Which apeture to choose and where to focus?

[sunny_sony]

Hi Friends,

I am learning photography with my DSLR camera Sony Alpha 390. I am interested about landscape photography specially. I am facing the below 2 problems. Would really appreciate if someone can help me out please.

1. When taking landscape photo I am always going for F22 as I know this will give me the most DOF. I am really not sure which occasion I can use F16 and F18 and still get maximum DOF. I am blindly going for F22 every time.

2. When I choose to shoot landscape photo with F22 I don't know where to focus. Should I focus in the infinity or in the middle somewhere?

 

[Big Mike]

Welcome to the forum.

Yes, F22 does give you the widest DOF (unless you could stop down even more), but you should also know that you loose image quality as you stop down that much. Around F8 is usually the sweet spot for most lenses, so if you could shoot at F8, F11 or F16, you will likely get better quality than shooting at F22.

This is the perfect example of when it would be handy to know the hyper-focal distance.

The hyperfocal distance, is the closest point that you can focus on, and still get infinity focus. In other words, everything past your hyperfocal distance will be in focus, and half way back to the camera will be in focus as well.
Things that affect the HFD, are the focal length and the aperture. So you can use a chart or DOF calculator to find out your HFD for your situation and then determine if that will put your whole scene into focus or not.

So for example, lets say that you are composing a landscape and the closest object in the photo is 2 meters away. You are using a 24mm lens. So looking on a chart (for DSLR), it shows me that with a 24mm lens and an aperture of F11, my hyperfocal distance is about 2.8m. So with those settings, and focusing to a point that is 2.8m away, anything beyond 2.8m will be in focus, and anything that is 1.4m closer will also be in focus (half way back). So yes, that would include our whole scene...so F11 would work for this scenario. To take that a step further, checking the chart for F8, the HFD is about 3.8m...so everything from 1.9m to infinity would be in focus, which also works. So the best aperture to use would be F8...it gives us the best image quality and just enough DOF for our scene.

If you do the calculation and it doesn't give you the DOF that you want, then you can either use a smaller aperture or a shorter focal length.

Some lenses also have a DOF scale right on them, which you can use....and you can also get a DOF calculator app for your smart photo/iPod etc.

For more info, check out this site.
Hyperfocal Distance

 

[flyin-lowe]

You beat me to it Mike, that is exactly what I was going to say............. :lmao:

 

[sunny_sony]

Thank you Mike. One of the best explanations I have got and I am very fortunate to have joined this forum. Thanks a ton again..Sunny..

 

[Derrel]

One of the best solutions I have found is to bracket focus. Many lenses have some focus shift when stopped down to taking aperture. Sometimes there's enough depth of field that shifting the focus point a bit closer, or farther, turns out producing a better image. With the camera on a tripod, I think doing some focus bracketing makes a lot of sense. It's not always 100 percent clear-cut as to where the exact "best" focus point is when everything is said and done, especially if the lens suffers from focus shift, as so,so many lenses do!