I have seen some photographers apply ultra wide lenses for documentary street photography. Taking photos by ultra wide lenses of people in the street creates deeply distorted results. Now there is a question that what purpose may a photographer follow to get such results and whether these kinds of results are accepted as documentary street photos or not?
This style of photography using an ultra wide angle lens clearly goes against the ethos of documentary photography since it
presents the subject in a unrealistic way.
forces you to get so close to people that you influence their posture or expression, thereby altering what you seek to observe.
It is however, a perfectly valid form of artistic impression. The wide angle gives a surreal look to images by dramatically enhancing the foreshortening effect.
I concur that this is not documentary photography at all. Documentary photography seeks to capture things as they happen and as they were seen and to capture the emotion of the event. This kind of a style is very surreal and honestly, (imho) the sample photos are rather poor even for use of a wide angle lens.
Using a wide angle lens like this is the equivalent of taking photos in a fun house mirror. There is no apparent rhyme or reason to the stylistic surrealism of the way the subjects are distorted. It doesn't really add anything to the story the photo tells (at least for me).
Generally I see wide angle lenses used more to capture crowds and large amount of action (wide angle can help with the feel of action in some cases) or where the subject itself is already surreal and the added surrealism benefits the feel of the imagery.
Although the photographer of the example images has categorized the samples you show as "documentary", they're certainly not straight documentary. They're probably not really even properly called portraits; they might be called caricatures.
But you ask what purpose a photographer might have in making photographs in this way, and that I think is straightforward: the photographer wants to make something that looks interesting and different, rather than yet another example of the same thing over again. We may argue about whether it's successful, but the purpose of this approach is clearly to make a photograph that looks different from the expected.
In fact, in this particular series, the distortion appears to have a specific artistic purpose; in addition to the "documentary" and "street" tags, these are labeled as "conceptual", and are part of a small series provocatively titled "An Enemy of the People". (To see all seven, start with this one and then click next.) It seems very likely that the literal strongly-distorted views of ordinary people on the street is an intentional statement related to that title.
So, while the purpose of a distorted-perspective street shot may simply be humor, or nothing more significant than a way to force a new perspective onto an old scene, it can certainly be used in other ways as part of a photographic vocabulary.
With a normal or tele lens, you can easily focus on a detail and compose a few elements into a shot. With a wide angle, and especially ultra wide-angle, the camera is going to capture everything, so the image will be chaotic and full of possibly distracting details. So the pohotographer is going to have to work to try to make some order out of that chaos, and is necessarily going to have to get closer to his subject, like any wide angle photography really, so that there is somewhere for the eye to focus and not just a mess of background with no real subject.
By getting closer to the subject the shot will have a more intimate feel. Not like the photographer is a distant observer, but more part of the action. As a result the photographer is more likely to be noticed and more likely to get a reaction from his subjects, whereas with longer lenses you can often catch people unaware.
So for documentary photography, using a wide angle is going to most likely capture images of people who are quite aware of the camera, but you will get closer and more intimate with the subject, and you will also capture more of the surrounding environment with the shot.
