On 10/19/2014 1:02 PM, Chuck Norcutt wrote:
Here's a little hyperfocal math at work showing the you can trust them numbers. The closest plants in this photo are
about 3 feet away from the camera. Note that "infinity" is in focus. Canon 5D, 24mm at f/11 with lens focused at 6
feet. This is actually a 2-image pano.
<http://www.chucknorcutt.com/Mt%20Rainier/pano%208552-8553er.htm>
Lovely @ 5x10" on my screen. But of course, being Pixel Peeper Moose, I kept
looking for where to click to embiggen it.
ALL DoF calculations and tables rely on assumptions about the CoC, as you know well. And they all have their roots in
opinion polls. Folks showed a bunch of prints to another bunch of folks, asked which were sharp and tallied the results.
That's why you set the viewing size in making the calculations.
Here's why I don't have and/or don't trust them numbers.
1. Right off the bat, I'm in trouble, because my 20/10 vision is an outlier; I don't have the same opinions about what
is sharp as the average.
2. The world has changed. We, at least the pixel peepers among us, routinely view images at magnifications never dreamed
of in film days (the movie Blowup not withstanding), if only because grain the size of golf balls isn't that interesting.*
I rather routinely take crops of rather small parts of an image and present them at 8.5x11" on my screen, larger or
smaller for various viewers on their screens.
Take the example I just used. Lets say I decide to do a gallery or book of the weather vanes I shot over the years.
(Farfetched for weather vanes, but two of my three books have come from images collected from over the years.) I have a
good shot of this one, in focus. I've added it to the existing comparison.
<http://www.moosemystic.net/Gallery/MPhotos/BayArea/Miscellaneous/AngelMoon.htm>
Had I used hyperfocal for 'good enough' focus, it would be soft at this size. Taken with the 14-150 @ 150. Had I had the
70-300 at the time, I wouldn't have needed such a crop, but that's part of the point: I didn't, but shot for the best
result, no matter what as yet unknown use I might put it to.
3. I said it before. My µ4/3 lenses don't have DoF markings, anyway, nor do any zooms I know of. This shot was taken
casually, when I parked in a tiny village and was about to walk to a store to pick up a custom order. How am I to make
all these calculations in any reasonable time frame? I don't even know for sure how far away the vane is.
I've tried using manual focus to find the middle between extremes, but the results have been mixed, at best. Usually to
my eye, not right for either end.
A couple of shots in a few seconds, and I'm done and on my way.
Directly On Focus Moose
* OK, another disclaimer, if only for me. Kodak made a special reversal film, originally for spy planes, I believe. We
used the commercial version back when. It seemed grainless and somehow like the subject ran out of detail before it did.
:-) Slow, very tricky to process, etc. As far as I know, no one was using it for regular photography. But for huge
enlargement on a rear projection screen, amazing.
--
What if the Hokey Pokey *IS* what it's all about?
--
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