Aperture/F-stop and Focus

Aperture (F-stop) and Focus
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September 8, 2009
Tonight we took our cameras through all of the aperture levels available in our cameras (f-stop is another term that refers to this). We put the SLR dial on "A," "AP" or "AV", then turned the dial to get the lowest aperture number, then dialed it through to the largest. We had a demonstration with funnels and 1/2 cup salt. With the large hole (small aperture number, like 4), the salt went through quickly. With the small hole (aperture 20) it took longer but the added time lets the lens capture more detail and depth. Several with point-n-shoot cameras did this exercise by taking a photo with the same focusing point in the icon mode with a mountain and then with a face or flower. This gave them a small opening (large aperture number - 17) or a large opening (small aperture number - 4), show the same effect.

We then worked on locking our focus, then composing our picture. Some SLR cameras would not lock focus because they were not in the single shot focusing mode. Once we changed the focusing mode to single shot, the focus could be locked. Some point-n-shoot cameras would not allow a center focus or lock (at least, from what we could find in the books as we were looking).
Face finder is a focusing mode that focuses on several faces or points. Center focus allows the photographer to choose what is focused and what is not.
We used tripods or steady surfaces, releasing the shutter with the timer to avoid camera shake (this results in blurry pictures because the camera moved when the button was pushed). We tried shots from different angles and different points of view like birds eye view (shooting down from above), worms eye view (from the ground up), and taking shots on an angle.
If you weren't able to join us, here's what was on our task sheet and homework assignment:
· Take one shot of same object using all aperture values. Use flat surface and timer to release shutter. (Point-n-shoot, take a shot in landscape mode-mountains, and one shot in flower or face mode).
· Practice locking your focus. Take 2 shots of same composition, but change focusing point
· Shoot from bird’s eye view
· Shoot from worm’s eye view
· Shoot at an angle
Homework:
Post 2 shots of AV (aperture value), smallest and largest number.
Post 2 shots of focus lock, either a pair, or 2 favorites that are different.
Next week we are focusing on time values--how to freeze motion and how to show movement. We'll meet in the Kroger parking lot, close to the back of the gas station to carpool over (this is a neighborhood and we don't want to bombard them with too many cars). If anyone emails me beforehand, I can be there at 6:00 to answer any specific questions. We'll meet at 6:25, fill vans/cars, and drive over. If you have one, bring a tripod. If you don't, we can stead your camera on a rock or bench.