Flash shadow...what did I do wrong?

[Hazey]

I had my first try at some flash portraits. 430EX on 40D with sto-fen diffuser. I couldn't find a single shady spot without speckled sun which I know is a drag but decided to have a go anyway.
ISO400 1/250 F/8 and I *think* I had the flash on 1/8 but can't remember...it's a pain that flash seetings aren't in EXIF!

Anyway..it seems the flash was too bright as I now have a shadow on the rear child...but when I dialed it down another stop on the flash it was too dark.
Any advice? Was I too close? I am wondering if this was the problem as I was only 5 feet away and using a 17-55 at 55mm. The rear child is OOF too...is this because I was too close for F/8 to get them both in focus?
Any help appreciated.

[tdodd]

For this particular photo, turn the camera round so the flash is on the other side. That way the flash will reach around the face of the child in front, lighting the child behind. The flash shadow will fall on the distant background, over on the right of the picture, where it will probably not show up at all. You'll still get some shadowing under the arm but no worse than you have now, and the face will be fixed.

The more complicated option is to use a large softbox or brolly to soften the light and reduce the hard edges to the shadows, but you'll still need to bring the light source left of camera to fill around the ahead of the child in front.

[sando]

Anyway..it seems the flash was too bright as I now have a shadow on the rear child...but when I dialed it down another stop on the flash it was too dark.
Any advice? Was I too close? You weren't too close. The flash was operating as the main light-source, it seems, rather than fill. I would normally go manual, and manual on the flash in this situation, if you want to force the flash to be as fill. Chimp, chimp, chimp and you'll get better at judging these situations. You could surely see after you'd taken this that it wasn't as you'd wanted it?

I am wondering if this was the problem as I was only 5 feet away and using a 17-55 at 55mm. The rear child is OOF too...is this because I was too close for F/8 to get them both in focus?
Any help appreciated.f/8 and being quite close to them may mean that the person in the rear was OoF, yes. Try moving further away or jusing a narrower aperture.

[thebishopp]

In addition you could also use a slower shutter speed to slightly blur the background rather than larger aperture . You would use the flash to "freeze" your subject and keep them sharply in focus while still getting a nice bokeh for the background (the slower shutter speed would allow your hand "shake" to slightly blur the background).

[Hazey]

Sando..I was using manual...both on the camera and the flash. I am still learning the how to's and where fors of how it all works.
I didn't notice the shadow on the LCD...it was stressful enough just trying to get both kids looking my way and I didn't have a great deal of time to evaluate the shots at the time which is why I am trying to work out what I did wrong now.
I think tdodd has the main solution here and looking back...I did tip the camera on it's side for this shot which put the flash on the wrong side of the raer child....I didn't think of that so thanks. If I had tipped the camera the other way then I would have lit up more of the child behind. I do hope to get a softbox going in the future but it's not within my budget at this stage.
Sando, you are right that the flash ended up more as the main light than fill...I needed to dial it down a stop it seems....and as the bishopp suggested, slow the SS down a bit more.
Thanks for the suggestions...I'll have another go at it soon.

[Gatorboy]

I had my first try at some flash portraits. 430EX on 40D with sto-fen diffuser.

What were you thinking you were going to bounce off with the stofen? Outdoors, put that thing in your pocket.

I would have shot this manual, with proper exposure and use my on-camera flash at -2 FEC.

[Hazey]

Gatorboy....I am not you. And I am learning. I know there is a debate about the merits of using diffusers outdoors but the lady who advised me to use it for the kids portraits has been taking outdoor portraits for many years and says that although you are wasting some of the light, the flash needs to be softened or it's too stark. I decided to use it to see for myself. The flash would have blinded these kids without it.
I WAS using manual...and I did my best at proper exposure and yes it's a little overexposed.
Your words were written in a condescending manor and did nothing but get my back up. If you can't say anything helpful or offer well meaning advise the don't post!

[tdodd]

Hazey, you create "soft" light by making the source of the light appear larger. If you imagine a very small light source - a simple bulb, the shadows it casts are deep, with well defined edges. That is know as "hard" light. In the home, you put lampshades over your bulbs. This softens the light by blocking the direct light from the bulb and spreading the light over a wider area.

In order to make "soft" light from your flash gun you need to find a way to make the light source appear bigger. You can accomplish that several ways. One is to fire the flash into a softbox, with a large frontal surface area. Another is to fire it through an umbrella or bounce it off a brolly or reflector. The flash head itself is pretty small, so the light from it is pretty hard. When you put a Stofen Omnibounce onto the flash head it barely changes the size of the flash light at all. Any light coming directly from the Omnbounce will create shadows just as hard edged as the bare flash head.

What makes an Omnibounce work, indoors, is that it spreads all over the place and then bounces back onto yout subject from all around the room. Thus you create an enormous light source from your tiny flash. This is what makes bounced flash such a wonderful thing, and why the little popup flash is so often scorned - it can't (practically) be bounced, and is very tiny indeed, leading to extra hard shadows. Also, being right next to the lens it gives very flat lighting, concealing the contours of your subject, as there are no shadows and subtle lighting variations across the subject - everything gets hit with equal amounts of light.

Outdoors, things are different. Nature does not typically provide any surfaces for the flash to bounce off and return to your subject, other than the ground. You probably don't really want a green cast reflected up from the grass and a nice illumination under the nostrils. So, when you use the Omnibounce outdoors what do you really achieve? Pretty much nothing. You block and absorb some of the light from the flash head, and cast a load more off into the wilderness, making the flash work hard to illuminate your subject. All that does is drain batteries faster. You will not succeed in making the light softer because you will not have increased the size of your light source and the shadows ill be just as hard edged, flat and unpleasant as before.

If there is nothing to bounce off there really is nothing to be gained by using an Omnibounce, but there are some losses to be made. Save it for indoors, or perhaps near a wall or in a tunnel or archway or something (but watch for a colour cast off odd coloured surfaces). In open air it will do nothing.

[AB8ND]

Remember the 55mm lens on a 40d (cropped body) is equivalent to something like 85 or 90mm which have a rather short depth of field making them good portrait lens. Thus, at 5 feet and f/8 you probably where a bit short on DOF, you could try to focus between the 2 wonderful subjects, but then you might not have either sharp. This is always a probably with group or couple portraits.
Even with the Sto-fen your flash is still a very small light beam, soft or not, causing the shadows. I'd try to bounce it off something, maybe some white foam core or poster board, a sheet etc. You can have a VAL (strobist for voice activated lightstand - person) hold the bounce surface off to the side or even behind you. Things you might look at are a 5in1 reflector or an umbrella, these, beyond there intended purpose work great for bouncing.

Jack

[sando]

I tend to find, also, that in a situation like this, focussing on the rear-most person rather than the front-most person helps get them both in focus.

[umphotography]

when i 1st saw the pic first thing that came to my mind was you shot in manual mode. nothing wrong with that but w/o metering i also tend to over expose doing the same thing. im thinking you would of had better results shooting with the flash in ettl mode. for that shot im guessing about about 3.5-4.0 to get some background blur,, drop the flash output about a 3rd and maybe a little different position to compensate for the sun hitting the subject. the camera will do the rest of the work for you. try manual mode, shutter speed at 125-200,f stop that you think will work best( i always meter), camera flash in ettl and bingo..you will have a keeper in most cases.

i also use a diffuser when shooting outdoors to soften the light. nothing wrong with that imho.i purchased the gary fong product. the video that came with his products has alot of good information in it. he has no problems with using his diffusers on just about anything that requres light. im not buying the put the diffuser away for outdoor work one bit. my diffuser almost never leaves my flash and i get pretty good results.

i also took alot of guys advise and made up a home made diffuser for shooting and spreading light outdoors. costs about 8 bucks and works awesome. or you could buy one from b&g for about 80.00 that looks really trick and does the same thing.

[SkipD]

Gatorboy....I am not you. And I am learning. I know there is a debate about the merits of using diffusers outdoors but the lady who advised me to use it for the kids portraits has been taking outdoor portraits for many years and says that although you are wasting some of the light, the flash needs to be softened or it's too stark. I decided to use it to see for myself. The flash would have blinded these kids without it.
I WAS using manual...and I did my best at proper exposure and yes it's a little overexposed.
Your words were written in a condescending manor and did nothing but get my back up. If you can't say anything helpful or offer well meaning advise the don't post!I don't thing Gatorboy was writing in a condescending manner. He was just pointing out fact and trying to get you to think of the physics of light control.

The "tupperware" diffusers are, in my opinion, quite useless outdoors. What would work much better outdoors is a (much larger) reflective bounce card type of device.

What would also help is to get the flash off the camera and onto a bracket that keeps the flash above the lens regardless of camera position unless you are working with the camera strictly in the "landscape" position.

[Apone]

The "A better Bounce Card" gets my vote for this situation. The feathered version works quite well for keeping hot spots off of faces and you can make a few of different sizes to do whatever you need them to. Plus they are super cheap to make.

[NeutronBoy]

maybe simply shifting the baby to the right a bit more could have prevented the shadow. Have the older child lean her head forward to get the two noggins aligned with each other.

[thebishopp]

The "A better Bounce Card" gets my vote for this situation. The feathered version works quite well for keeping hot spots off of faces and you can make a few of different sizes to do whatever you need them to. Plus they are super cheap to make.

He can make one using either a simple white index card rubber banded to the flash or he can make one using those white foam sheets at walmart in the craft section (or other craft store).

He can also use it in conjunction with his stofen style difusser. You put the "stofen" on then you rubber band the index card to the back to help direct more light forward. I've actually done this and it's not bad.

In fact here is a picture using that method (index card was bent backwards at about a 45 degree angle to reduce how much light was redirected forward and the "stofen" difusser was on to help soften the light):

[Hazey]

tdodd, I appreciate your explanation of why the diffuser is a waste of time outdoors, and I can see that this may well be the case, but I also know there are diehards who insist it does help soften the light and wouldn't do outdoor portraits without one....(like slowdad). However, I can see what you mean and it does make a lot of sense and I will see if I can source a softbox that won't break the bank. Being new to flash use, I can't afford to discount any advice and will try everything and anything to improve my outdoor flash photography.:)

Neutronboy..that would have been another good alternative...but these kids were like worms and the older wasn't really old enough to follow instructions...she didn't like the camera full stop...think she was a little scared of it and can't blame her really.I shot these frames between tears and bribery from mum...who was placing jelly beans in their mouths to keep them happy....which was a bad idea in hindsight as the best shots have mouths full of coloured goop...but you live and learn!

Slowdad...what did you use to make your 8 buck diffuser? I'm all ears.:)
I'll go search for this 'better bounce card' too.

Skip...if Gatorboy had backed his comments with an explanation that was helpful..all would be peachy.....he just said the stofen was a waste of time but didn't explain why. I know my exposure wasn't great here...even though I actually did meter..but the flash overpowered the ambient. I know in text that meaning can be misconstrued but I just didn't find the comments helpful.
Appreciate all the comments..I have a few things to try now.
Many thanks,
Hayley (Hazey)..who is very much 'she', not 'he'.:lol:

[krb]

but the flash overpowered the ambient. Maybe that's why gatorboy said he'd have shot it with -2 FEC... ;)

[Mark1]

... the flash needs to be softened or it's too stark. I decided to use it to see for myself. The flash would have blinded these kids without it.



Sorry to jump in late hete, but you are confusing a few points. The brightness of the light is different from the softness of the light. There is Bright/dim light, that is is the intensity. Then there is hard/soft light, this is determined by how it produces shadows. Hard edged shadows is (obvoisly) hard light.

The Sto-Fen does not darken the light ( well not really) so you would have blinded them just as much with it as without it. The Sto-fen is a attempt to soften the light by trying to make the light scorce bigger. However it is not really much bigger than the flash head it self, so you wil get minimal results.

That said.... The softness of the light is created by the relationship in size of the subject and the light scorce. The distence from the subject is also part of the formula. A 4 foot square soft box is not very soft, if you use it from 75 feet away. But move it close where it can light the front, side, and back, and it is very soft. So soft, you will probably not have any shadows.

Now to my point. take a few minutes to plan and set up your shot. I would re-shoot your shot by hanging a white sheet from something, angeled such, so when you turn your camera on its side to take the picture, you can fire the flash into the sheet and the sheet will reflect it to the kids. If you have to, the TTL will still work. Doing this, the apparent light scorce is no longer a tiny point, but a large area. This will soften the light a lot. I would also time it to early to mid evening So the flash is the main light not the sun.

[red_click]

Would a GF Lighsphere be better for outdoors?

It's not big compared to an umbrella but it does seem to be bigger? So would it be better up close? Or still not worth it?

[René Damkot]

the "stofen" difusser was on to help soften the light):

I'd think all the stofen did here was give you a harder shadow on the BG...

[NeutronBoy]

...but these kids were like worms Been there before!! Good luck!!

[Titus213]

Would a GF Lighsphere be better for outdoors?

It's not big compared to an umbrella but it does seem to be bigger? So would it be better up close? Or still not worth it?

No, it is marginally bigger but light can't be directed out of it. These tupperware devices are made to bounce light all over a small room, not a backyard.

[Hazey]

Yes Mark 1...that makes a lot of sense too...thank you.
I will try the sheet idea...sounds like a good one.

[Wilt]

http://farm4.static.flickr.com/3080/2596686949_4a9cd98415.jpg

As can be seen from the relatively hard edges of the shadows, putting the Stoffen on does very very little to 'soften' direct light. Stoffens accomplish softening primarily via scatter of light in all directions so that it then bounces off nearby walls and the ceiling...effectively turning THEM into larger light sources.

These shots show the effect of native flash lens vs. something that is the same size (like the Stoffen) without any bounce effect vs using something even as small as a 5" x 7" source...

native lens...
http://i69.photobucket.com/albums/i63/wiltonw/Lensonly.jpg

Stoffen-sized 'diffusion'...
http://i69.photobucket.com/albums/i63/wiltonw/Papercover.jpg

5x7" softbox...
http://i69.photobucket.com/albums/i63/wiltonw/10footsoftboxb.jpg

[hastur]

Hazey,
I spend a lot of time chasing a 4yr old and a 2yr old around the yard with my 20D and 17-55. I wouldn't think of taking a picture w/o the flash unless they were so far away that it wouldn't reach.

I shoot most of my pictures in Tv mode with a SS of 1/250 (to try to stop fidgeting) and FEC = -1 to -1.67. I put the kids with their backs to the sun so they don't squint and I can use the flash as fill. The camera will adjust the aperture as needed to make the exposure correct. You will have to determine if this is correct for your particular needs, but it does save chasing the meter manually in a dynamic situation. Adjust the ISO to drive the aperture for more or less depth of field and use EC to lighten or darken your background.

I believe the harsh shadow was made more noticeable by the power of flash as well as it's size. You can adjust the power without changing any equipment by using FEC or knocking the power down from 1/8 to 1/32 or 1/64. My youngest also has very light skin, which makes the near blowout quite common, especially if the background is dark. So I have to chimp and keep an eye on the "blinkies". The camera meters for the whole image, so it tries to bring the background exposure up at the expense of your subject, especially the one if front. The one in back is saved by light falloff. Maybe you can put the light skinned one in back?

Manual control is great if you control all of the conditions, I can't control all of the conditions chasing kids, so I use the automation.

Try Chuck Gardner's website, especially the one about setting exposure using a white towel. Here's a start http://super.nova.org/DPR/FillFlashTest/ He has a wealth of knowledge there.

Above all, have fun.

Rob

[thebishopp]

As can be seen from the relatively hard edges of the shadows, putting the Stoffen on does very very little to 'soften' direct light. Stoffens accomplish softening primarily via scatter of light in all directions so that it then bounces off nearby walls and the ceiling...effectively turning THEM into larger light sources.

These shots show the effect of native flash lens vs. something that is the same size (like the Stoffen) without any bounce effect vs using something even as small as a 5" x 7" source...

native lens...


Stoffen-sized 'diffusion'...


5x7" softbox...


To be fair that pic I used as an example had quite a bit of contrast boosting and processing :-) (I just grabbed one from the set I used the stofen and index card on that I had available on my flickr)... but I do like your example using the rulers. While the stofen light is 'softer' than direct flash, the softbox is clearly better for the purpose.

[sapearl]

I may have missed it in all the text, but has anybody suggested using a flash bracket here?

Hazey, judging by the shadow I'm guessing you held the camera in portrait position with the flash head positioned to the right of the camera body. That would cause the shadow to fall across the left side of the child which is what we see. A bracket that allows you to keep the flash top centered will greatly reduce any shadowing.

Btw, VERY cute kids :D

[SkipD]

I may have missed it in all the text, but has anybody suggested using a flash bracket here?Yup.... Post #12. :p

[Jim M]

I have been in many situations where I didn't have a bracket handy, but the flash lives in my photo vest. The simplest solution for the OP is to tilt the camera the other direction to make the shadows fall to the left (viewer's right) of the younger child. The only shadow visible will be one under the younger child's armpit. Once you start thinking about which way the shadows will fall, you can squeak by without a bracket many times. And I couldn't agree more with the people saying that those "Tupperware" diffusers are essentially worthless at normal shooting distances without walls to bounce from.

[Wilt]

To be fair that pic I used as an example had quite a bit of contrast boosting and processing :-) (I just grabbed one from the set I used the stofen and index card on that I had available on my flickr)... but I do like your example using the rulers. While the stofen light is 'softer' than direct flash, the softbox is clearly better for the purpose.


I think we need to be precise in our observations to others about the effects of a light modifier...

'softness' pertains to the transition zone from shadow to light, the 'edge'

'contrast' pertains to the degree of difference in density of shadow to light

Using those terms, my example and the Stoffen shot both show little to no 'softness' change, but some observable change in 'contrast'

[thebishopp]

I think we need to be precise in our observations to others about the effects of a light modifier...

'softness' pertains to the transition zone from shadow to light, the 'edge'

'contrast' pertains to the degree of difference in density of shadow to light

Using those terms, my example and the Stoffen shot both show little to no 'softness' change, but some observable change in 'contrast'

Agreed. Very good example.

[Jim M]

I think we need to be precise in our observations to others about the effects of a light modifier...

'softness' pertains to the transition zone from shadow to light, the 'edge'

'contrast' pertains to the degree of difference in density of shadow to light

Using those terms, my example and the Stoffen shot both show little to no 'softness' change, but some observable change in 'contrast'
I'm going to guess that if Wilt had done his test outside, you wouldn't even have seen the drop in contrast.

[Wilt]

I'm going to guess that if Wilt had done his test outside, you wouldn't even have seen the drop in contrast.

No more guessing needed, Jim. There *is* a drop in contrast simply because the flash serves as fill!

no flash
http://i69.photobucket.com/albums/i63/wiltonw/IMG_1050-1.jpg

flash with native lens
http://i69.photobucket.com/albums/i63/wiltonw/IMG_1052-3.jpg

flash with Stoffen-sized diffuser, direct
http://i69.photobucket.com/albums/i63/wiltonw/IMG_1051-2.jpg

Shots have the ruler all at the same brightness levels, analogous to having a subject's face at the proper level of exposure.

[Mark1]

In door or out door, light reacts the same. Light does not change its properties because it is in a confined space. Laws of physics don't really care if it is in or out. The same results can be expected where ever you do a "test"

[Hazey]

Thanks to all that have read and offered suggestions...I have found the thread to be extremely informative and helpful.
It seems that my main problem was that I tipped the camera to the right in portrait position rather than to the left...which is merely lack of experience and foresight on my part. I didn't even twig to that while I was scratching my head when viewing that shadow afterwards...but of course it's very obvious now.
Rob (hastur) thanks for sharing your settings with me...I will certainly try that. I was actually changing the FEC frequently whilst taking these photos, trying to get a result that looked natural in my LCD. So in the end I had no idea what I had it on for this photo. It's a shame that EXIF only shows that flash was fired.
Wilt...your samples were very worthwhile to me as I am a visual type person...thank you for posting them. I will leave the sto-fen at home next tome and just make sure the flash is not overpowering.
Tim...a flash bracket will no doubt make it onto my wishlist before long.
Many thanks to you all.
Hayley

[Hazey]

Oh...can I just ask...what is 'native lens'?

[krb]

Oh...can I just ask...what is 'native lens'?
I was wondering the same thing. I assume he his referring to the lens on the flash and saying that nothing additional was added to either diffuse or focus the light.

[Wilt]

I was wondering the same thing. I assume he his referring to the lens on the flash and saying that nothing additional was added to either diffuse or focus the light.

Right

[Curtis N]

In door or out door, light reacts the same. Light does not change its properties because it is in a confined space. Laws of physics don't really care if it is in or out. The same results can be expected where ever you do a "test"All this is true. The difference between indoor and outdoor use of flash is related to the presence or absence of a white ceiling to bounce light.For this particular photo, turn the camera round so the flash is on the other side.This is the best suggestion that has been offered so far and bears repeating. Having the subject hold the baby on the other knee also would have solved the problem.

Learning to think about the geometry of the situation and predict where your shadows will fall is a skill that comes only with lots of practice. For this shot, I tilted the camera clockwise to get the flash camera right. Otherwise, it would have made a shadow to the right of her hat brim and on her body behind the mug.

http://performancephoto.smugmug.com/photos/363211174_Xd9Mo-L.jpg

[thebishopp]

Nice shot curtis.

[Gatorboy]

Light itself is not hard or soft. It's photons flying through the air in a straight line. And the only way to create softer shadows is to make the apparent size of the light source larger.

A piece of translucent plastic that scatters light in all directions does not accomplish this without nearby surfaces (walls, ceilings, etc.) to reflect the scattered light back into the scene and wrap around the subject. A diffuser outside simply wastes light, reduces range, slows recycle times and eats batteries.

There are those that "think" using one outside is helping, but they are simply incorrect.

[sandpiper]

I tend to find, also, that in a situation like this, focussing on the rear-most person rather than the front-most person helps get them both in focus.

Surely that would put most of your DoF behind both subjects and make it harder to get them both in acceptable focus.

DoF extends twice as far behind the focus point as it does in front so, if we assume that DoF at the aperture and distance being used is 18", that gives you 12" behind the focus plane and only 6" in front of it.

Focusing on the eyes of the front child, would give 12" behind them in which to get the rear child acceptably sharp.

Focusing on the eyes of the rear child, would only leave 6" in front to get the front child acceptably sharp, with quite a bit of wasted DoF behind them. So the two sets of eyes would have to be within 6" of each other (from the camera) to get them sharp enough.

You could of course focus on (say) the ear of the front child, to put the focal plane somewhere between the two pairs of eyes, however I would rather have the nearer eyes as the point of maximum sharpness in most situations.

[Wilt]

DoF extends twice as far behind the focus point as it does in front so, if we assume that DoF at the aperture and distance being used is 18", that gives you 12" behind the focus plane and only 6" in front of it.

This is a widely spread fallacy! If you use a DOF calculation program, one finds that a macro distances the DOF is about 50:50, at a single specific distance it is 35:65 as stated, and that it can in fact go more than 5:95 So if you merely follow the simple rule of thumb, your DOF is quite out of whack!

[Jim M]

No more guessing needed, Jim. There *is* a drop in contrast simply because the flash serves as fill!

no flash


flash with native lens


flash with Stoffen-sized diffuser, direct


Shots have the ruler all at the same brightness levels, analogous to having a subject's face at the proper level of exposure.
I'm sorry for not making myself clear. I was assuming dark room and dark outside where the flash was the ONLY component of light. Obviously, the whole reason for using flash outdoors in daylight is to reduce contrast by lighting up the shadows. In your first set of examples the Stoffen-sized diffuser had lower contrast than the direct flash and my presumption was that this was caused by light bouncing off the walls. I also presumed that ambient light was not adding to the exposure. Perhaps I was wrong. However, I think the main point we agree on is that using a Stoffen-sized diffuser outdoors in the open is an exercise in futility. Not everyone agrees with this, but I challenge them to prove it.

[Jeff]

Isn't this a good scenario where the modelling light function could be used?

http://photonotes.org/cgi-bin/entry.pl?id=Modellingflash

[sjlund]

This is a widely spread fallacy! If you use a DOF calculation program, one finds that a macro distances the DOF is about 50:50, at a single specific distance it is 35:65 as stated, and that it can in fact go more than 5:95 So if you merely follow the simple rule of thumb, your DOF is quite out of whack!

At the above stated 5 feet/55mm/f8, the DoF is 46% front, 54% behind, so 35/65 is definitely not a 'rule'.

DoF was also about 9 inches. Moving up to f/11 gives nearly 13.

[john123]

Lots of useful info here, much appreciated.

[sandpiper]

This is a widely spread fallacy! If you use a DOF calculation program, one finds that a macro distances the DOF is about 50:50, at a single specific distance it is 35:65 as stated, and that it can in fact go more than 5:95 So if you merely follow the simple rule of thumb, your DOF is quite out of whack!

Okay, so the exact math may be a little out. My point is still perfectly valid, there is still more of the DoF behind the focus plane than in front (we're talking portraits not macro, so the 50:50 isn't valid in this case).

My comment was that focusing on the rear child will NOT make it more likely that both will be in focus, for the reason stated above. The exact percentages are not critical to the principle.