Focusing on multiple subjects

[CLJphoto]

I just took pictures for my friends engagement. I used a 50mm 1.8 lens on a Nikon d800. For this shoot I shot in aperture priority mode. I shot in AFS-s single point focus mode. When my subjects were close to each other I did not have a problem with focusing on both of their faces. However, when their faces were not right next to each other, only one face was completely in focus.

In the picture below the mans face is slightly out of focus. I know this is probably a depth of field issue because he was closer to the camera, but where am I suppose to focus to get them both in focus.

F 3.2 ISO 1000 Shutter 1/400sec



I also have an 85mm 1.8 lens and a 28-120 f4 lens in my bag. Would there be a benefit to using either of these lenses.



F 3.2 ISO 1000 Shutter 1/400

 

[steephill]

Simplest solution is make sure they are both the same distance from the camera. Failing that then you need to look to depth of field to help you out. There are lots of calculators around which will give you numbers but the bottom line is you will need to use a smaller aperture to gain depth of field.

In your example you could safely drop the shutter speed by two stops to allow you to close the aperture by two stops increasing depth of field. I would also have tried dropping the shutter by three stops and dropping ISO by a stop as well as the aperture change. If camera shake becomes an issue then use a VR lens and take multiple shots to increase the chances of getting a sharp shot. Or better still use a tripod to eliminate camera shake altogether. You will still have to contend with subject movement but they are in a static pose so that shouldn't be a big deal.

 

[Dan Marchant]

As you yourself pointed out it is primarily a DoF issue not a focus issue. At f/3.2 the DoF is going to be far too thin to reliably get two people in focus - unless, as mentioned above you line them up so they are both exactly the same distance from the lens. Narrow DoF is fine if you are in a controlled (posed) situation* with time for chimp/re-shoot but if you are shooting candids or in a time critical situation you really need to stop down.

Having said that, as a general rule, there will be a greater area behind the plane of focus that is acceptably in focus than there will be in front of it. Therefore if you focus on the closest subject you are more likely to get both people in focus.

* Even then you have to be very careful because a shot viewed on the LCD will look in focus. You need to zoom in and pan around to check that both/all subjects are acceptably in focus.

--
Dan
-
f/2.8 is a smaller number than f/22 in the same way that 100 is a smaller number than 20.
I am learning photo graphee - see the results at www.danmarchant.com

 

[hotdog321]

Three things can help in these situations:

1. get the two subjects in the same plane of focus--the identical distance from the camera.

2. use more depth of field.

3. manually focus on one face, then the other, then split the difference.

 

[canuck dave]

Yes, this is one of the greatest misconceptions about (the value of) multiple focus points. No amount of technology can correct for lack of DOF and/or having multiple subjects in differing focus planes.

 

[AnthonyL]

hotdog321 wrote:

Three things can help in these situations:

1. get the two subjects in the same plane of focus--the identical distance from the camera.

No - the plane of focus is NOT identical distance from the camera otherwise the photo of a brick wall head on would not work.

To the OP - there is only one plane of focus that goes through the point you've focussed on. Imagine a sheet of glass projecting out from your sensor and stopping where your focus point is. Everything on that sheet of glass will be in focus. Everything in front or behind will be out of focus. How much out of focus depends on your aperture. A small aperture (f/16) and a fair bit in front and behind will be acceptable. A large aperture (f/2.8) and just about anything away from the plane of focus will be blurred. Have a play on http://www.dofmaster.com/dofjs.html

So either get all your subjects in the same plane and/or use more DOF.

 

[Joseph Mama]

When he talks about distance from the camera, I believe he means TRUE distance to the camera. A part of a brick wall that is right in front of the camera is going to be closer than the same brick wall off to the right or left.

Thus you have to take the radial distance into account, not just distance from camera to a perpendicular focal plane, right?

Hence, to get both subjects in focus you cant just focus on one of them and hope for the best. You'd have to move the camera inbetween them so they are equi-distant from the camera then use manual focus to focus both of them.

OR, change your depth of field. If you wanna preserve the bokeh, get back a bit and zoom in some (or change to a longer lens). That way you get more depth of field, but still magnify your background bokeh even though it is lessened.

 

[olliess]

Joseph Mama wrote:

When he talks about distance from the camera, I believe he means TRUE distance to the camera. A part of a brick wall that is right in front of the camera is going to be closer than the same brick wall off to the right or left.

Thus you have to take the radial distance into account, not just distance from camera to a perpendicular focal plane, right?

No, I think he really means the distance to the "plane" of focus. The idea, anyway, is to project a sharp image of a flat object onto a flat sensor. That way you can take a picture of a brick wall (or more likely, a building face) or a lineup of people and expect it to be more-or-less in focus across the frame.

 

[olliess]

Dan Marchant wrote:

...as a general rule, there will be a greater area behind the plane of focus that is acceptably in focus than there will be in front of it. Therefore if you focus on the closest subject you are more likely to get both people in focus.

hotdog321 wrote:

3. manually focus on one face, then the other, then split the difference.

Both good bits of advice.

A useful trick for autofocus is to find objects to focus on that are at the distance one wants. In the example, along with stopping down to get more DOF, one could experiment by focusing on the far edge of the gentleman's face or even on part of his far shoulder, or the lady's near shoulder.

 

[Joseph Mama]

Couldn't you move the camera (step over some) so that it is right in front of subject #1 then focus on them? Once focused, you'd move back to where you were.

That way they would both be in the same plane of focus?

If your camera is inbetween the subjects and you turn to focus on one of them, once you turn the camera you've effectively put your plane of focus a bit behind the subjects due to the longer distance due to curvature. Is that correct?

 

[Leonard Migliore]

Joseph Mama wrote:

Couldn't you move the camera (step over some) so that it is right in front of subject #1 then focus on them? Once focused, you'd move back to where you were.

That would work if you were on rails. Otherwise, you tend to wander off a straight line.

That way they would both be in the same plane of focus?

Maybe. I'd set up the camera so I had some depth of field and didn't have to worry about geometry.

If your camera is inbetween the subjects and you turn to focus on one of them, once you turn the camera you've effectively put your plane of focus a bit behind the subjects due to the longer distance due to curvature. Is that correct?

That's correct. I still would stop down enough that it didn't make any difference.

 

[Aberaeron]

It is ironic [or something] that if a small sensor cheap point-and-shoot were used in 'auto' mode, both subjects would have been pin-sharp.

To get both in focus using your kit would need a substantially stepped down aperture. F16 perhaps.

Absolutely nothing wrong with using 'auto' mode with face recognition switched on either. Or 'portrait' scene mode. It's all there, use it.

 

[AceP]

Aberaeron wrote:

It is ironic [or something] that if a small sensor cheap point-and-shoot were used in 'auto' mode, both subjects would have been pin-sharp.

It would appear sharp because of the increase in depth of field from the small sensor but it would not actually be in focus.

To get both in focus using your kit would need a substantially stepped down aperture. F16 perhaps.

And that is about equivalent to what the small sensor would give you in DOF at f3.2. DPR just added a graph depicting equivalent apertures vs. format in their reviews.

 

[Mystery member]

Nice looking couple; perhaps they could have been closer together to fix the focus issue? They are engaged, after all. Girl looks thrilled, guy not so much; smile for the camera perhaps?

Have a better background and get rid of the upright behind the girl. Standing rather than sitting on that low wall would give more background options, allowing greater DoF.

 

[Aberaeron]

AceP wrote:

Aberaeron wrote:

It is ironic [or something] that if a small sensor cheap point-and-shoot were used in 'auto' mode, both subjects would have been pin-sharp.

It would appear sharp because of the increase in depth of field from the small sensor but it would not actually be in focus.

To get both in focus using your kit would need a substantially stepped down aperture. F16 perhaps.

And that is about equivalent to what the small sensor would give you in DOF at f3.2. DPR just added a graph depicting equivalent apertures vs. format in their reviews.

Firstly it could well be that both subjects would be in focus.

Second paragraph, it's late and I'm tired, but haven't you got that about face? Help someone!

Got a very long day ahead tomorrow with stressful business assurance inspection and a 300 mile drive afterwards, so I'll defer to others.

 

[AceP]

Aberaeron wrote:

AceP wrote:

Aberaeron wrote:

It is ironic [or something] that if a small sensor cheap point-and-shoot were used in 'auto' mode, both subjects would have been pin-sharp.

It would appear sharp because of the increase in depth of field from the small sensor but it would not actually be in focus.

To get both in focus using your kit would need a substantially stepped down aperture. F16 perhaps.

And that is about equivalent to what the small sensor would give you in DOF at f3.2. DPR just added a graph depicting equivalent apertures vs. format in their reviews.

Firstly it could well be that both subjects would be in focus.

Only if they are in the same plane as others have stated and not because of a difference in format

Second paragraph, it's late and I'm tired, but haven't you got that about face? Help someone!

I guess you are tired as I can't make any sense of what you just said.

Got a very long day ahead tomorrow with stressful business assurance inspection and a 300 mile drive afterwards, so I'll defer to others.

Well get some sleep and drive safely thereafter!

 

[dad_of_four]

Aberaeron wrote:

Absolutely nothing wrong with using 'auto' mode with face recognition switched on either. Or 'portrait' scene mode. It's all there, use it.

IIRC, Portrait mode specifically selects a larger aperture so as to get a smaller DOF so that the "face" pops out of the background.

Lacking any other photo training, the OP might have chosen Landscape mode so that he/she gets a larger DOF

 

[CLJphoto]

Thank you everyone for the great advice. One more question... I'm considering buying either the 24-70mm 2.8 nikon lens or the 70-200mm. Assuming I will be doing mostly portrait work like this which lens would be most useful for me. Currently I have the 85mm f1.8 50mm f1.8 and the 24-120 f4. I have the D800 body. Thanks in advance

 

[Mystery member]

CLJphoto wrote:

Thank you everyone for the great advice. One more question... I'm considering buying either the 24-70mm 2.8 nikon lens or the 70-200mm. Assuming I will be doing mostly portrait work like this which lens would be most useful for me. Currently I have the 85mm f1.8 50mm f1.8 and the 24-120 f4. I have the D800 body.

The traditional recommendation for portraits is somewhere around 85mm, so you already have that well under control; if pressed, you could probably get away with even the 50mm plus a bit of cropping.

Unless you are unhappy with the 24-120 f/4 (which already gives you a reasonably wide angle), I'd go for the 70-200mm to lengthen your options. And yes, you could use that for portraits as well.

I use the 50mm f/1.8 on my D3200 as a portrait lens; cropping already done!

Edit: Just noticed that the engagement ring is probably meant to be featured, and also needs to be considered in focussing. Subjects standing, closer together, higher f-stop and background further away should work. 85mm lens.

 

[Nates196]

quick question please, when you uploaded your photo as example how did you add image info/details when you hoover over image??

I am new to the site and photographer

thank in advance