How sharp of an image should I expect at night?

Question

I'm a beginner with my first camera (sony nex6 mirrorless). I was trying my first few night shots Using the kit lens but I wasn't able to find a way to take sharp images. I've done the following:

1. Used a tripod
2. Turned off stabilization
3. Remote shutter release
4. Taken at ISO100
5. I'm on stable ground unless the high rise building itself is shaking
6. Tried taking it at f/8 and f/5.6. It's around the same except just darker.

I guess two questions:

• Am I using taking the photo correctly (exposure etc)?
• What kind of quality should I be expecting from this set of gear?

Sample image below, full size image here (ISO100 f/5.6 20s):

Answer 1

Your foreground is not at all close in any real sense of the word "close", and it is sharp. Your middle ground isn't exactly a creamy bokeh; there's some actual detail there. The details in the far distance aren't razor-sharp. Problem? Not unless this was taken on a clear day in the desert. (Pictures taken in the desert tend to look a little bit fake to people who've never been there because they are overly sharp and saturated in the distance compared to pictures taken anywhere else.)

You are not the victim of poor optics, nor is there a particular problem with your technique. You are dealing with humidity and atmospheric haze in the city. You might be able to cut it somewhat with heroic filtration, but not enough that you'd actually notice a difference when you're not pixel-peeping. Things at that distance just aren't going to be as sharp as things in the foreground. You'll notice this a lot more with sharp geometric shapes, like buildings, and with lights that are going to develop a greater "halo" shining through that much wet and filthy air.

Answer 2

On a second look in the full-size photo, the foreground seem to be pretty sharp and the distant buildings are starting to blur.

At f/5.6 the DOF isn't going to be great, I am guessing you are on an APS-C sensor but you should still try to maximize DOF.

I would recommend keeping it at f/5.6 but try focusing on a distant object and see if the foreground remains sharp. Focusing on distant object for landscape shot like this ensure that distant objects are in focus and increases the DOF at the same time.

If the foreground is out of focus, try moving the focus closer.

I don't know what lens are you using but take a kit lens for example typically it is most sharp at around f/8.0 however that does mean you need to further bump up the ISO.

Maximizing the DOF should give you a sharp photo when everything is in focus.

Answer 3

F/5.6 will be the sharpest aperture to work with ( your gear diffraction limit), but that image looks like as sharp as it is going to get with a cheap lens. If it is windy the building itself can actually move, but I don't see any signs that it have when you took that picture. It also looks to me like the DOF/infinity is set up right. The "glow" looks like digital sharpening.

I don't know if your remote is wireless, but if not then you can set up your camera to timed delay.

If you do F/8 it wont be darker if you go for double exposure time. If it cannot, go for ISO 200. I read in reviews of your camera that IQ is identical on 100 and 200.