The other day I was trying to take a picture of all my family spread out. When I put the image onto the big screen, the people in the middle were in focus and those around the edge weren't in focus. How can I make sure everyone is in focus?
3Does How do I keep both the background and foreground in the image in focus at the same time? tell you what you need to know?– mattdmJan 2, 2017 at 21:15
Were the people at the edges of your images the same distance from the camera as the ones in the center? How spread out were people?– mattdmJan 2, 2017 at 21:16
4It might or might not be a focus issue. Some lenses are just softer at the edges than the center. Can you post an example and tell us what lens, camera, and settings (shutter time, aperture, etc.) you used?– Michael CJan 2, 2017 at 22:36
Possible duplicate of outdoor group photo - depth of field, other concerns?– Michael CJan 3, 2017 at 8:56
A few suggestions:
Use a small aperture. An aperture with a large f-number (eg. f/11 or f/16) has a small opening. ('f' means 'focal length', so 'f/16' means the focal length divided by 16, or 1/16th of the focal length, where as f/2 is one half of the focal length, which is much larger than 1/16th - which is why f/16 is smaller than f/2). A small aperture has a large depth of field making it more likely to keep everyone in focus.
When framing your shot, don't put people near the edge of the frame. Rather, take the shot expecting to crop it down to the people. This will keep your subject matter near the centre of your image where your lens is sharpest. However, you will lose resolution. Depending on the camera's sensor size the final product may not be of the quality you need.
Research your lens on the web to find out at which aperture it shoots sharpest, and use that aperture.
@mattdm Most lens designs attempt that. What they actually achieve is often a wavy shape that undulates back and forth and can be either closer or further at the edge than at the center (And that is when they are properly aligned). lensrentals.com/blog/2016/11/… Jan 3, 2017 at 5:12
@mattdm - I stand corrected, and this is evident by examining any image taken with a shallow depth of field: the portion in focus runs linearly across the image, not in a curve. I have removed #1. Jan 3, 2017 at 6:34
@MichaelClark "as close as possible"– mattdmJan 3, 2017 at 9:47
Are you talking side-to-side edges, or front-to-back? As Michael Clark says, some lenses are sharp in the center and softer at the edges. Excluding special effect lenses, this is undesirable, and edge-to-edge sharpness is the ideal. Better quality lenses have better edge-to-edge focus.
If you have issues with images that are softer at the edges than in the center at the same focus distance, you might need to invest in a better quality lens.
Front-to-back focus differences are a major consideration. If the people on the edge of the frame were closer to/further from the camera, they might be outside of the depth of field for your camera settings.
Try positioning your subjects so as to limit the front-to-back distance between the closest and furthest person. Ideally, put everybody in a single row.
Also use the smallest aperture you can. There are focus charts that will tell you the depth of field for your lens for a given aperture and focal length. You'll also want to take test shots with the settings you plan to use in a photo shoot and review the results for acceptable sharpness.
Use f/11, bring a big flash, and don't pixel peep.
f/11 will have a deeper depth of field which means you can have people behind each other and both rows will remain in focus. The big flash will help you keep your ISO and shutter speed down. Despite these steps, if you zoom into the image to the pixel level, you will still find some differences in sharpness. Realize that's inevitable with people are spread out.