smaller apertures with good lenses on the full frame body. I tended to avoid apertures smaller than about f/8 on the crop sensor camera, but there seems to be little liability in using f/11 or even f/16 on full frame.

To illustrate I put together the following composite image.

The example includes five versions of a small section from near the center of a photograph taken with the 5D using the EF 24-105mm L lens at a 50mm focal length. The camera was on a tripod, MLU and a remote release were used, and the AF was turned off. The images are 100% crops – in other words, actual pixel size is displayed. (You would virtually never view a print at this magnification. These are equivalent to tiny sections from a print that would be about 5 feet wide!) The images have been slightly sharpened in post-processing, but are otherwise unaltered.

I shot at apertures of f/4, f/5.6, f/8, f/11, and f/16. In terms of the sharpness of this portion of the image, I am quite certain that all five examples are plenty sharp for making prints. That said, there are some differences. To my eye:

• The f/4 and, to some extent, the f/5.6 versions are slightly but noticeably softer at this magnification.
• The f/8 and f/11 versions seem to me to have approximately equal sharpness. Some parts of the f/8 image seem slightly sharper, but other parts of the f/11 image seem sharper. In the end they are pretty darn equivalent, though I’d probably give the f/11 a very slight edge overall.
• The f/16 image may be slightly less sharp than the f/8 and f/11 versions, but the difference would likely not be noticeable in a print. In any case, f/16 appears sharper than either f/4 or f/5.6.

After doing this test I no longer hesitate to shoot at f/11 or f/16. Not only does this give me the possibility of getting greater depth of field when I need it, but it also means that I can compensate for corner softness on some lenses (e.g. the 17-40mm) by using a smaller aperture without fear of losing center sharpness.

(Addition: 4/23/07 – Other Canon L lenses seem to give similar results, including my 17-40mm f/4 L and my 70-200mm f/4 L.)

Added 2/23/08:

In response to a question in a photo forum I put together a sample image showing corner sharpness from the same original images used in the example above. (The earlier example shows 100% crops from near the center of the frame.)

(image temporarily unavailable)

Technical info: Shot using a Canon 5D with the Canon EF 24-105mm f/4 L IS lens at a 50mm focal length. In aperture priority mode, the aperture was changed manually between shots. Initial focus was with AF, which was then switched off before shooting the series. Camera was on a tripod and MLU and remote release were used. Shots were converted from RAW with ACR and no additional post-processing applied. Print made at this resolution would be approximately five feet wide. The crop is from the far lower left corner of the frame.

In addition to noting the softer image in the corner at f/4, also note that the image is a bit darker due to the expected increase in corner light fall-off (“vignetting”) at the largest aperture. Sharpest version in this series shot with a FF body seems to be at f/11 as in the center crop example above. But note that f/8, f/11, and f/16 are not very different in overall sharpness – and in the end any of these apertures would produce a very sharp print.

In response to another forum discussion, I have added another example, this time using the Canon EF 50mm f/1.4 lens and showing performance at f/5.6, f/8, f/11, and f/16. In other respects the test is the same as described already in this post. This image is seen to the right and below.

(image temporarily unavailable)