DSLR: Force Sharper Images on Night Pictures

Night photo: F8, ISO 100, shutter decided by Sony SLR-A58

If you want a photo that is sharp all over you could select an aperture priority, and just shoot. But then the camera will try to get an image with a fast shutter speed. In order to do so the ISO-number will rise. As a consequence the image quality will suffer.

Here is a simple recipe:

• Set aperture to F8
• Set ISO to around 100 to 400 or so
• Let the camera calculate the shutter speed

As a result of these settings you will get a fine depth of field because the aperture is F8. The camera cannot choose a lousy quality of the image, because the ISO is defined as 100 or a bit more. Since the ISO and aperture are fixed the camera is forced to calculate a longer shutterspeed - and as a consequence your picture will be sharper with more details. 

Lens Sweet Spot

Aaarhus seen from my kitchen window today.

During the hollidays I'd like my DSLR pictures to be sharp from the foreground to infinity. Most lenses has a sweet spot, where pictures are better. When you've found that it's a matter of point and shoot.

Some rules of thumb if you want a sharp picture from foreground to infinity. 

When in doubt, try F8 - else try:

• 24mm ~ >= f11 <= f16.
• 35mm ~ f16 (street photo, 2m -> infinity sharp).
• 50mm ~ >= f22 (2m -> infinity sharp).
• > 80mm (no sharp foreground) f5.6 (from 100 m. -> infinity).

For most lenses the general rule is low f-stop + 2. 

• e.g. 1.8/50 ~ f4.

If you want to find the real sweet spot for a lens, try settings as above. Shoot several pictures, and compare the sharpness on the PC. For every new picture add an f-stop. 

Source, see this article.

A nice calculator is found here. Here is the result of the hyperfocal calculator:

From: http://www.cambridgeincolour.com/tutorials/hyperfocal-distance.htm 

Hyperfocal Distance

On Wikipedia you can see the formula for hyperfocal distance:

"In optics and photography, hyperfocal distance is a distance beyond which all objects can be brought into an "acceptable" focus." (from: Wikipedia)

In theory we could create an app for the calculations, but ... in the field you just need something that works. I guess the rules of thumb will do the trick.

Sony a58
Change the autofocus area to 1/3 (probably it's in the center). Then you  should have the correct focus, provided that the f-stop is on the sweet spot. Set aperture between >= 8 and <= 11, and set ISO to auto. Then it's a matter of "point-and-shoot". That would be a good street or landscape setting.


Tamron B018S
Look at this site for specifications.

There's a video with a german photographer using apertures ranging from 5 - 11, but more than often 5 or 8. 

Tip: 

• Try manual focus.
• Use A on your camera's settings ring.