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Tuesday, July 17, 2012

Photography 101 {F-stops-What are all those numbers and why you should care}

Sorry for the hiatus.  Life got in the way.

So f-stops it is.
Can I tell you I was kinda hoping y'all wouldn't pick f-stop.  You see it can be kinda confusing with lots of necessary vocabulary, and I promised you that I was going to keep this simple.
But I will say, if you can wrap your head around f-stops, it will come full circle and likely change how you take photos, and affects how happy you are with the images you take.
It was for me.

So sit down, hang on, and bare with me on the vocabulary lessons.

In a nutshell, because I promised you that the Photography 101 posts would be all about keeping it simple and that I would not get into long lessons in physics...
F-stops are a measurement of the size of the aperture.

What is aperture you ask?
Aperture: the hole (or opening) the light travels through in the lens of your camera
F-stop: a measurement of how big (or little) that hole is
Can you see the aperture in this lens?  It's the pentagon-hole thingy in the middle.
Think of it like this-
Pounds are a measurement of weight.
Meters are a measurement of length.
Hours are a measurement of time.
F-stops are a measurement of aperture. 

Aperture and f-stop are terms that are often used interchangeably.  For example-Phyllis the photographer might refer to her f-stop being set at 2.8.  Or she might also say her aperture is 2.8.  Technically, it's her f-stop set at 2.8, but you may still hear these two words used for the same objective.   But you should know that f-stop and aperture are different things.

So here's a typical 50mm lens.  Notice all those numbers on the bottom ranging from 16, (the one in orange) 11, 8, 5.6, 4, 2.8, 2, through 1.4?  Those are the possible f-stops that this lens has.  With this particular lens, the photographer can then choose which f-stop she wants from these possibilities.
You might also hear folks refer to this lens as a 50mm 1.4.  The 1.4 being the smallest possible f-stop for this lens.

Here's the part that trips folks up.  You may want to sit down for this one.  The smaller the f-stop the larger the opening.   And conversely, the larger the f-stop the smaller the opening.  So on this lens the 1.4 is the largest aperture and 16 is the smallest.  
See how the littler numbers have the larger openings? And the higher the f-stop, the smaller the  size of the hole?
You still with me?

Which naturally leads to the question... So which f-stop should I choose and why do I even care?

Long story short and physics lesson aside, f-stop is one of the things that control depth of field.  

What's depth of field you ask?
Depth of field is the distance of stuff that's in focus in you photo, and depth of field is one of the first things the beginning photographers want to know how to control, even though they may not even know it.  One of the first questions I get from new photographers is "how do i get that blurry background?"  The answer is to manipulate your depth of field, and one easy way to do this is by having a large aperture (that would be the small numbers) when taking a photograph.  Go back here to this Photography 101 post to learn more specifically how to do that blurry background.

So let's talk depth of field for just a bit---
Depth of field can be deep, short, or somewhere in between.  
In a photo that has a deep depth of field, there will be a large distance of subject matter (from front to back) that will be in focus, from the foreground to the background.
In a photo that has a short depth of field, there will be a small distance of subject matter that will be in focus.

This photo has a short depth of field.  Very little distance, from front to back, is in focus.  Notice that the foreground table cloth is quite blurry.  As is the background of sliced radishes and even the colander.  The distance of stuff that is in focus is only a inch at most.  This photo was taken with an f-stop of 1.8... which can also be written as f/1.8.  
This photo has a long depth of field.  Everything is in focus, from the ground in the front, to the kiddos, all the way to the back ground.  This photo was taken with a f-stop of 8.0... which can also be written as f/8.
Again, short depth of field, where foreground and background are out of focus.  But Both Tess and Jude's  faces and his hands are in focus.  f/3.2
Long depth of field as almost everything in this image is in focus.  f/8.0
Keeping it simple
Lower f-stops give smaller depth of field.
Higher f-stops give deeper depth of field.

So one of the big reasons you might care about all those f-stop numbers is because they are a way to manipulate your depth of field, allowing you to capture the image you envision.


  1. THIS is very helpful. Thanks for keeping it simple. Me likey.

  2. My internet takes the cake (and the comments).

    Basically I have a Nikon D40 and one lens (I have 2 and they range from 18-200) none of them have the 5.6 or "." anything. So am I trying to understand a camera that doesn't show me those markings, or is my camera too old or something? I did buy it when we lived in Germany about 5 years ago, so maybe it's just cause it's German.

    The only time I've really taken it off the auto setting, I got a completely white picture that I could never get into focus. I think I need photography 90 before I could even tackle photography 101.

  3. "I get it!" said she, jumping up and down. That manual has been sitting in my camera case for months now. Thank you! Someday I will brave manual and instead of getting lucky, I will actually take a good picture.

  4. Thank you, Nancy! I think I understand. Now to try it out.

  5. Oh my goodness! I completely understood every word of that post...thanks for the simplicity!

    I've never posted before but I've followed you for quite a while. This morning I just had to comment because I have taken photography classes, became frustrated with my manual, and been stuck on automatic for the longest....this one post and I got it, LOL.
    Thank you, thank you!

  6. You are a teacher at heart! Great post!

  7. Thanks again, Nancy. I look forward to every post. Question...but: how does lighting affect aperture and aperture affect lighting?? Can you pretty please expound upon that a bit.

    Also, here's a far-out and crazy idea...did you ever think of giving a critique on a photo here and there. I know that I need to train my eye to see what's wrong with a photo also..but I'm just not sure how to do that. I don't know, when looking at a photo (for example) "well, this is overexposed, the shutter speed should have been quicker" or something like that. Does that make any sense at all!! Ughh..sorry for the lengthy comment. I get excited by these posts and the fact that I am actually beginning to learn something haha.

  8. Cherie,
    This post had so much in it, I just didn't want to get to complicated. But since you asked...
    ---A larger aperture/smaller f-stop (for example if you wanted a short depth of field) means more light will come in your lens because the hole is bigger. And thus lower ISOs and faster shutter speeds are possible. If there's not much light available, you can open up your aperture with smaller f-stops and get more of the available light in through the lens.
    ---A smaller aperture/larger f-stop means less light will be coming in your lens, and a higher ISO and slower shutter speed will be needed. If you selected a smaller aperture/higher f-stop, (for example if you wanted a deep depth of field) you'd need to compensate since there would be less light coming in your lens, by increasing your ISO and/or making a slower shutter speed.
    That's a LOT to absorb.
    Does that make any sense?

  9. It does. I'm trying. And working. It makes sense and I understand it...but each and every time I have to Stop. Think it through. Ponder. That takes time.
    So you are saying I can choose my desired depth of field FIRST and then adjust shutter and ISO accordingly to match it.?
    I am hoping and assuming that the more I do it, the more natural it will become and the more success I will have....holding onto that hope. I never seem to achieve good clarity yet either..but...I am working :) ...and reading!!!

  10. Wow. You are really good at explaining all this. THANK. YOU. I will now go and read all your photography lessons! I found you via Craft Gawker.

  11. I am definitely going to study your photography lessons! Thanks for a wonderful tutorial. Cheers from your newest follower!

  12. OH, so its just like the pupils in our eyes, right (I am soon to be an ophthomalogy resident this summer once I finish up med school)? When theres more light, they get smaller, and when theres less they get bigger. If you are in a really dark room and your eyes have adjusted, and then a light goes on, everything seems so much brighter because so much light is coming through big holes. And if your eyes have adjusted for a bright room and then the lights go off, it seems so much darker than it really is because your pupils are so little.
    The same goes for photography, right? If you were to adjust all your settings for a darker place and then turn on the light, it would be too bright (or the fancy word "overexposed" as I just learned) and so you would have to make the aperure hole smaller to let the right amount of light in.
    Am I getting this right at all or am I completely wrong? I don't even own a DSLR and I have no photography experience.


    1. Yes, Beth, you are totally getting this right! It's very very much like the pupil of the eye! I'd say you're ready for a dslr!


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