Teach me about f-stop

[hmiles619]

I think I've grasped everything except f-stop. I mean I know what the definition of f-stop is. I just don't know how to apply it. Anyone have a good resource? Example? to help me grasp this concept.

[bburton]

http://www.pbase.com/wlhuber/the_basics

[Allen]

Originally Posted by bburton

http://www.pbase.com/wlhuber/the_basics

Great link...thanks.

[RandySmith]

Hollis -

This might be a silly experiment ... but maybe it'll help you grasp the concept ...

Take a piece of cardboard and make a really small hole in it.

Hold an object out in front of you and focus your eyes on the object and then the background. It should be difficult to see them both "in-focus". ... Now, look through the little hole in the cardboard at the same object. Both the object and background should be in focus.

This represents in a simple way, a large aperture (shallow focus) f1.0, f2.0, etc.

The small hole represents a small aperture (large DOF) f22, f32, f64 ... etc.

My two cents.

Hope this helps.
Randy

[venchka]

You could do that, or shine a light in someone's eyes and watch their iris (same thing in a camera lens) open and close.

Small number=big opening=lots of light=shallow depth of field=faster shutter speed.

Big number=small opening=very little light=more depth of field=slower shutter speed.

Piece of cake!

[brad]

On your table at home, set up three objects (big enough to focus on)... Set one on the close edge of the table, one in the middle, and one on the far edge... stand as close to the closest object as you can and still focus on it with your lens.

(You will want a tripod for the next part.)

Focus on the farthest object and set your f-stop as low as it will go on Av (Aperture priority mode).. take the pic. Move the f-stop up one notch and take another pic... do this until you run through all the f-stops.

Do the same thing twice more.. the second set focusing on the middle object and the last set focusing on the closest one.

Compare the pictures.. see how the objects other than the one you are focusing on are sharper at higher f-stops? That will show you how the DOF is changed by the f-stop.

Now compare the same f-stop setting (around 8.0) across all three focus points (when you were focusing on the farthest, middle, and closest objects) .. same f-stop, but three different DOFs... this demonstrates how your distance from the object you are focusing on impacts the DOF.

(We do this exercise in my basic camera class.)

[lhdvies]

Excellent resources on this thread-thks-another link to tie the f stop into focal planes, depth of field amd shutter speeds is www.dofmaster.com/dofjs.html - also the book "understanding Exposure" by Bryan Peterson explains the f stops usage about as simply and as thorough as anything I have seen on the subject.

[chloew]

Here's another related lesson...

http://www.morguefile.com/archive/cl...m.php?lesson=2

[NikonShooter]

Great Link...thanks for posting.

[venchka]

I didn't wade through the links. If this was covered, sorry.

Depth of field extends approximately 1/3 in front and 2/3 behind the plane of focus. Keep this in mind when selecting your focus point. It's too bad modern zooms don't have decent DOF scales. They really are handy and quick.

[PhotoByLeal]

Originally Posted by hmiles619

I think I've grasped everything except f-stop. I mean I know what the definition of f-stop is. I just don't know how to apply it. Anyone have a good resource? Example? to help me grasp this concept.

Hollis,

I found this chart that might help you and others out!

http://kaptures.net/sunny16_cheat.xls

There is also a infrared chart!

Here you go Ming!
http://kaptures.net/sunny16_IRcheat.xls

It is pretty cool to have handy!

Later,
TxmexNitro - Angel

[Torrey]

So, from the tutorial that bburton posted, given the image at the url below:

http://k41.pbase.com/u11/wlhuber/upl...56.basic08.jpg

...if you + the EV, will this actually keep focus on the main subject while blurring the background, since you're effectively decreasing the f-stop?

[PhotoByLeal]

Originally Posted by Torrey

So, from the tutorial that bburton posted, given the image at the url below:

http://k41.pbase.com/u11/wlhuber/upl...56.basic08.jpg

...if you + the EV, will this actually keep focus on the main subject while blurring the background, since you're effectively decreasing the f-stop?

Sorry this is all I get!

Forbidden

You don't have permission to access /u11/wlhuber/upload/41450056.basic08.jpg on this server.

[Torrey]

try it one more time...i was having some trouble getting the link to work as I edited

[PhotoByLeal]

Originally Posted by Torrey

try it one more time...i was having some trouble getting the link to work as I edited

still !