Photography tips – f-stops

This tip is for those of you that have a DSLR/SLR and can control your f-stops.  An f-stop is defined as:

The literal interpretation of the f/N notation for f-number N is as an arithmetic expression for the effective aperture diameter (input pupil diameter), the focal length divided by the f-number: D = f / NSource: Wikipedia

Get that?  Yeah, me neither.  Basically, it is how wide-open you have set your lens aperture.  The more wide open you set your camera lens, the more depth of field that will be created.  Tracey at Picture This had a good discussion on this subject a little while ago.  Be sure to read the comments, too.

In this installment, I was just going to give you a few basics of where you want your aperture set for specific conditions.

wide open = small number

closed up = larger number

Wide open a.k.a. around f2.0.  When you are shooting wide open, you will have a narrow focus area and great depth of field.  Lots of lovely blur in that background.  When the lens is wide open it lets in a lot of light, which is also fabulous for shooting indoors in the winter time.  Usually in order to get this low, you need a prime lens or a high-end (expensive) zoom lens.  You can usually get a 50mm 1.8 prime lens for around $120.  It is well worth it.

Having the lens wide open is tricky.  You really need to make sure your subject is parallel to your lens or very close to it.  Your camera is focusing on a specific spot that you have chosen, and that focus area is very narrow, inches really.  If your subject is at an angle and you focus on the eye closest to you, then the eye furthest from you may be out of focus as it is beyond those scant inches of focus area.

Also, make certain that you are focusing on the eyes or the bridge of their nose.  Anything else and it will look like an out of focus shot.

Example:  This was shot in our garage where you want that blurred background.  Notice that he is parallel to the camera, so his eyes are on the same focal plane.  The eyes are nice and sharp and you can see how once you move past the eyes the blur starts right away.  That shows how shallow the focal area is when you are wide open.  f2.5, 50mm, SS 640


Want some bokeh – Bokeh? What is bokeh?  That would be the blur behind the subject.  Now you can still have blur without your lens being wide open.  If you are a bit of a bokeh connoissieur, then you know that the higher-end lenses give a better bokeh that say, my lenses.  I, however, don’t care at this point.

Some good parameters would be around f4-f5 for 1-2 people.  Most kit lenses are capable of opening to f3.5-f5 depending on the focal length of the zoom lens.

Example: This was shot in the sandbox under the canopy.  I was fairly close to her, too.  Notice that her whole head is in focus and the background is blurred.  F4.5, 50mm, SS 1/400.


Family shots – It is very difficult to shoot more than 2 people with an f-stop of f3.5 or under.  Unless they are on the same plane, you are probably going to get some out of focus people.  If you don’t like them, I guess that is fine, but I think for most family pictures we are actually trying to include everyone.  Start at an aperture of at least f5 if they are all in a line.  If you have a little staggering, choose an aperture of at least f8.  If you are shooting several rows of people, then you need to bump that number up quite a bit.  Here is a great link for determining how much area will be in focus depending on your lens, your aperture setting, and how far away you are from the subjects:

Depth of Field Calculator

Go look at this link as it is great at helping you determine how many feet/inches you have to work with in the focus area.  The family shot that was posted here was at F8, and my mom was around 10-12 feet away.  The further you are away from your subject, the wider your focus area becomes.

Who cares? – This is the term that Brian Peterson gives to aperture values where you don’t need depth of field.  Click on that link and buy that book, since it is the bible for determining aperture values.  I’m serious…do it now.  Done?  Okay, he suggests a sweet spot f-stop of between f9 and f11 for shooting pictures of these types.  This would be where you are taking nature pictures or where you want the environment in focus as well as the subject.

Example: This was a shoot I did for a friend for her engagement pictures.  It was in a beautiful park in the winter.  I wanted everything in focus here.  F10, 50mm, SS 1/2000, bright sunshine.

Who cares what f-stop

Well, I hope this was helpful and informative.  Definitely check out the links, as they will help aid you in figuring out this complicated measure.

8 Replies to “Photography tips – f-stops”

  1. Ahhh…the mystery of the f-stop. I must get a new lense for Christmas. Mine is just not doing it for me. Thanks. This was a great tutorial.

  2. Boy I have a lot to learn. And a new camera to buy. Start saving my pennies… I NEED a “real” camera!!!! (and maybe some private photography lessons!)

  3. Very informative, thank you! I have this nice new camera and not a clue how to use it. Blog posts like yours have helped me to understand it a tad… now if only I could retain all of this information to use when I’m smack dab in the middle of a park with clouds overhead and everything is coming out blurry. HA!

  4. I got a lovely 50 mm f1.8 lens for my birthday and it has made a world of difference in my photography! I highly recommend an investment like that, especially for indoor pictures. Thanks for your explanation – it’s very easy to follow.

  5. Thanks for getting this info down to chewable understanding. Your pictures are beautiful!

    mama to 6
    one homemade and 5 adopted

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