Originally Posted by
Travis
The first image (person in shade with blinds)
This was shot in shutter priority mode. You selected a speed of 1/80 and the camera had to correspond with an aperture that would get you a correctly exposed image. Only problem is you don't have a wide enough aperture to shoot 1/80 with the ambient light in this room.
Your camera elected to use the widest aperture available (in this case F4). This is why the image is under exposed.
To answer the question about sharpness for this image. Lenses are never as sharp at their widest apertures. They are sharpest a stop or two down from widest. This lens is most likely sharpest at f7-f11.
Was you intention for this shot to be a silhouette? or did you want the persons face properly exposed? if it's a silhouette I wouldn't worry so much about sharpness, if it's supposed to be exposed and razor sharp than you can -
A - Use flash to increase the amount of light in the room and increase the aperture to F7
or
B - Increase the ISO (which will bring some noise) and increase aperture.
This is a sharpness to signal to noise ratio trade off.
Flash and Increased aperture would be my choice
The 2nd picture (kitty)
This looks pretty sharp to me. In this case you kept the shutter at 1/80 and shot it at 100mm. The iso was increased to 1200 but the camera is handling it well. Mostly because the image is correctly exposed. The aperture was F4.5 is is the widest for this lens at this range (100mm).
If you are referring to the out of focus areas under kittys chin this is the effect of depth of field when shooting both at 100mm and a relatively wide 4.5 aperture. This effect is often desirable. However if you wanted all of kitty in complete sharp focus you would have to
A - Stop the aperture down to F7. This will force you to either increase your ISO (which will increase the noise) or use a slower shutter speed (which may introduce motion blur). You can't really move the shutter speed much further down because your're shooting 100mm. This would suggest 1/100 for the appropriate shutter speed. You are already pushing it at 1/80 (unless you have IS lenses in which case you might be able to go a touch slower but if your subject moves it's over).
B - Use flash and stop down to F7. Decrease the ISO back down to base.