Group shots and focus

Greyhound Rick · December 25, 2008

Other than shooting racing greyhounds I feel like Im brand new to photography so Im going to ask some very basic questions and Im sure I will learn a lot from you folks!

I took some candid shots tonight at our house of some family and just put my flash on my D3 and started walking around and shooting. Here was my set up:

SB-800 set to TTL-BL
SS 1/200
ISO 400
Aperture between 7-13
Single servo
Single shot shutter mode
Single point focus
Active D Lighting normal
Matrix metering
Focus only shutter release
RAW
M exposure
Picture Control standard with sharpness set to "5"

While shooting my images I noticed something right off the bat that I really havent dealt with before. When I was shooting say, 4 or 5 people sitting together at the table or on the couch, the person that I focused on was very sharp. Most of the time the person next to them was sharp also, but as I looked at others I noticed the focus was not spot on.

I used my D3, 70-200mm lens with VR on. I was handholding the camera.

I understand that DOF can be calculated but honestly, I was expecting in a group shot that everyone would be in focus at an aperture of 7-13, however that was not the case in some instances.

I would describe the focus as OK with some of the people not focused on with the focal point, but not spot on dead, solid perfect.

Is this normal or is my technique causing me to miss something here?I would assume that since the subject Im aimed at is focused very well that maybe i cant expect everyone in the shot to be perfectly focused as well.

Also, would going to 21 pt., or 51pt. be a better way to shoot muliple subjects especially while walking around?

Thanks for your help and guidance. I feel like Im starting over!!

take care,

Rick

Greyhound Rick · December 25, 2008

Im sorry to add this after the fact....but I just wanted to clarify that the shots that I dont consider to be "spot on" are just that, not spot on where you can magnify them quite a bit and they still look super sharp.

Is super sharp, spot on crystal clear focus attainable for EVERYONE in the group or is that setting the expectations too high?

thanks and sorry for the extra post,

Rick

Greyhound Rick · December 25, 2008

Did a little reading on the subject and will try the following to increase DOF and COF:

1. Close down the aperture to f/13+
2. Increase distance from camera to subject
3. Shorten focal length of lens
4. Increase ISO to 500-600 or so to compensate for less light from tighter aperture or use more flash power.

Does this sound like a good approach?

thanks,

Rick

jfriend · December 26, 2008

Greyhound Rick wrote:

Did a little reading on the subject and will try the following to increase DOF and COF:

1. Close down the aperture to f/13+
2. Increase distance from camera to subject
3. Shorten focal length of lens
4. Increase ISO to 500-600 or so to compensate for less light from tighter aperture or use more flash power.

Does this sound like a good approach?

thanks,

Rick

Depth of field is purely a geometry problem. With a given camera sensor, focal length, aperture and subject distance, you get a certain depth of field.

You have indeed read about how to get more depth of field, but there are also some downsides to going to f/13 with a flash as that aperture is cutting out so much light that the flash is going to have to go to high power. Not only will this limit the range the flash can reach, but it will also severely cut down the amount of ambient light that gets to the sensor from your background. Chances are your shots will have a very dark background such that only your subject will be properly illuminated.

If you could post some of the shots that don't seem to have the depth of field you want (with EXIF info), we might be able to offer some additional suggestions.

pathfinder · December 26, 2008

A 70-200mm lens is a long lens to use indoors with a crop camera, and will allow a fairly shallow DOF, as you are experiencing.

I agree that f13 is going to not be ideal as too small and aperture, and too much diffraction even tho you will have more DOF.

Try shooting at 50 to 80 mm at f5.6-f11 and see if you aren't happier with your DOF

You may have too high an expectation also, as a monitor allows inspection of images in a different manner form looking at prints.

Are you shooting in RAW? Are you performing capture sharpening in your RAW converter, or is your camera applying sharpening to your images? Files come out of a DSLR fairly soft and low contrast unless the proper settings are chosen in the camera as well.

Post a few frames to let the viewers here see what you are describing and see if they agree.

Greyhound Rick · December 26, 2008

Thanks VERY much jfriend and pathfinder!! Your comments are very helpful and most appreciated.

Right now I have 2 lenses. An 85mm f/1.4 and 70-200 f/2.8 VR. My camera bodies are D3/D300. Im just getting started in portraits and am not good at all at doing them because I really dont know what Im doing. Lots of trial and error!!

I will post some group shots soon, but for now here are a couple of our daughters I took yesterday on Christmas. Im not happy with the lack of light in their eyes and in the second photo Valerie's long side is blown out too much, but considering Ive only done this a couple of times I guess they are OK.

Im fanatical about focus (to a fault), but thats just me. If my shots arent in focus Im unhappy. So, with that said, please let me know what you think of my focus and how I can improve.

My settings are around f/11, ISO 400, single point focus, "S" servo. I use the VR when hand holding the 70-200 and its turned off when on a tripod. My subjects tend to move a bit so Im wondering if "C" servo with AF-Dynamic might be better with 9, 21 or 51 pt. selected. I use the Picture Controls and usually set the sharpness to "5-7" on a scale of 1-9. The default is "3" which I believe is too soft, but thats just me.

Please let me know if there is any other data I can give you to better have you evaluate this for me and most importantly....THANK YOU for taking your valuable time to help this noob!

Im pretty good at shooting racing greyhounds, but this is a whole new world for me and Im out of my comfort zone!!

many thanks,

Rick

Valerie

Valerie and Natalie

thanks again!!!

jfriend · December 26, 2008

Greyhound Rick wrote:

Thanks VERY much jfriend and pathfinder!! Your comments are very helpful and most appreciated.

Right now I have 2 lenses. An 85mm f/1.4 and 70-200 f/2.8 VR. My camera bodies are D3/D300. Im just getting started in portraits and am not good at all at doing them because I really dont know what Im doing. Lots of trial and error!!

I will post some group shots soon, but for now here are a couple of our daughters I took yesterday on Christmas. Im not happy with the lack of light in their eyes and in the second photo Valerie's long side is blown out too much, but considering Ive only done this a couple of times I guess they are OK.

Im fanatical about focus (to a fault), but thats just me. If my shots arent in focus Im unhappy. So, with that said, please let me know what you think of my focus and how I can improve.

My settings are around f/11, ISO 400, single point focus, "S" servo. I use the VR when hand holding the 70-200 and its turned off when on a tripod. My subjects tend to move a bit so Im wondering if "C" servo with AF-Dynamic might be better with 9, 21 or 51 pt. selected. I use the Picture Controls and usually set the sharpness to "5-7" on a scale of 1-9. The default is "3" which I believe is too soft, but thats just me.

Please let me know if there is any other data I can give you to better have you evaluate this for me and most importantly....THANK YOU for taking your valuable time to help this noob!

Im pretty good at shooting racing greyhounds, but this is a whole new world for me and Im out of my comfort zone!!

many thanks,

Rick

thanks again!!!

For folks wanting to look at the full sizes to really see the focus, they are:

http://www.flickr.com/photos/14914549@N08/3137597937/sizes/o/
http://www.flickr.com/photos/14914549@N08/3138423660/sizes/o/

pathfinder · December 27, 2008

They certainly seem sharp and acceptable to my eye.

The catchlights in their eyes are small - a larger apparent light source, a little lower perhaps, might give larger catchlights in their eyes. This looks almost like a point source, rather than a large softbox or windowlight.

jfriend · December 27, 2008

First off, this is not bad at all. My guess is that you could make a pretty good sized print from it and it would look very nice. But, if you want to analyze what you've got here, I'll offer my thoughts.

These are taken at 1/250th, f/11 and 85mm and 75mm with flash on a D300. Assuming the images are not cropped, it looks to me like you were about 10 feet away when you took it.

Using a DOF calculator set for this camera, focal length lens and distance, you could expect a DOF of about 2.43 feet.

That does not mean that the image will have perfect sharpness throughout that whole depth of field, just that it should be acceptably sharp in that range (which is a subjective standard). This particular depth of field calculate uses a desired circle of confusion (how sharp it must be) of 0.02mm, but what this number needs to be depends upon how much the image will be enlarged and the viewing distance from the print. It needs to be smaller for bigger enlargements. Or, it can be larger if the viewing distance from the print is not close.

Now, when I look at the image that has both of the girls in it, I think I can see the limits of the DOF on the left girl. Her black sleeve and forward arm is not quite as sharp as it could be - I can't tell whether this is what happens with this lens in the corner or whether we're just starting to see the edge of the DOF. On the other hand, pretty much everything we can see of the girl in green is sharp. If the primary focus point was on the shirt of the girl in the green (which would be a worst case here), we should have DOF about 1 foot in front of that for sharp focus. That would probably just barely get us to the left girl's black sleeve. Add to that just a little loss of sharpness in the corners and we could have an explanation for the arm/sleeve.

What I don't' quite understand is the face of the girl in black just doesn't seem quite as sharp as the face of the girl in green. Yet, it doesn't seem like one is more than a foot further away from the camera than the other so they should both be within the DOF for these conditions. It is possible that part of this is because her face is overexposed and thus we have a loss of some visible detail in the highlights. A big component of perceived sharpness if how much detail we feel we can see so this overexposure can influence our perception of sharpness.

If I really had to guess here, I'd say that the center of focus is a little behind the face of the girl in green. I don't know if you focused it there somehow, locked focus and then moved a bit causing it to go there or if your camera/lens combo just back-focuses a bit.

You didn't say what focus technique you used, but if you just framed this exact show and used the center sensor, the focus sensor would see the space right between the two girls which would include a piece of the background and the furthest back part of their hair. If that's what it picked to lock focus on, that could also explain all the observations we see. On the other hand, if you locked focus on a specific part of one of the girls, then we'd have to look for a different explanation.

Greyhound Rick · December 27, 2008

pathfinder wrote:

They certainly seem sharp and acceptable to my eye.

The catchlights in their eyes are small - a larger apparent light source, a little lower perhaps, might give larger catchlights in their eyes. This looks almost like a point source, rather than a large softbox or windowlight.

thank you pathfinder (by the way.....We own two pathfinders!! a '94 & a '97, love them, weve had a total of 5!!)

yes, I need to get more light in the right places! I think youre right on with your assessment that a larger light source may be in order. What would you recommend?

thanks again,

Rick

Greyhound Rick · December 27, 2008

jfriend,

thank you very much for your time and expertise!

Yes, you are right. I was about 10' away from my daughters when i shot these!

The focus point of the single girl (Valerie) was her left eye. The focus point of the dual shot was Valerie's (girl on the left) right eye.

I understand how the overexposure of Val in the image with both girls could have caused it to look OOF. That makes sense.

I would really like to improve my overall focus as focus is VERY important to me and I would really appreciate your continued recommondations.

thank you very much again, for your help.

my best,

Rick

jfriend · December 27, 2008

Greyhound Rick wrote:

jfriend,

thank you very much for your time and expertise!

Yes, you are right. I was about 10' away from my daughters when i shot these!

The focus point of the single girl (Valerie) was her left eye. The focus point of the dual shot was Valerie's (girl on the left) right eye.

I understand how the overexposure of Val in the image with both girls could have caused it to look OOF. That makes sense.

I would really like to improve my overall focus as focus is VERY important to me and I would really appreciate your continued recommondations.

thank you very much again, for your help.

my best,

Rick

It interesting that you focused on Val, but the other girl looks sharper. My only plausible explanations are:

You moved the camera a bit towards the girls when reframing after focusing.
You didn't actually lock focus where you thought you did.
Your lens/camera is back-focusing some.
Your 70-200 lens is soft on one side at this distance.

Items 3 and 4 can be ruled in or out with some focus tests.

If you are looking for critical focus on multiple people at once, you should think about the following:

Get the heads of the different folks as close to the same plane as you can so they are all the same distance away from the camera. Sometimes this means adjusting the pose. Sometimes this means adjusting your position. Sometimes both.
At close distances like this, you have a little more DOF behind the focus point than in front, so it is a good idea to focus on something like the face rather than a body (which it sounds like you did).
Learn how much DOF you have to play with at a couple apertures for a couple poses. In a fairly neat outcome of the math, you get about the same depth of field if you have the same magnification of your subject regardless of focal length. At the same aperture and with the same camera, a 35mm lens that is close enough to take a head shot will generate about the same subject depth of field as a 200mm lens with the same head shot composition. This means you can learn what DOF you can expect at f/2.8, 5.6 and 11 for a single head, two heads or four heads and it will be the same regardless of focal length. Obviously a shorter focal length will position you closer for the same shot, but the depth of field comes out about the same. Here's you've got two heads in the shot, f/11 and you should have about two feet of DOF. At f/5.6, about 15". At f/2.8, about 8".
Look at the expected performance characteristics of your lens so that you know it's sweet spots. If you check out slrgear's bench tests of the 70-200 (http://www.slrgear.com/reviews/showproduct.php/product/134/cat/13), it surprisingly has a focus sweet spot at 70mm at about f/4 and actually loses edge performance when you stop it down. Even at 200m, it's better at f/8 than f/11.
If you haven't already, perform focus calibration on your D300, 70-200 combination to get the maximum out of the two.

Greyhound Rick · December 27, 2008

thank you John! Fantastic information.

Ive focus tested my lens and also had it checked by my local camera shop so I think its fine.

I will use your tips to try to improve my focus. Valerie has a tendency to move during these shots so I think that may have caused the better focus on Natalie.

Do you think using "C" servo and possibly 9,21 or 51pt dynamic AF might be worth a try? (especially with Val!!)

thank you,

Rick

jfriend · December 27, 2008

Greyhound Rick wrote:

thank you John! Fantastic information.

Ive focus tested my lens and also had it checked by my local camera shop so I think its fine.

I will use your tips to try to improve my focus. Valerie has a tendency to move during these shots so I think that may have caused the better focus on Natalie.

Do you think using "C" servo and possibly 9,21 or 51pt dynamic AF might be worth a try? (especially with Val!!)

thank you,

Rick

You should not have to use AF-C focusing. If she's moving a few inches that shouldn't be a problem. If she's moving a foot, then she needs to be more still than that for a posed shot.

You should stick with a single sensor. With dynamic, you can't be assured what the camera will focus on and you know exactly what you want it to focus on. I would not use dynamic for this circumstance.

You could try setting it up so you don't have to reframe by selecting the focus sensor that is on her eyes and then do a half-press, see focus lock and then shoot with a lot less delay between focus and shot. When I shoot people though, I usually lock focus, then wait until I get the expressions I want before shooting which necessarily involves a delay sometimes.

When you focus tested it, did you specifically test it at 80mm where you're shooting these? It is common for people to focus test the 70-200 at 200, but not at the shorter end. It can be different.

Greyhound Rick · December 27, 2008

Great input John. thanks.

I tested the lens at somewhere around mid range, but cant remember exactly which focal length.

Will keep it in "S" servo and single point with focus point over one of her eyes and will press the SRB quickly after focus is achieved.

Will also try focus lock. Ive used that sometimes when shooting the greyhounds and feel comfortable doing that.

Rick

Group shots and focus

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