f16 or greater

Aussieroo

I am slowly coming to grips with the Fstops on my 30D and selected lenses. I was wondering though where and when others would use greater than f16 to good effect? How much improivement is there in f32 for example in DOF compared to f16. Distant landscapes seem to benifit from f16 but further than that there appear to be little visible difference to me. The one area I wondered is if one was to use a wide lens to say, shoot a running river rapids or water fall trying to keep DOF from close forground to distant background. Would a greater than f16 benifit this type of shot?

jfriend

Aussieroo wrote:

I am slowly coming to grips with the Fstops on my 30D and selected lenses. I was wondering though where and when others would use greater than f16 to good effect? How much improivement is there in f32 for example in DOF compared to f16. Distant landscapes seem to benifit from f16 but further than that there appear to be little visible difference to me. The one area I wondered is if one was to use a wide lens to say, shoot a running river rapids or water fall trying to keep DOF from close forground to distant background. Would a greater than f16 benifit this type of shot?

Macro photography is the only place I ever use an aperture smaller than f/16. Even at f/16, the higher resolution cameras (with APS-C sized sensors) are starting to lose sharpness from diffraction so I usually don't shoot over f/11.

In macro photography where depth of field is incredibly shallow, it is sometimes worth it to sacrifice a little sharpness in order to expand the depth of field.

Aussieroo

Thanks John,

this is the conclusion I was coming to but want to hear it from others. I wonder then why most lenses offer us those options. I guess it is easier and cheaper to make f32 or greater than f2.8 or less to f1.2

I have for the last 7 months been concentrating on macro work and learning the craft and have come to the same conclusion as you through trial and error. I try not to go past f11 and I find that setting to be the "sweet spot" on the Canon 100mm macro.

I have in the past been tempted to go smaller than f16 for one reason or another and generally been disapointed with the results.

jfriend

Aussieroo wrote:

Thanks John,

this is the conclusion I was coming to but want to hear it from others. I wonder then why most lenses offer us those options. I guess it is easier and cheaper to make f32 or greater than f2.8 or less to f1.2

I have for the last 7 months been concentrating on macro work and learning the craft and have come to the same conclusion as you through trial and error. I try not to go past f11 and I find that setting to be the "sweet spot" on the Canon 100mm macro.

I have in the past been tempted to go smaller than f16 for one reason or another and generally been disapointed with the results.

With 12 megapixel 35mm cameras (whether film or full frame digital sensors), the effects of diffraction are much less and you can stop down more than with APS-C sensor sized cameras so the smaller apertures may be more useful on those cameras and many dSLR lenses are designed for use with full frame sensors. Plus, it costs almost nothing to offer a smaller aperture so why not. A larger aperture needs bigger and more challenging optics. But a smaller aperture just needs an aperture diaphragm capable of making a smaller opening while still retaining it's mostly round shape.

Here's an interesting article on the effects of diffraction at different apertures.

Glenn NK

I've found that finding the sweet spot for any particular lens isn't all that difficult - without even taking one shot.

Go to: http://www.photozone.de/Reviews/overview

And select the lens you're interested in, for example the 100 f/2.8 macro:

http://www.photozone.de/Reviews/Canon%20EOS%20Lens%20Tests/45-canon-eos-aps-c/167-canon-ef-100mm-f28-usm-macro-test-report--review

Page down to the MTF charts. This lens is good at f/2.8, gets better at f/4 and f/5.6, then drops a bit at f/8, then drops quite a bit at f/11, and by f/32 has really gone to pot.

Wide open, the entire area of the glass is being used, so at the edges, the resolution isn't at its best because the lens can't "pull" all the different wave lengths into sharp focus at one point (different wave lengths are bent by different amounts by glass).

As the lens is stopped down, less of the lens edges is being used, and there are noticeable gains in the central area where the lens is able to focus the various wave lengths closer to a point (light rays are bent as much).

However with even smaller apertures, the diffraction (dispersion of light rays at the edge of an opening) caused by the edges of the aperture blades starts to take over, and this reduces the sharpness of focus.

Typically by f/16, there will be some diffraction losses; it does vary from lens to lens - and with focal length.

SloYerRoll

Glenn NK wrote:

Go to: http://www.photozone.de/Reviews/overview

Thank you VERY MUCH for that link

gus

G'day 'roo

I will use what ever aperture will give me a 25 second (or there abouts) ISO 100 shutter speed for lightning. Against city lights that can easily be smaller than f16. Thus i use it for effect rather than precision.