FOCAL LENGTH - LENSES - WORKSHOP

I have a Canon Rebel t3 and I'm shooting with a Canon EF-S 18-55mm lens.

1/125 sec at f/5.6, ISO 800 (18mm)
More distortion in the background as well as on the object itself.

1/125 sec at f5.6, ISO 800 (55mm)
Less background, less distortion.

1/125 sec at f5.6, ISO 800 (35mm)
The image looks more flat and we see very little of the background compared to the two others.

1/50 sec at f/5.6, ISO 400 (55mm)
The face of the model looks more pleasing. The image looks more flat. This would be perfect for a portrait as it isolates the subject from any context.

1/50 sec at f/5.6, ISO 400 (35mm)
More context (background)

1/50 sec at f/5.6, ISO 400 (18mm)
The background takes more place than the subject. The image and the facial features get more distorted.

1/100 sec at f5.6, ISO 1600 (55mm)
At a higher focal length, with the same aperture, the DOF increases.

1/100 sec at f5.6, ISO 1600 (35mm)

1/100 sec at f5.6, ISO 1600 (18mm)
More context as the background is more in focus then the last two.

1/320 sec at f/4.0, ISO 100 (18mm)
The image is distorted and not as its sharpest.There's also more blur and vignette at this focal length.

1/80 sec at f/8.0, ISO 100 (18mm)
From all the 18mm focal length photos, this one is the sharpest.

1/40 sec at f/16, ISO 200 (18mm)
Not bad but not the sharpest. Less blur and vignette as we go higher with the focal length.

1/80 sec at f/8.0, ISO 100 (35mm)
f/8.0 seems to be the sharpest. This one is probably the sharpest of all. Still a little bit of distortion.

1/50 sec at f/16, ISO 200 (35mm)

1/60 sec at f/8.0, ISO 100 (55mm)
No distortion, the shapes actually look like they're supposed to.

1/60 sec at f/11, ISO 200 (55mm)

1/60 sec at f/22, ISO 800 (55mm)

Overall, for my 18-55mm lens, what seems to be the sharpest aperture is f/8.0 and the sharpest focal length seems to be 35mm (middle).