Focus thoughts and other random questions from a noob

[Flukester]

Hi all

I just invested in a speedlite 430ex and we tried to use it in anger in dark kids play area and the Camera in aperture priority was refusing to take photos.

It turns out it was because it was locked out as not getting focus... And focus mode had to be in one-shot AF for the IR on speedlite to work (up till now we have always used single point servo AF)

Anyway to the question, what focus mode do you use for portraits or people posing for a photo, ie not moving

I'm guessing single point one shot focus, then shifting the focus point around if need be. Manual focus is way to hit and miss, at least with my eye site.

I guess for kids running around everywhere you would be best on multipoint auto focus ?


One more question, in aperture priority if taking a photo of a group of say 10 peolpe, would using f2.8 narrow the depth of field to much and leave some out of focus ?, if so what f stop would you use in a average lit room... With gentle fill flash bounced from ceiling. I'm not sure there is a definitive answer... But it seems to me I have a bad habit of cranking the aperture wide open, when more depth of field would probably of created a nicer photo as you can see other things in the frame clearly.

Oh and another question, how often do you use exposure compensation setting ?, I'm guess this is for when you want to override the camera brain without resorting to manual mode.

This photo malarky is dam complex....

 

[SDK^]

Flash works in two ways.

Mode TV, Av, : fill flash.
The flash exposes for the foreground and the camera exposes for the scene. This may mean in a dark room indoors you may get blurred subjects in TV mode due to the camera setting the shutter speed low, or, underexposure in Av mode because your aperture is maxed out and won't go any wider.

Mode M
You set the shutter and aperture values and the flash exposes for the scene. This work best indoors. Start at 1/100 and F8 and adjust as appropriate. The higher you set ISO the less reliance there will be on the flash to light the scene.


Read these guides for a complete Canon flash guide (I'm assuming your shooting with a Canon system)

http://photonotes.org/articles/eos-flash/
http://photo.net/equipment/canon/guide-to-canon-speedlites/

 

[theheyes]

It is complex, but you're asking the right questions.

In my opinion as a photographer you should be checking your exposures (and by extension your compensation) constantly. Learn to read the histogram and turn on your highlight warnings and these will help you do it at a glance. Also remember it's just as important to remove any exposure compensation when you move or the scene changes. For that reason alone you should make it a habit to check.

And F2.8 for groups is just a no. There is that mentality of being a bit obsessive about those large apertures, especially since you've probably paid big money for them, but your smaller apertures are there for a reason. For groups, at bare minimum you need the main subject(s) (e.g. bride/groom/birthday girl) in sharp focus or the eyes of the front row of any given group so choose your point of focus carefully. It does vary with focal length, however. So what you may get away with wide at F4 might not necessarily be true at longer focal lengths.

Ideally you want everybody in good focus, so F7.1, F8, whatever it takes. Be careful when bouncing your flash, too, as with a myriad of bodies and limbs you need to be mindful of casting unsightly shadows on faces. You've probably read about a 1000 times not to point the flash in the direction of the lens, but if you need the light then you need the light. You can override those rules like you override your camera's metering system.

Just keep practising.

 

[An Exception]

When you understand the relationships of focal lengths and DOF's, you will know when you can shoot group shot's at F1.4 or wider.

 

[Flukester]

Thanks for replys, very helpful

 

[unrealrocks]

When you understand the relationships of focal lengths and DOF's, you will know when you can shoot group shot's at F1.4 or wider.

At 85mm and a good distance from your subject you can get way with it like above but I doubt the indoor area Flukester is referring to will allow him quite as much space

http://www.dofmaster.com/dofjs.html is a useful tool if you aren't sure. Just experimenting rapidly teaches you what sort of aperture you can get away with. That said this is all relavent taking 'correct' photos. No one said photos have to be in focus