Focus point for sharp eyes, 2 person portrait?

Rocketman1978 · Dec 23, 2012

I have read on multiple occasions that you should focus on the eyes in portraits for maximum sharpness. Well in the case of shooting a portrait consisting of 2 individuals what should your focus point be? Tomorrows pictures consist of my 11 week old daughter and Santa Claus and I want the vast majority of the shot to be in focus.

thetrue · Dec 23, 2012

Smaller aperture (probably f/8ish) with either slower shutter or higher ISO, of any combination of the two.

SCraig · Dec 23, 2012

Check a depth of field chart to see what your DOF is going to be at the aperture you are using. Then make sure that both faces are within that range and you will be good. The closer you are to the subject and the wider your aperture the narrower the DOF will be.

keith foster · Dec 23, 2012

The middle focus point is usually the most accurate focus point on most cameras.

Depending on the situation and how much light is available here are the two situations I would be prepared to do.

1. Use your 70-200 f4 and move back as far as you can. 20-30 ft at least. Set your aperature at F4 and shutter speed to 1/80 or 1/100 depending on how steady of a hand you have.
I would then adjust my ISO till I got the exposure I needed. You can easily do this while you wait in line for your child's turn. You will probably need to start at ISO 1600 and go up
up from there. At 30 feet your depth of field will be 8ft 8in which should be more than enough and 30 ft should be enough to get Santa and child in the shot.

2. Use your 50 f1.4 Set your aperature at f2.8 and get 15 ft away. Your depth of field is 2ft 11in at that distance which will blur the background nicely and let both faces be completely in focus. You can then set your shutter speed higher, like 1/160 or 1/200 then follow the same procedure for ISO.

One other suggestion is make sure Mom is with you to help your daughter transition to Santa. At her age most kids are pretty unpredictable about how they will relate to Santa and you won't be able to do both jobs successfully.

Hope you will share your shot with us when it is taken and let us know what settings you ended up having to do to make it work.

Merry Christmas to you and your family!

Rocketman1978 · Dec 23, 2012

thetrue said:
Smaller aperture (probably f/8ish) with either slower shutter or higher ISO, of any combination of the two.

I'm shooting with my 50mm, was thinking f/8-11 and higher ISO. My thoughts are if I go too slow on my shutter, my daughter will squirm and I'll lose the shot.

So would I use a manual focus point and set it right between the 2 in the portrait?

Rocketman1978 · Dec 23, 2012

keith foster said:
The middle focus point is usually the most accurate focus point on most cameras.

Depending on the situation and how much light is available here are the two situations I would be prepared to do.

1. Use your 70-200 f4 and move back as far as you can. 20-30 ft at least. Set your aperature at F4 and shutter speed to 1/80 or 1/100 depending on how steady of a hand you have.
I would then adjust my ISO till I got the exposure I needed. You can easily do this while you wait in line for your child's turn. You will probably need to start at ISO 1600 and go up
up from there. At 30 feet your depth of field will be 8ft 8in which should be more than enough and 30 ft should be enough to get Santa and child in the shot.

2. Use your 50 f1.4 Set your aperature at f2.8 and get 15 ft away. Your depth of field is 2ft 11in at that distance which will blur the background nicely and let both faces be completely in focus. You can then set your shutter speed higher, like 1/160 or 1/200 then follow the same procedure for ISO.

One other suggestion is make sure Mom is with you to help your daughter transition to Santa. At her age most kids are pretty unpredictable about how they will relate to Santa and you won't be able to do both jobs successfully.

Hope you will share your shot with us when it is taken and let us know what settings you ended up having to do to make it work.

Merry Christmas to you and your family!

Wow thanks for the info! Santa is actually paying a personal visit to the house, which makes for an easier shot, won't have to worry about waiting my turn, etc.

I don't thnk I'll have the option for 30' from subject so I was thinking my 50 would be best option for the shot. I'll definitely try your recommendations, thanks of the help! Merry Christmas to you too!

thetrue · Dec 23, 2012

Oh wow, lucky Santa in the house deal. I was outlining for a quick few shots and run! Keith's suggestions are better since you have the time!!!

KmH · Dec 23, 2012

Unless you have exemplary camera holding technique or are shooting from a tripod, from 20 or 30 feet away using a 70-300 mm lens 1/80 or 1/100 won't be a fast enough shutter speed to ensure the control of camera shake blur, let alone child motion blur. At 20 feet away you would likely have the lens zoomed to about 200 mm and need closer to 1/200 for your shutter speed.

You need to know that depth-of-field produces a zone of sharp focus that is in a plane approximately parallel to the plane of the image sensor in your camera. Each lens will produce some amount of 'field curvature' that make the DoF less than parallel to the plane of the image sensor.

With sufficiently deep DoF, the zone of sharp focus is sufficiently deep enough to have all eyes in focus.

So using a DoF calculator, the total DoF a T3i with a 50 mm lens set to f/8, and point-of-focus (PoF) 10 feet from the camera will produce is 3.77 feet.
However, that total DoF is not evenly distributed in front of and behind the point of focus. The distribution is 41% in front and 59% behind the point of focus.

At f/11 the total DoF only increase 1.75 feet to 5.52 feet, and the DoF distribution gets more difficult to work with at 37% in front of, and 53% behind the PoF.

Derrel · Dec 23, 2012

Set 'er to f/8. Focus on your KID's face. Oughtta' be fine. Shoot from 12 feet away. Use flash to ensure adequate light indoors. Bounce the flash off the ceiling. Have Santa cradle the 11 week-old child in his big arms and hold her up relatively close to his chin. No worries. It'll all be fine. Use the 50mm, and you can crop in a bit later.

keith foster · Dec 23, 2012

KmH said:
Unless you have exemplary camera holding technique or are shooting from a tripod, from 20 or 30 feet away using a 70-300 mm lens 1/80 or 1/100 won't be a fast enough shutter speed to ensure the control of camera shake blur, let alone child motion blur. At 20 feet away you would likely have the lens zoomed to about 200 mm and need closer to 1/200 for your shutter speed.

You need to know that depth-of-field produces a zone of sharp focus that is in a plane approximately parallel to the plane of the image sensor in your camera. Each lens will produce some amount of 'field curvature' that make the DoF less than parallel to the plane of the image sensor.

With sufficiently deep DoF, the zone of sharp focus is sufficiently deep enough to have all eyes in focus.

So using a DoF calculator, the total DoF a T3i with a 50 mm lens set to f/8, and point-of-focus (PoF) 10 feet from the camera will produce is 3.77 feet.
However, that total DoF is not evenly distributed in front of and behind the point of focus. The distribution is 41% in front and 59% behind the point of focus.

At f/11 the total DoF only increase 1.75 feet to 5.52 feet, and the DoF distribution gets more difficult to work with at 37% in front of, and 53% behind the PoF.

You may be right Keith. What I was thinking was since the OP indicated he wanted as much in focus as possible that he wanted to get both Santa full body and child in the shot.
On his crop sensor camera(1.6) at 70mm( equates to 112mm on FF) he would need to be back about 20 ft to get Santa full body and his daughter in the shot. I didn't factor subject motion into my number though and you are right that is going to make a difference and he will need to go up. The problem is unless he has really nice ambient light where they have Santa the OP's ISO is going to get up to 3200 or maybe even 6400 for him to be able to shoot at 1/200 don't you think?
I am not sure how well the T3i handles ISO that high if the OP is planning on printing any of these.

thetrue · Dec 24, 2012

I see a little noise at 6400 in blacks, but not too bad at 3200

t3i here

keith foster · Dec 24, 2012

That is good to know. Thanks for posting that.
To the Op.... With your ISO performance that good I would set you ISO at 3200, f8 and AV mode. If you shutter speed is still not at 1/200 or faster bump your f stop to a faster stop, and try again until you get around f4. If it still isn't the shot you want then take your ISO up.

Or..... Move Santa and your daughter over next to a big window and solve most of the issues we have been discussing.

Rocketman1978 · Dec 24, 2012

Awesome! Thanks Guys!

As far as the time of day, I believe this is all going to happen after dark, I'll light up the area with indoor lighting as best I can but unfortunately the only flash I have is on camera so I don't have many flash options. I haven't shot much with the flash as I'm still learning the other fundamentals.

Last question, to focus on something in particular I compose the shot and the choose the focus point manually- the one closest to the subjects eyes. Is this the correct method? I haven't read a lot on focus, just played with it on my own.

paigew · Dec 24, 2012

Well I would not shoot at f8 I would shoot at 3.2-4. just make sure their faces are on the same plane and you will be good to go!

eta I would set your do to your dds eyes