Architectural photography is a skill that many might take for granted. After all, buildings are big, they don't move, and you simply take your pictures. What could be simpler?

Actually, in addition to extraordinary technical competence, photographing buildings well requires huge reserves of patience, immense reservoirs of passion for the subject and bottomless supplies of empathy.

This unusual combination is much in evidence in two exceptional, but very different, exhibitions on view in Washington: "Contemporary Urban Architecture in Helsinki: Photographs by Jussi Tiainen," at the Embassy of Finland, and "Tobacco: Architectural Photographs by Maxwell MacKenzie," at the American Institute of Architects.

In this demanding trade patience is a must because, even in an age of digital manipulation, natural light is the essence of the matter. Sunlight must strike the wall of bricks at just the right angle and intensity, shadows must fall just so across the courtyard and the sky, be it blue or gray or cloudy, must contribute to the overall feeling of the image. The difference between an adequate image and a great one can be measured in hours or even days spent waiting for everything to come together.

Passion lays the foundation for this waiting game. The best architectural photographers love buildings in whole and in part -- the way structures stand in the country or city, the materials and craft with which they were put together, the stories they tell about people and societies.

And empathy is the underpinning of the entire enterprise. The photographer must comprehend technically and intuitively why and how the architect made his or her choices, and then translate this understanding into an image that is at once an accurate representation and . . . something else. Really good architectural photographs often stand on their own as works of art.

It would be hard to imagine a greater congruence between the contents of an exhibition and the place where it is being displayed than in Tiainen's show at the Finnish Embassy. The crisply poetic building on Massachusetts Avenue NW, designed by Mikko Heikkinen and Markku Komonen and erected nearly nine years ago, remains one of Washington's best modern buildings and, more to the point, is a fine example of the fresh new wave of Finnish architecture.

Tiainen is the chronicler par excellence of this outburst of creativity. The catalogue of this world-traveling exhibition is the second book he's published on new Finnish architecture. A third is in the offing. Tiainen brings to the task an extraordinary sensitivity to the lightness, tactility and reflectivity of the steel structures and glass walls and roofs that many Finnish architects favor in their new buildings.

The images by and large are unpeopled -- Tiainen often conceives his photographs as abstract compositions of lines and shapes and colors. He'll give you a striking overall image of the building -- Heikkinen & Komonen's new Vuotalo Cultural Center in the eastern suburb of Vuosaari, for example -- and then zero in on specifics such as a mesh-metal wall, a curving interior stairwell or a parade of steel supports for colorful banners.

Each image is compelling on its own, and the combined effect tells you a lot about the totality of the building and the intricate harmony of part and whole. Tiainen's intense perceptivity is a lesson in itself -- through his eyes, we can sharpen our own responses to architecture's complexity and beauty.

An occasional side effect of this approach, however, is that the viewer can be left without any secure notion of how a building stands in relation to nature, other buildings and public spaces. Tiainen here counteracts such a lack of context with images of older Helsinki landmarks and splendid panoramic views of parts of the city.

Organizers of the exhibition in the Helsinki government further broadened the scope of the show by putting together an excellent PowerPoint video on four recent, large-scale, mixed-use, transit-oriented urban developments at the city's edges. It says a lot for these ambitious city-planning efforts that quite a few of the buildings in Tiainen's photographs are linchpins of these new communities-in-the-making.

With MacKenzie's photographs at the AIA, we change continents and moods. For this well-known Washington photographer, searching out the old tobacco barns was a definitive labor of love, supported by grants rather than a private client. Over three years, MacKenzie traveled the back roads of eight states on the lookout for subjects, photographing them in color and in black and white from many angles -- including aerial shots from a self-piloted, ultra-light aircraft.

For more than a decade, MacKenzie has nurtured a deep-seated empathy with the simple functional structures of America's rural past. The photographs of tobacco barns, many still in use, are not quite as elegiac as those in three previous AIA shows, which dwelt hauntingly on the theme of abandonment. Nonetheless, time's passing is a central fact in these photographs -- we see the effects on the weathered surfaces of these barns and cannot escape the feeling that their days are numbered, too.

Barns for the aging and curing of tobacco are about as simple as buildings can get -- post-and-beam wood-frame structures sheathed with wood planks left unsealed for ventilation and covered over, most often, with patched roofs of standing-seam metal. Situated usually on the edges of fields, near tree lines or roads, they stand lightly and sympathetically in the landscape.

MacKenzie has a special gift for intensifying this quality, particularly in the long black-and-white images that dominate the exhibition. It is in these horizontal views, with their powerful shadows and patches of light, that we feel most strongly the powerful kinship between building and place. The sharp lines of the barns and even their occasional irregularities, such as sagging walls or roofs, seem indelibly to reflect the lay of the land.

Contemporary Urban Architecture in Helsinki: Photographs by Jussi Tiainen, at the Embassy of Finland, 3301 Massachusetts Ave. NW, daily 11 a.m.-4 p.m., admission free, through Feb. 23.

Tobacco: Architectural Photographs by Maxwell MacKenzie, at the American Institute of Architects, 1799 New York Ave. NW, Monday-Friday 8:30 a.m.-5 p.m., admission free, through May 2.

A tobacco barn at the intersection of light and shadow, one of many such images captured by Maxwell MacKenzie during a three-year odyssey through eight states and now on display at the American Institute of Architects.Jussi Tiainen's sweeping and sensitive view of the new Vuotalo Cultural Center in a Helsinki suburb, part of his exhibit at the Finnish Embassy.