Choosing a fast lens

[one eye jack]

Please allow me to ask a question. I've been shooting some dance events in dark environment using FF Nikon camera with f2.8 zoom lenses. When shooting wide open at f2.8, I occasionally got some blurred images due to the DOF. If I were to use f1.8 or f1.4 prime lenses, isn't it more difficult to get sharp images? How should I prevent it?

Using faster lens may solve problem of as more light allow autofocus to work.

Your question is different from TS ( he wants to freeze/capture action to get sharp focus).
Whereas you want accurate focus because of shallow depth of field ( DOF) it varies
depending on aperture,subject distance and focal length.Autofocus systems work essentially the
same priciple of contrast difference whether phase or contrast method.Phase measure only
once whereas contrast method take multiple readings so phase is faster.When lighting is
low this means environment is low in contrast so autofocus system start to fail
(focus hunting).

There are two types of autofocus detectors used in DSLR, cross and vertical type,cross
being more accurate.These are located in the central area of the viewfinder and the verticals
around it.It is suggested in situations like low light /contrast you focus on the brightest
part of subject.Lock focus and reframe to take picture.Look for vertical lines in the
picture if there are any you may need to rotate the camera 90 degrees to do it
(if lines are horizontal)and then back again to reframe.Ultimately you may need to focus
manually to get sharp pictures.Selective positioning of focus point/s may also help.

Since flash is not allowed in paid performances ( temporary blinding of performers and
viewer enjoyment) all precautions must be taken to ensure steady hold of camera to avoid
camera shake like triod/monopod ( if can bring in).I don't think you can do anything about
dslr mirror slap even if there is a mirror flipup feature.Here mirroless has the advantage.




http://www.cambridgeincolour.com/tutorials/camera-autofocus.htm

http://jamesaphoto.co.uk/advice/why-manual-focusing-is-still-important/


http://www.pointsinfocus.com/learning/cameras-lenses/brief-history-focusing/4/


http://www.clarkvision.com/articles/understanding.autofocus

 

[ziggy]

The challenge is to balance shallow depth of field with freezing motion with the appropriate shutter speeds and acceptable noise levels.

I shot some dance performances with settings of iso1600-3200, 1/30 f4 burst mode and got some decent pictures. Not tack sharp due to motion but the mood is quite nicely captured. Most are quite useable after editing.

If you hope to take concert type photos, with less noise/lower iso, then wait for spotlight to fall on the singer, for the singer to be moving less, faster lens and burst mode.

 

[daredevil123]

The USB dock right?

AF finetune on your camera body.

 

[rainduet]

AF finetune on your camera body.

not sure if my camera has this feature..