MODERATOR NOTE: I split this off into a new thread so that Sue's image and my response wouldn't be split by a page break.
Sue,
Thank you for participating. The reason for the assignment was to help people learn, so it doesn't really matter if you are late as long as we all learn something. I've posted the EXIF information for your image below, since that helps me analyze the image and maybe offer a suggestion or two.
EXIF:
Camera: Nikon D300
Exposure: 1/60"
Aperture: f18
Exposure Mode: Manual
ISO: 200
Exposure comp: +.7 EV
Metering: Matrix
Focal lenght: 300mm
White Balance: Manual
effective FL: 450mm
First, nice job isolating the subject from the background. One thing you will notice with these types of images is that if the background is partially in focus it can really distract from the image. Since depth of field is very limited at these focusing distances, which makes it almost impossible to have both the foreground and background in focus, it is usually much more effective to have a smooth out of focus background than it is to have one that is partially in focus. The best way to do this is to try to put your subject in front of a background that is far enough away that it renders as a smooth out of focus background with no distracting detail. The best way to evaluate the background is by using the depth of field preview or the "live view" option on the newer cameras.
When we talked about this image you expressed disappointment that the bee was blurry. I think the reason for this is the very limited depth of field available at these focal lengths and close focusing distances. It looks like your focus point was on the very front of the flower. Those parts of the image are sharp; however, the bee appears to be slightly outside the depth of field available at this focal length and focusing distance.
I played around with a depth of field calculator for a 300mm lens used on a camera with an APS-C size sensor focused at about 12 inches, and the depth of field is less than an inch. Remember that depth of field is affected by three variables, aperture, focal length and focus distance. Using a longer focal length lens (at the same focus distance) or focusing closer (using the same focal length lens) will drastically reduce your depth of field.
Many people would have been tempted to use a smaller aperture to try to get more depth of field. However, as we discussed on the phone, using an aperture smaller than f11 on a sensor with small pixels like the D300 is counterproductive since the image starts suffering from diffraction effects. I would hesitate to use an aperture much smaller than about f13 or so unless you absolutely have to in order to get parts of the image in focus. If you do use an aperture smaller than f11, you will have to compensate in post processing by applying more sharpening to the image.
In this case, I think you would have been happier with the image if you had focused on the bee instead of the flower. The front parts of the flower would have been slightly out of focus, but those parts of the flower that were in the same focus plane as the bee would have been in sharp focus. I think that might have worked better for this image.
Since we're making recommendations, I would probably have bumped up the ISO for this image as well. That would have given you a faster shutter speed, and reduced the chances of motion blur from camera or subject motion. You could probably have bumped the ISO up to 800 and still not seen objectionable noise in the image. That would have given you a shutter speed of 1/250", which would have given you a much better chance of capturing the image without motion blur.
Thanks again for letting us use this image as an example for discussing some of the factors that come into play when trying to "isolate" a subject from the background.
Keith
