Did a few birthday pics for a friend at the weekend, very pleased with the majority, apart from a couple taken of a family....
Shot at 15th at 5.6 ISO 400 bounced flash Now 5.6 is normally perfectly adequate for small medium groups around tables however I am suprised at the two males in the picture are so far out of focus especially the young lad, compared with the two girls, other small groups with greater depths than this one shot with same settings are perfectly fine. but very suprised and somewhat baffled by these. focus point was the face of the young lady.
If you shot at 40 mm F5.6 and were about 2 m away, then 500 mm behind the focus point should have been sharp
If you shot at 100 mm F5.6 and were about 3 m away, then 160 mm behind focus point would have been sharp
You need to look at the exif data to check what actual focal length you shot at and how close you are to the subject will make a difference.
I can only think of a couple of reasons from the info you gave me 1) Focus error - the point was actually in front of the nearest person so they still were in focus but back two dropped out of the zone of sharpness 2) You actually shot these with the 100 mm which would have meant the zone of sharpness from the focus point was only 160 mm backwards and the two males look further back