KMarcell Loc: Houston, TX

Every time I use my wide angle lens to take larger group photos the people in the middle are sharp while the people on the end are really blurry. What can I do to fix this?

amehta Loc: Boston

The distance from your camera to the people in the middle is different than the distance from the camera to the people on the edges. If you arrange the group in an arc, the distances will be closer to the same.

Flyerace Loc: Mt Pleasant, WI

Perhaps try to have a deeper depth of field by shooting at a higher f stop. Depth of field can be as shallow as a few inches when the f stop is at the lowest levels. A slightly less wide lens might also solve the problem. I hope this helps. (I've experienced the same type of problem in the past and this helped fix it.)

Nikonian72 Loc: Chico CA

Exactly correct. All standard lenses have a curved Field-of-Capture. A small aperture provides a deep DoF, which can cover that characteristic, but arranging your subject to emulate your lens' curved field works the best.

lighthouse Loc: No Fixed Abode

What lens are you using?
On what camera?

mcveed Loc: Kelowna, British Columbia (between trips)

I suspect you are too close to the people. Wide angle lenses have an apparent deep depth of field. Post an example and store the original and you'll get more focused help.

Pablo8 Loc: Nottingham UK.

With a wide-angle lens, and an experienced photographer using it, I would suspect the lens. Perhaps if you indicated what lens..aperture used... and camera, more help would be forthcoming. Even a group of 10/20 in two rows, I tend to curve the line. Always looks more pleasing to the eye than regimented straight lines.

Pablo8 Loc: Nottingham UK.

[quote=Flyerace Depth of field can be as shallow as a few inches when the f stop is at the lowest levels. )[/quote]
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At a distance from camera to subject of a large group, DOF will be more than a few inches, even on an f/2.0 wide angle lens. Close-ups/macro, I would agree on the few inches DOF, even fractions of an inch, but not at group shooting distance.

lighthouse Loc: No Fixed Abode

What lens are you using?
On what camera?

jerryc41 Loc: Catskill Mts of NY

Aside from aperture and distance, the quality of the lens can affect sharpness at the edges, something that's easy to achieve in a lens.

rocketride Loc: Upstate NY

Actually most ordinary photographic lenses are corrected to image a flat plane (not a concave surface) onto another flat plane (the film or chip). Fisheye lenses are the most common exception to this. These do, deliberately, project from a concave "bowl"-shaped surface onto a plane. They have to, to be able to cover 180+ degrees.

Most lenses do not image as sharply towards the outer edges (and especially the corners) as they do at the center of the frame. Stopping down moderately should help this, as well as increasing the depth-of-field you're working with. Most lenses have a best compromise aperture at around f/8 and f/11.

Nikonian72 Loc: Chico CA

This is an incorrect statement.
Macro lenses are known as 'flat-field lenses' because they are designed to capture a flat field, corner to corner. Nearly all other prime, and all zoom lenses, actually focus at an equal distance from front lens element, in an arc. All optical lenses are designed to project to a flat sensor or flat film.
http://photo.stackexchange.com/questions/29775/what-does-flat-field-focus-mean

"You might be wondering if the lens(es) you use have field curvature. Before you start your search, you should know that every single lens has field curvature – some stronger than others. While modern optical designs take field curvature into consideration and have specific elements within the optical design to reduce it, most lenses still suffer from it. In fact, even many expensive professional lenses from well-known brands (Nikon, Canon, Zeiss, Leica, etc) have very pronounced field curvature." per http://photographylife.com/what-is-field-curvature

romanticf16 Loc: Commerce Twp, MI

It also helps to focus on a middle row when photographing a group of people- the "rule" is to focus 1/3 into the group. Your depth of field will then insure sharpness of the front and rear rows if you are sufficiently stopped down.

rocketride Loc: Upstate NY

If what you and they say is true, why can I take my 6D with my 50mm f/1.4 non-macro lens, set them up on a tripod perpendicular to a perfectly flat brick wall, snap off a shot with the lens wide open, and have sharp brickwork all across my frame? (Well, it gets a little fuzzy at the corners, but that's mainly coma and lateral color, not field curvature.)

If you map a curved surface to a flat surface or to a different curved surface that is not conjugate to the original curved surface, you will get rectilinear distortion.

The majority of modern camera lenses don't have perfect correction for field curvature, just as they don't usually have perfect correction for any of the aberrations. What designers tend to aim for with field curvature correction is to balance different polynomial orders of the aberration so that they cancel each other out over the lens' useful field, which renders the field acceptably flat in that area- the cost is that once you get farther from the optical axis than that, the field curves away from the nominal plane much faster than that of a simple lens.

Picture a simple lens. If you focus it on a flat, distant object, it will form an image whose best focus (as you get away from the optical axis) curves towards the subject like a simple round-bottomed bowl, concave towards the subject and lens. A well corrected complex lens will have a focal surface that is almost dead flat (it will undulate a little) up to a point. After that point, it will curve away much more steeply. Think more like a flat-bottomed stewpot whose sides flare out a bit instead of being quite vertical.

Field curvature is especially critical with macro lenses, so designers use extra elements to provide a more optimal mix of orders of field curvature in order to hammer the focal surface flatter. For lenses that are expected to focus over large distance ranges, floating elements have become the norm. This allows more degrees of freedom in correcting aberrations.

The point is that nobody is designing ordinary (non-fisheye) photographic lenses to focus a bowl-shaped surface onto a flat film/sensor plane. It would lead to objectionable amounts of rectilinear distortion. On the other hand, not many designers of non-macro lenses are nailing field curvature down so the surface is dead flat. The residual zonal defocus that undulations in the focal surface produces is one of the easier aberrations to hide. In a well-designed lens, it hides in the depth of field either wide-open or stopped down just a little bit.

Unless you are an optical designer, I probably know more about this than you do.

Nikonian72 Loc: Chico CA

So, your argument is that you are right (despite your own cited evidence to the contrary), and the rest of the world is wrong. Got it.