Depth of field plays such a large role in the overall look and feel of a photo that I encourage all of my workshop students to quit using program mode and take control of their aperture and depth of field. Letting the camera make this choice seems crazy to me, yet I still see people doing it all of the time. In my latest video post, I explain how and when to use a shallow depth of field vs. a large depth of field, and I talk about using the hyperfocal distance for maximizing your depth of field.
Nice overview of DoF topics. Except that it seems your presentation implies a full frame 24x36mm sensor? While the format limits your time in such nuances, it might help for you to point out that there are variations in performance with sensor size. I’m guilty of not thoroughly researching, but as a ‘cropped’ DX sensor user, I’ve generally garnered that much beyond f/8 or so this format is prone to diffraction. Could you perhaps point us to what you consider is a good resource for digging into these details?
Hi JDB – thanks for pointing this out. Yes, I was primarily speaking about full frame sensors in regards to depth of field. The techniques for calculating hyperfocal distance on cropped sensors is the same – you just need to use a different chart, and any on-line or mobile phone depth of field calculator will do this for you.
As for the issue of diffraction, it is true that for each sensor/lens combination there is a point where stopping the lens down further will result in more depth of field, but an image that is less sharp overall. I don’t think you can make a generalization that F8 is the aperture that this occurs for all cropped sensors. I think it depends both on the quality of the sensor and the lens you are using. I’ve found that with my Canon F2.8 L lenses, that F22 results in an image that is too soft for my liking, so most of the time I will only stop down as far as F16. My guess is that those same lenses on a cropped sensor would perform similarly since the sensor is capturing a smaller and higher quality circle of light from that lens.
However, with smaller maximum aperture lenses, diffraction might become a problem at bigger F-stops like F16 or F11, but I think you’d really need to perform your own tests with each of your lenses on your camera to determine what you’re comfortable with. It really does come down to personal preference, as well as the final use of your image – are you making 8 x 10 prints or 30 x 40?
For example, another OP blogger, Ian Plant, prefers the extra depth of field for some images despite the loss of sharpness caused by diffraction – he wrote about this last summer: http://www.outdoorphotographer.com/blog/ian-plant/2011/07/lens-diffraction.html
Sorry I can’t give you an exact answer on this – I think there are too many variables to consider.
Cheers!
-Jerry