Using a long lens I was able to put the elephant seal in the same picture as the scientists, while keeping their relative sizes. This helps to show the immensity of these creatures compared to people
Wide angle lenses exaggerate the distance between between two objects, while long lenses and telephoto lenses can actually compress the appearance of the physical distances between objects. Notice the size of the elephant seals head, relative to the size of the scientists. The pinnipeds head is much larger, even though you can tell that there is some distance between them.
If I had used a shorter lens for this photograph the relative sizes of the people and the elephant seal would have changed, unless I was far enough away that none of the subjects would have taken up much space in the picture. All of the detail would have been lost, and it would have become more of a landscape image, with scientists and elephant seals in it.
I originally learned this lesson from the movie Stand by Me during the train scene- where the boys are running along the trestle, trying to make it to the other side before the train can catch them. Listening to the directors commentary, they explained how they wanted to film the boys running from the train, without actually putting them so close to the train that they would be in danger if they tripped and fell. They explained how they used a very long lens (I believe it was 500mm or more) to visually compress the distance, keeping the relative size of the train, without forcing the boys to be running with the train on their heels, even though it appears so. In this way they were able to get realism and didn’t have to resort to a blue screen (this was before digital effects).
While I have never tried to film people running from a train, the lesson has stuck in my mind, because it can help show different objects without overly skewing their relative sizes. It can be used to frame someone or something silhouetted within the moon (making them move away from you until they are the same relative size as the moon, or a little smaller than it). Or by showing someone relative to something that they may not be safe being directly next to- trains, elephants, elephant seals, lions, etc.
When using a long lens to compress distance, there is one important thing to consider- aperture (which determine how in focus objects at different distances are). When the aperture is opened wider (i.e. f4 or f5.6) you will only have a small stretch that is in focus. Stop down the aperture, and the deeper your focus will become (i.e. f8-f22). That is more will be in focus at one time.
For this particular photo the aperture was f8.0, which is still fairly wide. This is why the people are somewhat blurred, while the bull elephant seal is fairly well focused. I would have liked to have the aperture closed down even more, but the light was very low, and my shutter speed couldn’t have dropped lower without having movement blur. My ISO was also as higher than I was comfortable with (1600), and I couldn’t have changed the aperture more than I already had without having too dark of an exposure.
Happy shooting,
Galen
Galen Leeds Photography 
I am glad you posted this link in your current post. Very helpful information and info I did not know. It also answered my question as to how far away you must have been in relation to these animals.