Which Lense would you use here?

[etrust]

Hi,

I have shoot last week a music video where girls was dancing. I Used a 7D and a 17-55mm 2.8 lens.

I had a Problem with close ups because the Girls was moving and I everytime lost the focus.

What the solution to avoid this problem? Should I take another lens or tell them to not move..hahaha

 

[pianoboy]

Close down the aperture and it'll be easier to keep focus. Or, you can adjust focus to follow them while they move.

 

[David G. Smith]

Well, your issue is with the depth field. Depth of field is a function of sensor size, lens focal length aperture size, and subject camera distance. You can't do any thing about the sensor size, except change cameras. To control depth of field, you need to adjust your lens focal length, the aperture or subject camera distance. The wider your lens and the smaller your aperture (higher F #s) the larger ,or deeper, your depth of field. To control the aperture the best way is add more light. Of course you can affect exposure by increasing ISO, and shooting at a slower shutter speed, but this is not recommend. Increasing the ISO increases the noise in the image and shooting at a slower shutter speed will cause motion blur. When shooting video (at 24fps) a shutter speed of 1/50th a second is recommended.
Going to a wider lens also gives you a deeper depth of field. However, this does change the angle of view of the shot.
Now increasing the depth of field does change how a shot looks and with a deeper depth of field, more of the background my be in focus.

Of course the best answer is to rehearsing with the dancers so you get an idea of how they are going to move and you can adjust your focus accordingly.

Here is place you can find make custom depth of field tables, to print out and keep with you.

http://www.dofmaster.com/doftable.html