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Back to Basics Photography: How F-Stop Impacts Exposure


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lesson-5-600x236 Back to Basics Photography: How F-Stop Impacts Exposure Guest Bloggers Photography Tips

Back to Basics Photography: How F-Stop Impacts Exposure  

In the upcoming months John J. Pacetti, CPP, AFP, will be writing a series of basic photography lessons.  To find them all just search “Back to Basics” on our blog. This is the fifth article in this series. John is a frequent visitor to the MCP Facebook Community Group. Make sure to join – it’s free and has so much great information.


In our last article we look at how F-Stop affects DOF.  This time we’ll look at how F-Stop affects exposure.


Aperture is the opening that light passes through on its way to the sensor.  F-Stop effects the amount of light entering the camera and your depth of field.


The choice of F-Stop can change the look of an image by controlling how much of the image is in focus. The F-Stop also controls the amount of light the reaches the sensor.  This is due to using a wide or narrow the aperture.

  • More light is able to enter the camera if the aperture is very wide (1.4 or 2.8).
  • If the aperture in narrow (11 or 16), less light is able to get through the smaller opening.

So… F-Stop has two rolls when creating your images.  That’s the confusing part for most people.  I’m going to try and clear this up.


Which to use f-stop for:exposure or depth of field:

Typically, I choose an aperture based on the depth of field rather than needed amount of light. I do this for two reasons.

  1. I can adjust the exposure and amount of light with ISO and/or shutter speed.
  2. The depth of field you choose lets you change the look, feel and mood of an image.

I usually set my F-Stop for the DOF I want.  If I’m doing portrait work in a park, I may want the background blurred. In that case I choose a wider aperture or low F-Stop number, F4 or 2.8 possibly, giving me a shallow DOF, where the background will be out of focus.  If I’m photographing a scenic, I’ll go with a smaller aperture or high F-Stop, giving me a greater DOF where more of the image would be in focus.


So which is better: shallow DOF or a greater DOF?

DOF can be more of a preference.   The DOF in your images would depend on how you like to present your images.  You may like your background to be soft or slightly out of focus or you may like your background to be sharp, completely in focus.  This is where you need to make adjustment in you exposure to achieve the DOF you want.


I hope as we’re working through these articles, you’re getting a better handle on exposure control.  Next we’ll look at Shutter Speed and its effects on exposure control.  It’s just one more piece to the puzzle that we’re completing together.


John J. Pacetti, CPP, AFP   –   South Street Studios

2013 Instructor at MARS School- Photography 101, The Basics of Photography

If you have question, feel free to contact me at  This email goes to my phone so am able to answer quickly.  I’ll be glad to help in any way I can.



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  1. Karen on January 22, 2013 at 10:22 am

    Thanks for the post… it has me thinking about my shutter speed for indoor sporting events (I’ve attended a couple this past weekend). I usually take outdoor soccer photos with the shutter speed very high, which has been no problem with sunshiny afternoons. My Canon T2i doesn’t do high ISO very well; and the low-light indoor soccer and basketball shots are extremely noisy. I was surprised reading here that 1/125+ can freeze action… I will try lowering the SS (I had it down to 400 for indoor, not wanting blurry action – but still too dark/noisy). I’ll try experimenting again this weekend with an even lower SS… thanks for the hope of a better shot!

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