Auto Focus Area

[donkeymusic]

Hello

Have been using the Auto Focus Area setting for use in my practice at the studio.

I presumed if used Wide then this would get as much of the subject in focus??

I also presumed that if i used spot i could select the focus point that was best for the eyes, which i try to focus on? if this is the case and i use spot, focus and the press the button half way down, can i still move the camera to improve composition and not loose the focus on the eyes?

Am i correct in my thinking, what would other use in the studio?

Thanks

 

[donkeymusic]

any assistance?

thanks

 

[donkeymusic]

just thought i would bump this for any suggestions.

cheers

 

[Mahoneyd187]

Hi

The "wide" setting will be a setting that utilises focus points across the width of the frame, in horizontal orientation. It will usually select one focus point where the subject is closest to the camera.

How much of a subject is in focus, is determined by the aperture you're using.

You've mentioned eyes so I'm guessing this is mostly applicable to shooting people.

The focus techniques I use for this are (in order of most common);

Single shot AF, Single focus point. Compose the image, select the single point of focus that's closest to the subjects eye, hold the shutter button half way down to focus, keep it held while you make a minor composition adjustment, then fully depress to capture the frame. This techniques weak points are when using wide apertures and wide angle lenses, when you recompose using either of these, you may drop off focus.

Continuous focus, Single focus point - I use this for shooting kids in the studio mainly, with this you can't recompose as the focus continously tracks, if the kid moves off the focus point, the focus will just go to the background. I just follow them round with the single point aimed at their head and fire as and when I want.

That's for my D200, with more advanced Nikons like the D300S, D700, D3 etc etc you can use dynamic area af and continous focus, which I believe will lock onto a target and track them as they move around the viewfinder? No experience of this but I look forward to having it one day lol

 

[HoppyUK]

^^^ Sounds right to me.

I just use single point AF, nearest point to the nearest eye, hold that with first pressure on the shutter release, recompose as necessary, shoot. And keep checking it because depth of field might be shallower than you think and both subjects and photographers move without realising it!

You also said "if used Wide then this would get as much of the subject in focus??" Not totally sure what you mean by that, but if you want as much depth of field as possible, then you should use a high f/number. Check here to calcualte exactly what your depth of field would be www.dofmaster.com

 

[donkeymusic]

thanks for your replies.

another question, iif i use a single focus point and focus on the eye and re compose, as long as i am still half pressing the shutter button then the eye should still be in focus?

How does this work for full body shots? would i still focus on the eye?

cheers

 

[Mahoneyd187]

thanks for your replies.

another question, iif i use a single focus point and focus on the eye and re compose, as long as i am still half pressing the shutter button then the eye should still be in focus?

How does this work for full body shots? would i still focus on the eye?

cheers

As I said, the weaknesses of focus and recompose are wide apertures (low f number) and wide angle lenses.

As an example, you're up close, say 2m from model with wide lens, crouching down for a full length shot. You focus up on their eye, now imagine a piece of string from the camera to the eye giving an exact distance measure. When you hold focus and recompose down to waist level, imagine whether the string would land exactly on their belly. It wouldn't, it would land slightly beyond. So their face may be in focus but not their body so much, do you will need a narrower aperture to give more depth of focus.

I don't know if that made any sense but I tried lol

Danny

 

[HoppyUK]

thanks for your replies.

another question, iif i use a single focus point and focus on the eye and re compose, as long as i am still half pressing the shutter button then the eye should still be in focus?

Yes.

How does this work for full body shots? would i still focus on the eye?

cheers

Don't worry about it. You always want the eyes to be sharp in portraiture, and usually the nearest eye if you have to choose. But that's only a problem when depth of field is very shallow.

If you are shooting a close head-shot at f/1.4, for a deliberate effect, your depth of field (not depth of focus, that's technically something different) will be measured in mms - see the DOFmaster link above. But with a full length shot the subject is much smaller and depth of field will almost always be enough to cover the whole body. Unless you're shooting from an unusual angle.

It is only with very close, very shallow DoF portraits that you have to worry about focus-recompose technique and tread carefully. The thing is this - with this method you have to angle the camera to check the focus and then move it back to recompose for the framing your want. So the camera will have moved fractionally, and when DoF is just a few mms, it will be out. This is why you always use the nearest focus point to the eyes in a situation like this, to minimise the recompose movement.

In an extreme situation you might need to leave the focus point always over the eyes as you can't afford any movement at all. In which case, move back a little to get some area around the subject, make sure you nail the focus but don't move the camera at all and crop for the framing you want in post processing.