Appropriate aperture to use

[D-Wade]

Hello, i've been reading a lot of stuff here and there, but still some are unclear to me.
It is about appropriate use of aperture.
I currently have a 17-50mm f2.8 lens and a 50mm f1.8
does that mean I have to shoot at 2.8 and 1.8 respectively?
I know aperture controls the DOF, but let's say on a sunny day and I'd be taking a group picture, it means for everyone to be sharp i have lower down my Aperture, but to what extent?
Is there any such guideline?
i.e. Sunny day
portrait 2.8 for bokeh also
landscape 9~11
group picture 4~5
when to use lets say 22 or 16 or 32, i have taken shots at 32 with waterfalls, it looksreally nice, but I dont really have a grasp of any guideline or expected result for a given aperture.

i know for low light condition I dont have choice but to increase the aperture, my query is typically on a sunny day.

Is my query valid?
Still a noob here and learning

 

[driveanegg]

Hello
There is no hard and fast guideline.
You dont HAVE TO shoot at 2.8 or 1.8, its just the max that it will open up to ....

You may want to consult the DOF calculator
Google : - Depth of Field Calculator

Keep shooting

 

[ahbian]

You just need to shoot more to know what to expect with different apertures.

If there is a luxury of a reshoot, take the shot and view in your computer.

If you need it on the spot, see if the DOF button on your camera helps you.

 

[sinned79]

if u want blurred background - shoot from f1.8-2.8
if u want overall clear photo - shoot from f5.6 and above (adjust to your needs)

 

[sampan]

A few examples when smaller aperture would be used
1. when we want star-brust from sun or lamp
2. panning in a bright sunny day
3. night shot for light trail from moving vehicles
4. silky effect for flowing water
(there would be more, but these are what came to mind immediately)

In situations 2,3,4 described above, the small aperature is used becuase we need longer exposure.

 

[chalib]

Have you read this

http://www.clubsnap.com/forums/showthread.php?t=309544

 

[Octarine]

I know aperture controls the DOF, but let's say on a sunny day and I'd be taking a group picture, it means for everyone to be sharp i have lower down my Aperture, but to what extent? Is there any such guideline?

More to read here: Understanding Depth of Field

 

[Rashkae]

Experience helps more than a search for a magic formula.

 

[clioboy]

set to Auto ;p

 

[D-Wade]

I have a full understanding about the DOF for a certain Aperture, i think to answer my question would be the DOF calculator, many thanks masters =)