Subject is One Mile Away...

[mtd885]

I'd like to take some on the water shots of the sinking of an artificial reef off of Key West this month. The Coast Guard will be enforcing a 1 mile perimeter on boaters in the area. Not wanting to break the law I'd like to know if it's possible to get some good shots from the perimeter line using my Canon 50D body with a rental lens since I do not have a telephoto greater than 135mm. What lens will I need to do the job? Can I get by with a 400 mm with an 1.4 extender which I can rent or borrow? The ship is over 500 feet long. Any and all advice is more than welcome and thanks for taking the time to respond...best Michael

[Doug Pardee]

Let's do the math.

The length of the ship is approximately 1/10th of its distance away—over 500 ft vs. 5280 ft per statute mile. Yeah, yeah, it's probably a nautical mile, but the point is the ship's about 1/10th of its distance away.

So, using a lens with a focal length of "x" mm will result in an image on your sensor that is 1/10th of "x" mm. A 400mm lens will result in 40mm-long ship image. The sensor on a 50D is 22.3x14.9mm. So at 400mm, the sensor will capture about half the length of the ship. At 200mm you'd capture just about a full ship-length (if shot from directly abeam the target).

I'm more curious how you're planning to get a 400mm+1.4x lens system stable enough while riding on a boat in the open ocean to be useful.

[ChristopherCoy]

You can always rent a helicopter for an hour!

[RexK_Cozumel]

Originally Posted by Doug Pardee

Let's do the math.

The length of the ship is approximately 1/10th of its distance away—over 500 ft vs. 5280 ft per statute mile. Yeah, yeah, it's probably a nautical mile, but the point is the ship's about 1/10th of its distance away.

So, using a lens with a focal length of "x" mm will result in an image on your sensor that is 1/10th of "x" mm. A 400mm lens will result in 40mm-long ship image. The sensor on a 50D is 22.3x14.9mm. So at 400mm, the sensor will capture about half the length of the ship. At 200mm you'd capture just about a full ship-length (if shot from directly abeam the target).

I'm more curious how you're planning to get a 400mm+1.4x lens system stable enough while riding on a boat in the open ocean to be useful.

I dont think this is correct.

If it were my guess you would need something closer to the 800-1000mm range. There is an article about the 1200-1700mm f5.6-8 that routers used. The lens can fill the frame when photographing a 10 foot area from 1/2 mile away. Of course good luck trying to get your hands on that lens. I believe there are only about 15 in the whole world.

[WooD]

Originally Posted by Doug Pardee

I'm more curious how you're planning to get a 400mm+1.4x lens system stable enough while riding on a boat in the open ocean to be useful.

I've been to Key West several times. Unless there is a storm the waters there are usually like a lake instead of an ocean.

[mtd885]

Originally Posted by Doug Pardee

Let's do the math.

The length of the ship is approximately 1/10th of its distance away—over 500 ft vs. 5280 ft per statute mile. Yeah, yeah, it's probably a nautical mile, but the point is the ship's about 1/10th of its distance away.

So, using a lens with a focal length of "x" mm will result in an image on your sensor that is 1/10th of "x" mm. A 400mm lens will result in 40mm-long ship image. The sensor on a 50D is 22.3x14.9mm. So at 400mm, the sensor will capture about half the length of the ship. At 200mm you'd capture just about a full ship-length (if shot from directly abeam the target).

I'm more curious how you're planning to get a 400mm+1.4x lens system stable enough while riding on a boat in the open ocean to be useful.

As posted above if the conditions are right then it will be like a lake. I'm not an experienced photographer having just returned to the hobby from a 30 year hiatus. It's the only time I will be able to experience this and with the speed of the 50D (6.3fps) I was thinking I could get a nice series of shots of the explosion and sinking. I'm just not sure what I'm going to need to succede. Thanks for your help.