which f numbers for what?

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Seijik

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hi guys and gals, im just after a little advise on what f numbers i should be using?

i understand what they are, just not which one's will give me the best shot and what impact different f numbers have on a shot?

any advice would be great!
 
larger F numbers (smaller aperture size) will give you larger depth of field ... so if you take a photo of a flower which is close to you... you will still see the rest of the garden behind for instance. F22 maybe.

If you use a smaller number (F2.8) (wider aperture size) you will blur the background behind the flower.
 
yea i understand the depth of field, which aperture's give you the best sharpness and colour, do different apertures give a different look to the shot, like darkened edges etc?

i took some pics of a sunset, and the sharpest picture i got was from 3.5, whereas i thought that a higher f number would have given me a wider range of sharpness through out the picture?
 
Have a look at this site, it is interactive and allows you to see what effect adjusting the different settings on the camera have on an image...
 
Flash In The Pan said:
Have a look at this site, it is interactive and allows you to see what effect adjusting the different settings on the camera have on an image...
Click to expand...

That is great I have been trying to explain the interaction between all these variables to my wife and daughter!
 
Seijik said:
i took some pics of a sunset, and the sharpest picture i got was from 3.5, whereas i thought that a higher f number would have given me a wider range of sharpness through out the picture?
Click to expand...

You are right in the fact that the optimal range for a lens is higher, around f8-f11. Where you say that you were only sharp at f3.5, will have other factors mixed in, I imagine that if you were only sharp at this aperture then your shutter speed will have been incorrect (to slow) thus anything over f3.5 will have been blured due to not enough light in the scene.

Also your ISO settings have an impact too @100 you'll need good light with a large F number, the higher the ISO number the less light you need, again they are all linked and can all effect your results. Try setting your camera @ ISO 100 then put in into AV (aperture priority) mode and then have a play dial in say F2 see what you get on your shutter speed, anything below 1/30th you will be VERY lucky not to blur being handheld. Then move up to F8 and try again. Its all about experimenting, trial and error, trust me, its mostly error as we've ALL done it. :D
 
thanks for your replys, i think i just need to experiment lots and try and find a book!

the problem i had was that it was a really nice shot and i didnt have my tripod :'(

i didnt want the iso too high as i wanted a crisp shot, but then i knew i would struggle with the light, i took shots ranging for f3.5-f14 i cant remember the shutter speeds but ill have a look.

if the opimal f number is about 8-11 should you try and shoot at this f number all the time? if so, how come the mega expensive lens's are f1.4?
 
Because their optimum range will start at around f4 or 5.6 rather than f8 a lot of the time.

They will also be sharper at the widest apertures due to better engineering etc. than a consumer grade lens.
 
i see! i'd better start saving then! lol whats the reason for them being sharper at a higher f number?
 
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