Hi, for night shooting, to get a sharp image, is it better to set long shutter (20sec), high aperture (F11) THAN short shutter (2sec), low aperture (F3.5) ???
I also suggested "Understanding Exposure" as the best book to start with, you should understand more about aperture, shutter speed, ISO and how this combination affect your image.
In the mean time I tried to reply your question above.
1. For landscape you in general should use high f, usually I use 5.6 to 11. The reason is for landscape picture you want everything in the scene to be as sharp as possible, and high f gives you large Depth of Field. Should avoid using higher f than f11 as for most lens diffraction start kicking in after f11, the picture taken by your lens is actually less sharp.
2. Long or short shutter does not decide the sharpness of your picture if you mount your camera on a sturdy tripod. But for landscape with water in the scene, longer shutter makes the water look kind of soft and dreamy, so it is a good practice here.
3. Most people who just start taking landscape make a mistake in focusing to infinity. Try to read about hyper focus distance and focus correctly.
Here is what I will do for the Helix Bridge scene.
Mount camera on tripod, and compose the picture
Set your lens to 18mm, f to 11, adjust ISO such that shutter speed 15 sec for a good exposure.
Set focus distance to around 2.3meter(which will provide sharpness from 1.5m to infinity)
Shoot
This settings should give a much sharper image
Just my 2 cent.
Would welcome any experienced bro to drop in and give some hints to my workflow, I'm still new and is here to learn too