Friday, August 21, 2009

Friday's Photo Tip - Controlling the Aperture

Friday's Photo Tip - Controlling the Aperture

a violet with a shallow depth of field

Last week's post discussed the job of the aperture and how it controls the amount of light entering the camera.

And I ended the post mentioning that I would help explain why a photographer would want to control the size of the aperture when the camera has a mode for doing this automatically.

Most cameras, both the point and shoot, and the DSLR's have several modes for capturing images.

The most popular one is the "auto" or the "program" mode as it lets the camera make all the decisions - and it does a great job most of the time.

There are other options to pick from too, and they include shutter priority, aperture priority, and manual.

I use manual off and on, but when I am in a situation when I don't have the time to think and fiddle around, I pick the aperture priority mode. It is my favorite one most of the time.

This mode allows me to set the aperture at what I want, and the camera will choose the correct shutter speed to compensate for the light.

I am a bit of a fanatic when it comes to my depth of field, and this is something that is controlled by the aperture.

The size of the aperture and my focal distance will determine how much of the photo will be in focus.

And the handy little button next to my lens that allows me to view the image by closing down aperture is also another one of my favorites.

I can see exactly what will be in focus and it can be a huge help in determining if it has that nice bokeh background that I like.

Now, how does one use the aperture to control the depth of field?

Once again it has to do with those f-stop numbers and how big the aperture is.

The smaller the number, the more shallow the depth of field will be and less will be in focus.

The higher the number, the wider the depth of field will be, and more will be in focus.

When shooting macro, the depth of field is very limited to begin with, so I try to get a fairly high number to get more of the image in focus.

This is not always easy, because if you remember from last week, the higher the number, the less the light there is coming into the camera.

And that means a slower shutter speed to compensate for this, which in turn usually means I need to use a tripod.

The above image has an f-stop of 5.

By pressing the aperture button beside the lens, I could see that I had the very center of the flower in sharp focus and the petals were acceptable though not as sharp.

And the background - it had that nice bokeh that I was hoping for.

If I had increased the f-stop to a higher number, like 22, then all the flower, and pretty much all the grass and the background would be in fairly good focus.

A lower f-stop, like 2, would have just the very center in focus, and the petals would have no definition and would blur into the background too.

By controlling the aperture opening with the f-stop numbers, the photographer has much more creative control over their photo and how they want it to appear.

Try experimenting with the different f-stops while shooting one subject and notice the difference in each photo.

The good thing about digital cameras - they record all the exif info with each photo. That ends all the writing down we used to have to do when shooting our images so we would know the shutter speed, f-stop, ISO, focal distance, time, date, and so forth.

I hope I have explained this so that is easy enough to understand. If you have any questions, please let me know.

Thanks for stopping by and happy experimenting with your aperture - it's one of the best parts of using a camera!


  1. Yes for me at least you have made this very easy to understand. I have been practicing. I just wish my darn manual was more user friendly. It is very difficult to read. It sends you from one chapter to another just to figure out exactly how to change the settings.

    Thank you Kathy and I hope you have a great weekend!

  2. HI Jackie - glad it helps, and yes, the manuals are never very user friendly.

    Hope you have a great weekend too!

  3. Good article, Kathy. I, too, use aperture priority quite frequently -- mainly so that I can control the depth of field.

  4. Hi Kathy,
    I hope you are enjoying your Sunday afternoon. i was down with a sore throat yesterday and now I am ions behind on everything!!

    It was so kind of you to stop in and you are very welcome!

  5. Thanks for making the DOF a little easier to understand in relation to the F stop, excellent DOF work on your image.

  6. really really really handy friend. will be visiting u in times...

    frndly neibourhood


  7. Kathy another great educating post. Thanks for all the info. You really know your technical stuff, Anna :)


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