You didn’t say what focal length. Assuming you were using 200mm at 20’, f/11 the depth of field would be 4”. 50mm at 20’, f/11 would be 5’9”
The one app I am using to calculate these numbers doesn’t want to use an aperture smaller than f/11. The other app says 2’11” for 200mm, f/22 at 20’ but I am not sure I quite trust that. Note that 1 - using f/22 you are going to be encountering diffraction softening which would certainly affect the small flowers. 2 - the 50-200 is not known to be super sharp. And most zoom lenses of that variety, even the very best, will be “soft” when used at longer focal lengths like 200mm. 3 - Shooting from 20’ away, with a 200mm lens you need a rock-solid tripod, use mirror-up remote trigger. A reasonably fast shutter speed is also called for. If you are shooting at f/22 then you will either need a lot of light or a high ISO. In short, there could well be other factors which affect your image’s apparent sharpness other than the issue of proper focus and depth of field. BTW, I am not sure why you mention auto-focus and infinity if your question is about depth at 20’. Did you autofocus at something infinitely far away and then recompose, thinking that that would give you enough depth? You would probably get better results if you manually focused about 1/3 into the bed as Jack said. But if you want the flowers in front in particular to be in sharp focus, then manually focus there, then slightly nudge the focus an inch or two deeper into the scene. Two other options would be to focus stack as Mark C is doing or to buy a tilt lens. stan On Apr 11, 2015, at 9:16 AM, Eric Weir <[email protected]> wrote: >> On Apr 11, 2015, at 9:13 AM, Jack Davis <[email protected]> wrote: >> >> My wording problem. What I meant was focus at 1/3 of the distance into the >> scene, not at infinity. > > Can you judge the depth of field with that aperture at that distance? > > ------------------------------------------------------------------------------------------ > Eric Weir > Decatur, GA USA > [email protected] > > "Imagining the other is a powerful antidote to fanaticism and hatred." > > - Amos Oz > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
