You're Smarter Than Your Camera - Other Aspects of Aperture and Controlling Depth of Field

February 20, 2015  •  Leave a Comment
You're Smarter Than Your Camera - Other Aspects of Aperture and Controlling Depth of Field
Good morning to you and thanks for reading...my third and final blog on aperture!  Hopefully, by now, you are getting to grips with what changing the aperture can do for you and your photographs and you are starting to feel like you can capture more of the kind of shots you want.  This blog covers a little more about depth of field as well as how to get as much of your subject in focus.  I will also look at how we can use aperture to get those great starburst images.  Finally we will finish with some of the problems when photographing with smaller apertures.
Thanks for reading and enjoy the blog.
Tracey
Ok....if you've had enough of aperture, I don't blame you :-) and I certainly don't want to bore you but there are a few more technical aspects to aperture that may interest you both when photographing and when choosing lenses to use or buy.
Last time we introduced the term 'Depth of Field' and showed that this meant how much of our image was in focus. We pursued taking images with very little in focus....this post is different.  We're going to look at images where we want most of the subject in focus.  Using small apertures will give you extensive depth of field and combined with the right lens, this could stretch from 1 meter to infinity.  This is more like what we need when photographing a landscape or architecture where we want as much of the subject in focus as we can get.  
So...where is the best place to focus when photographing a landscape?  There is a little trick we can use to maximise the depth of field.  Introducing hyperfocal distance - this is roughly defined as the focus point that places the furthest edge of the depth of field at infinity - essentially, it is the closest point to you that you can focus on to still allow the further point in the image to be acceptably in focus.

Ok...and to demonstrate with another one of my sketches....no points for skills her I'm afraid, but hopefully it helps to get the point across :-)
Cutting to the chase....in many examples, if you focus one third of the way into your image, you will be focusing around the hyperfocal distance.  There are of course exceptions to this but I'm not going to bore you with them here - If you are keen to calculate the hyperlocal distance for your lens use the calculator in this article - http://www.cambridgeincolour.com/tutorials/hyperfocal-distance.htm.
Ok - more of the fun stuff!  lets get those starbursts right!  Of course you shouldn't look directly at the sun, but if you have an object between you and the sun that hides most of the light, but allows a little bit to creep around it you can photograph a starburst.  For the image below, I used an aperture of f10 and got a beautiful starburst.
Diffraction
Oooh, remember those nasty physics lessons :-) Here comes a term from one of them that describes a little problem we experience with smaller apertures.  Take a look at these two images below.  They are of the same subject and I have used widely different apertures to take the photograph.   You can notice that the veins on the far right leaf of the first image are not as clear as those on the second image.  
This image was taken with an aperture of f16
This image was taken with an aperture of f4.5
This problem is because of diffraction.  When the aperture is small, the light rays are effectively bent to get through the hole and this has the effect of making the image less sharp.  There isn't anything you can do about this and most lenses have an optimal aperture, beyond which, the sharpness of the image is compromised.  Different lenses have different 'sweet spots' and it suffices to say that you should be cautious of going right up to the smallest aperture to get the greatest depth of field as it will compromise the sharpness of your image....whew!
Focus stacking - If you are a fan of photoshop and editing, you can use a technique called focus stacking to ensure that more of your image is in focus.  Basically you take several images of the same subject with different elements of the image in focus and then you stack them together retaining all of the in-focus elements.  There is a great article on this in cambridge in colour and you can research photoshop techniques to help you. http://www.cambridgeincolour.com/tutorials/focus-stacking.htm
I could carry on, but I'm afraid I would lose you.  But do get in touch if you have any questions or comments, I am always happy to research topics for readers and love a challenge :-).

Lets get onto this weeks project.
Your Challenge -

Continuing with the camera in the aperture priority setting.  Remember this allows you to change the aperture of the camera whilst keeping all of the other settings automated.

Experiment with getting a starburst photograph - trees and buildings make great objects to hide behind.  Start with your aperture around f10 and increase it (making the aperture size smaller).  See how the settings change your starburst image and try to notice if you are experiencing a drop in image quality as you get past f13.

You may also get unwanted lens flare when shooting in bright light - this is where there are additional light patches in your image.  Try using a lens hood or changing your angle if you are having unwanted flare.
Next Time – Racing onto Shutterspeed!  I will post this early March so keep a look out and in the meantime, enjoy your photography :-)
As always, do get in touch if you don’t understand anything or if you would just like to comment.
Thanks again,
Tracey
 
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References
 
www.wikipedia.org
Complete Guide to Digitial Photography by Rick Sammon
www.cambridgeincolour.com
www.imagemaven.com
www.luminous-landscape.com
Copyright © 2015 tracey medcalfe photography, All rights reserved.

 


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