help with group photos

htc8p · Apr 15, 2014

Hi everyone.

i bought a canon 100D but it seems like i have better results with my ixus 850is

i joined my 4 yo sons field trip. so there is always a class picture. some of the kids are out of focus while some are in focus. it is driving me crazy.

i am in manual mode and i use all the focus points (that light up in red)

what am i doing wrong?

thanks!

well i dont think i have problem with shutter speed. there was not enough light but i am using a speed light. i dont think it is subject movement because they were all still.

they are lined up in 3 rows.

could be depth of field because im using the kit lens(18-55mm). but then how come my kid would be clear while the kids around him (front, side, rear) would be out of focus? i notices that those children in the 9 AF points would be clear while those not in the AF points would be blurry

Braineack · Apr 15, 2014

You should probably do a bit of reading on the exposure triangle and then how aperture affects Depth of Field.

tirediron · Apr 15, 2014

It would help greatly if you could post one of the images, along with full EXIF data to help us diagnose the problem.

KmH · Apr 15, 2014

When the photo is taken the camera will have used only 1 of the many focus points, because it cannot focus at a variety of distances in a single photo.

Auto focus and depth-of-field have to be considered together.
Setting up AF requires making two settings selections - the AF mode and the AF Area mode.
The 1 point of focus the camera can use then sets how far from the camera the depth-of-field (DoF) is.

The depth-of-field is a plane that is parallel to the plane the image sensor is in.
If you angle the camera up from level and plumb, the plane of the DoF also gets angled such that the top of the plane of DoF is closer to you than the bottom of the plane of the DoF.

Understanding Camera Autofocus
Understanding Depth of Field in Photography

Designer · Apr 15, 2014

htc8p said:
well i dont think i have problem with shutter speed. there was not enough light but i am using a speed light. i dont think it is subject movement because they were all still.

How was the light? Did your speedlight illuminate the entire group?

When photographing people, you have to keep your shutter speed up to a minimum, say around 1/60 of a second even if the camera is supported by a tripod. For hand-held shots, your shutter speed should not exceed the reciprocal of the focal length of the lens. VR will help when hand-holding.

With three rows of people, even standing very close, the DOF needs to be around four feet (thick) to give acceptable sharpness on all their faces. If standing kind of "loose" the DOF might need to be more like 5 or 6 feet (thick). Use the DOF calculator to determine what aperture you need to produce the DOF that will be required.

As KmH wrote; if the camera is pointed upwards, it tilts the DOF (plane) the "wrong" way, that is; with the top out toward you, and the bottom in toward their feet. Ever see an old-timey picture of a photographer on a tall stepladder taking a group photo? It may have been partly to make sure all the faces were in the picture, but it also had the added advantage of tilting the DOF (plane) more in concert with the faces in ranks.

So, plugging rough some estimates into the DOF calculator, Online Depth of Field Calculator (using Canon 300D, I didn't see a 100D) and my own estimates, I get this:

Depth of field
Near limit	12.4 ft
Far limit	50.9 ft
Total	38.5 ft

So there is adequate DOF using f/16, 55mm lens.

Plug in your own values to see the actuals.

glun · Apr 16, 2014

The main reason I think is your depth of field. You need a higher f stop for the group and you don't need to have all 9 point focus in red before you take the shot (I know this is subjective to many photographers), but as long as the person closest to you is focused and you have a high enough f stop say f8 or f11, your focusing issue should be fixed. Of course the 3 rows aren't feet apart.

I also suggest you reading the above comments and links. Hope this helps!

JosephW · Apr 18, 2014

As others have said your DoF is way too shallow, you need a nice thick DoF with a high aperture, I'd say around f/11 or f/8, but you're gonna need to lower that shutter speed. Lower apertures means darker photos but also better sharpness too!

htc8p · Apr 19, 2014

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2 shots are not acceptable to me while i got one shot good which is a fluke. as of know i have no idea what the problem is so i dont know the solution. the front lower right people are clear while the upper left are blurry

what do you think?

htc8p · Apr 19, 2014

Braineack · Apr 19, 2014

looks like you focused on the pole.

Designer · Apr 19, 2014

I can't read the EXIF on these photographs. You see that the group is situated at an angle to your camera, so depending where your focus point was, and how deep was you depth of field was, you might be missing focus on quite a few of the subjects.

JerryLove · Apr 19, 2014

I agree that we could be more precise if we had the EXIF data (so we knew ISO and F values, letting us know if F should be increased). But I agree Braineack: You seem to have focused on the poll. If you were using AF with all the AF points selected: It's prone to choosing the closest object in the frame. (one down-side of Phase-focus is it can't really tell what an object is).

So. Three solutions to the "focus on the pole" problem. 1) Manually focus. 2) Set auto-focus to use an AF point over a kid in the middle row. 3) Set auto-focus to use only the center focus point. Put that focus point over a kid in the middle-center. Depress your trigger half way so AF kicks in. Recompose your shot and take it. (make sure you aren't on AI Servo focus mode)

or, of course, recompose so there's no pole to focus on

cynicaster · Apr 21, 2014

IMO, it makes no sense whatsoever to use multiple focus points on a shot like this. I don’t see a benefit to manual focus in this situation either, unless you are intent on making things more difficult than they need to be.

Just select a single focus point and force the focus at an appropriate spot, thereby preventing the camera from making an incorrect decision that you should be making yourself.

As a side note, keep in mind that depth of field extends both fore and aft of the focus plane, meaning that if you set focus on the face of the closest kid, you’re wasting the portion of the available depth of field that sits in front of that kid. At these distances and the focal lengths that are appropriate, the DoF split is roughly 1 part to 2 parts in front of and behind the focus plane, respectively.

You probably don’t even need to be concerned with such academic minutiae though, because here, if you were shooting at, say, 35mm focal length, f/8, at a distance of 15 or so feet on a APS-C camera (like yours), you’ve got about 25 feet of DoF to work with, so focusing on any kid in the first or second row would probably work just fine.

If you’re shooting with the common 18-55mm kit lens, it’s worth mentioning that it sharpens up considerably when set to 35mm and f/8-f/11 (at least, my copy does), so you probably want to be in that range anyway, if conditions permit.

ryanita · May 2, 2014

In my opinion..you can using

..If you frame the shot so that the main subject is in the selected focus point, focus, and then change the composition while keeping the shutter-release button pressed halfway to lock focus, you can create compositions in which the main subject is not in a focus point but is nevertheless in focus.

Seventen · May 4, 2014

It looks like focus was on the pole, but also could it be camera shake some of the children actually look stretched rather than blurry. Putting exif data up would be a big help.