Depth of field or the risk of diffraction blur

Doing landscape or especially close up photography you trend to use a small aparture to increase depth of field. But that is noth the right way everytime.

Introduction

Closing the aparture on a lens will increase the depth of field, logical the more you close the greater depth of field will be. But especially beginners are badly surprised closing the aparture to maximum or nearby resulting in images that are not crisp and sharp at all.

This penomena is called diffraction blur and occurs, when the light waves hitting the aparture are fractioned and don’t hit the sensor just straight.

The challenge is to find an aparture setting, which gives you the most depth of field on the one hand side, but avoid the negative effect of diffraction blur

Exercise

I took a couple of comparism pictures with the 5D and the 7D.

Despite the fact that this two images didn’t need to close the aparture that much for means of depth of field, they show very clearly that you should avoid very small apartures.

Comparing the images we can state that the maximum aparture on a crop sensor camera like the 7D should be f 11 whereas a full frame camera like the 5D will take f 16.

Taking this into consideration i choose a maximum aparture f 8.0 on the crop camera and f 11 on the full frame to get crisp images. But good to know that f 16 is still usable if depth of filed requires such a small aparture.

Taking a close up with the rela good 100mm/2.8 L Macro lens, the comparism and the lost of sharpness is quite different.

The text areas shows the increasing depth of field, but closing down to f 22 the overall sharpness of the image is decreasing. Needing quite a lot of depth of field on close ups, you should do a stack.

Conclusion

According to the comparism we can state, closing aparture gives you more depth of field, but crisp images are only reached, if you close the aparture not to much. Doing close-ups you can reach the required depth of field by stacking images.

Landscape or close-up photography are not advised to close the aparture more than f 11, especially on crop cameras. This advice is depending on the output size, but i you’re hooked on crisp images, follow the advice 😉

Whta are your experiences with extremly closed aparture, is it working for you or do you have a maximum aparture depending on your equipment. I’ll be happy to welcome your comments/suggestions and of course questions.

ciao tuxoche