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Sharpest Aperture?!
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May 30, 2016 11:21:19   #
folkus
 
When I Googled "Sharpest Aperture" I found Ken Rockwell's discussion ("How to Select the Sharpest Aperture"). It seems to fly in the face of what I have heard in the past and wondered if I had stumbled on a neat photography improvement for my photo adventures or was it "out to lunch". I know a bunch of you hard and grizzled UHHers will tell me to go try it and find out for myself - quit being lazy, Folkus, you'll say. BUT. there may be others that would like to engage in the subject. His article speaks to Nikon, Canon, Leica, and Pentax users so I thought there might be an interested audience. He gives many examples but the one that struck me was where the lens DOF scale says use F/8, he says F/13 gives the optimum sharpness. All discussions are welcome, but I suggest that you read the article before you challenge it to vehemently. Come on - - let's play.

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May 30, 2016 11:45:36   #
Screamin Scott Loc: Marshfield Wi, Baltimore Md, now Dallas Ga
 
Diffraction robs sharpness at F13 as opposed to F8, especially on a crop sensor camera.

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May 30, 2016 12:02:18   #
joer Loc: Colorado/Illinois
 
Screamin Scott wrote:
Diffraction robs sharpness at F13 as opposed to F8, especially on a crop sensor camera.


It depends on the lens, sensors size and so many other factors. There is no global sharpest f-stop.

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May 30, 2016 12:22:09   #
Screamin Scott Loc: Marshfield Wi, Baltimore Md, now Dallas Ga
 
That is true....
joer wrote:
It depends on the lens, sensors size and so many other factors. There is no global sharpest f-stop.

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May 30, 2016 12:27:24   #
jcboy3
 
Most lenses are sharpest when stopped down 1-2 stops from maximum aperture, but a few are actually sharpest at maximum aperture (those are usually not the fastest lenses). But this is with respect to the focus distance.

Rockwell's point is that, when looking for sharpness over a particular DOF, the minimum aperture is defined to achieve focus assuming a particular print size and viewing distance. And this depends as well upon the sensor size and resolution, which determine the value of the "circle of confusion", which is then used to compute DOF. But that's just a minimum, and if you stop the lens down, you will enlarge the DOF and achieve sharper results over the desired DOF. Until you stop down too much, and diffraction starts reducing sharpness.

The rule of thumb I use is to set the aperture 1-2 stops above what's required for the desired DOF, but not more than halfway to the diffraction limit. On full frame, that's f/16-f/22. On crop sensor, it's whatever the crop factor is times the aperture.

This only works, however, if all you care about is sharpness. If part of your goal is to blur the background, then you should use wider apertures and set focus ahead of your subject.

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May 30, 2016 12:36:29   #
anotherview Loc: California
 
While so, the physical phenomenon of diffraction introduces a growing blurring of images as the aperture narrows from an aperture more in the middle of the aperture range -- typically at f/7.1 to f/8, at least for modern DSLRs.

I understand master photographers like Ansel Adams shot an aperture of f/64 to maximize image sharpness. Maybe this difference has something to do with the medium, one film and the other a sensor.

I expect the knowledgeable ones here will elaborate on this topic to enlighten the rest of us.
joer wrote:
It depends on the lens, sensors size and so many other factors. There is no global sharpest f-stop.

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May 30, 2016 13:28:23   #
jcboy3
 
anotherview wrote:
While so, the physical phenomenon of diffraction introduces a growing blurring of images as the aperture narrows from an aperture more in the middle of the aperture range -- typically at f/7.1 to f/8, at least for modern DSLRs.

I understand master photographers like Ansel Adams shot an aperture of f/64 to maximize image sharpness. Maybe this difference has something to do with the medium, one film and the other a sensor.

I expect the knowledgeable ones here will elaborate on this topic to enlighten the rest of us.
While so, the physical phenomenon of diffraction i... (show quote)


Ansel Adams shot medium and large format; with correspondingly smaller apertures required to achieve similar DOF.

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May 30, 2016 14:17:54   #
Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)
 
folkus wrote:
When I Googled "Sharpest Aperture" I found Ken Rockwell's discussion ("How to Select the Sharpest Aperture"). It seems to fly in the face of what I have heard in the past and wondered if I had stumbled on a neat photography improvement for my photo adventures or was it "out to lunch". I know a bunch of you hard and grizzled UHHers will tell me to go try it and find out for myself - quit being lazy, Folkus, you'll say. BUT. there may be others that would like to engage in the subject. His article speaks to Nikon, Canon, Leica, and Pentax users so I thought there might be an interested audience. He gives many examples but the one that struck me was where the lens DOF scale says use F/8, he says F/13 gives the optimum sharpness. All discussions are welcome, but I suggest that you read the article before you challenge it to vehemently. Come on - - let's play.
When I Googled "Sharpest Aperture" I fou... (show quote)


Each lens is different, and some, like long telephoto lenses are sharpest at max aperture - F2.8 or F4 and will suffer a bit stopped down even one stop. Others, particularly fast 1.2, 1.4 and 1.8 lenses often have good center sharpness, and corner/edges that are soft until stopped down to F5.6 or F8. With today's high density sensors, full frame cameras at 24-36 mp already begin to show loss of sharpness from diffration at F8, while M4/3 and smaller sensor cameras show diffraction effects at F5.6.

There is no magic, one-size-fits-all general rule - each lens is different. Only the loss of sharpness due to diffraction is a universal phenomenon.

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May 30, 2016 14:33:29   #
jcboy3
 
Gene51 wrote:
Each lens is different, and some, like long telephoto lenses are sharpest at max aperture - F2.8 or F4 and will suffer a bit stopped down even one stop. Others, particularly fast 1.2, 1.4 and 1.8 lenses often have good center sharpness, and corner/edges that are soft until stopped down to F5.6 or F8. With today's high density sensors, full frame cameras at 24-36 mp already begin to show loss of sharpness from diffration at F8, while M4/3 and smaller sensor cameras show diffraction effects at F5.6.

There is no magic, one-size-fits-all general rule - each lens is different. Only the loss of sharpness due to diffraction is a universal phenomenon.
Each lens is different, and some, like long teleph... (show quote)


Gene, you missed the point. This was not about sharpness at focus, but sharpness over a wide DOF. The point being that for a given DOF, the suggested aperture is the minimum for acceptable focus. The sharpness will improve as you stop down, until the effects of diffraction outweigh the increased DOF.

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May 30, 2016 14:42:59   #
mwsilvers Loc: Central New Jersey
 
folkus wrote:
When I Googled "Sharpest Aperture" I found Ken Rockwell's discussion ("How to Select the Sharpest Aperture"). It seems to fly in the face of what I have heard in the past and wondered if I had stumbled on a neat photography improvement for my photo adventures or was it "out to lunch". I know a bunch of you hard and grizzled UHHers will tell me to go try it and find out for myself - quit being lazy, Folkus, you'll say. BUT. there may be others that would like to engage in the subject. His article speaks to Nikon, Canon, Leica, and Pentax users so I thought there might be an interested audience. He gives many examples but the one that struck me was where the lens DOF scale says use F/8, he says F/13 gives the optimum sharpness. All discussions are welcome, but I suggest that you read the article before you challenge it to vehemently. Come on - - let's play.
When I Googled "Sharpest Aperture" I fou... (show quote)

As a very general "rule" the sharpest aperture is often, but far from always, around 2 stops down from wide open. For a 35mm f/1.4 prime, for instance, that would mean the sharpest aperture may be around f/2.8. I repeat, it is NOT a hard and fast rule, more of a guideline. If you are talking about sharpness throughout the image with a wide DoF, that's a different issue. While f/11 or f/13 may be great to get everything in focus, the lens is not necessarily at its sharpest. An aperture where "everything" is in focus, versus the "sharpest" aperture are not necessarily the same thing.

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May 30, 2016 14:45:24   #
jcboy3
 
mwsilvers wrote:
As a very general "rule" the sharpest aperture is often, but far from always, around 2 stops down from wide open. For a 35mm f/1.4 prime, for instance, that would mean the sharpest aperture may be around f/2.8. I repeat, it is NOT a hard and fast rule, more of a guideline.


Another miss.

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May 30, 2016 14:48:56   #
mwsilvers Loc: Central New Jersey
 
jcboy3 wrote:
Another miss.

I edited my comment. Take another look.

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May 30, 2016 14:49:18   #
Bill_de Loc: US
 
From the article:

"This article is written for the virtuoso large format photographic artist.

If you are a beginner or just shooting a 35mm or digital camera then this article addresses issues which won't bother you at reasonable apertures. Just use a tripod and choose the smallest aperture you have if you need depth of field. Avoid apertures smaller than f/8 or f/11 on digital cameras."

--

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May 30, 2016 16:40:51   #
folkus
 
Bill de - are you ducking valuable "truths" whether a novice, good amateur, or experienced professional? Is there something of worth for all levels - whether a beginner or not?

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May 30, 2016 16:56:02   #
Bill_de Loc: US
 
folkus wrote:
Bill de - are you ducking valuable "truths" whether a novice, good amateur, or experienced professional? Is there something of worth for all levels - whether a beginner or not?


I'm quoting the author, those are not my words.

--

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