It’s first really hot and sunny day this year. Lying on the grass I hear buzzing bees by my ear and a whisper of wind in the trees. Somebody could ask “Why is she so damn lazy?!”. In fact sipping an orange juice with ginger I am reflecting on some theoretical and philosophical issues. I was only 10 years old when my dad gave me my first czmera – an old Smiena. Maybe because of that, now I am fully aware of the fact that the smaller is the aperture, the greater is depth of field.
However, a practice shows that too large diaphragm (small aperture) may cause a loss of quality of the whole photo – the edges of all objects are blurred. I’ve never had the ambition to make ModeBlog a physics tutorial, so mainly I will use the image:
Comparative photos, which were taken with extreme f-stops:
1/250s, ISO 100, f=5,6 (large aperture) – only one diamond is in focus, the rest is blurred. At the same time lines, which point the diamond cut up, are very clear, while gold has the correct colour and sparkle. (Canon 70D+Canon 100 mm f/2.8L EF Macro)
1/6s, ISO 100, f=32 (minimum aperture of my camera) – I’ve achieved seemingly greater depth of field, although nothing on this picture is sharp enough- gold has tarnished and the stone has lost its contrast.
Well, the thing we are struggling with now is called diffraction. This occurs when the light is moving along a straight line and then encounters an obstacle or a slit. (Canon 70D+Canon 100 mm f/2.8L EF Macro)
A diaphragm is the main culprit of this diffraction. Instead of using a maximum aperture for a given device, it is better to find a happy medium. This means setting a small depth of field (set 8 and never change), elongating the distance from the object, using a lens with a smaller focal length (link to the article), or reaching for the more advanced techniques, like focus stacking (read an article) or glass with tilt-schift function (link to the article).
I hope that you have found this article useful. Knowledge of diffraction is effortless to apply (in fact, it won’t be the main issue in most circumstances) but can have terrible consequences for those who are not aware of it.
The other problem with the small aperture is a long exposure time, which increases the image noise. In the extreme cases there is a risk of camera shake.
Written and photographed by:
Dominika Apanasewicz www.studioavior.pl