Diffraction f/Entekaphobia

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Robin Casady
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Diffraction f/Entekaphobia
6 months ago

Interesting article on diffraction by Roger Cicala.

For those with f/entekaphobia (fear of f/11) it is interesting to note that f/11 was generally as sharp or sharper than f/4 and f/16 compared favorably to f/2.8. He tested with two Zeiss 50mm lenses and a Nikon 50mm f/1.4G.

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Peter Mueller
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Re: Diffraction f/Entekaphobia
In reply to Robin Casady, 6 months ago

Robin Casady wrote:

Interesting article on diffraction by Roger Cicala.

For those with f/entekaphobia (fear of f/11) it is interesting to note that f/11 was generally as sharp or sharper than f/4 and f/16 compared favorably to f/2.8. He tested with two Zeiss 50mm lenses and a Nikon 50mm f/1.4G.

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Robin Casady
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Thanks, Robin, this is interesting indeed and one learns about the cameras just as much as about the lenses.  I shoot quite a bit of macro and have often found that f/16 is not a problem, especially on lenses like the 200mm f/4 which seem optimized for the smaller openings.

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pluton
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Re: Diffraction f/Entekaphobia
In reply to Peter Mueller, 6 months ago

I have found that my Zeiss ZF lenses- particularly the 50/2,35/2, 28/2, and 21/2.8- have unusually good performance at f/11 and even f/16--even better on the D800 than my old D3.  The availability of sharpening only sweetens the pie.

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Leonard Shepherd
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Re: Diffraction and reality
In reply to Robin Casady, 6 months ago

The laws of optics have always said diffraction limited results are usually better at f16 than f1.4 to f4, and that if you increase the recording resolution (in Roger Circla's example D800 compared to D3s) resolution goes up even where diffraction reduces overall quality.

The results in the links confirm what the laws of optics predict

Perhaps more on this forum and elsewhere will now accept DSLR's do not break into pieces when used at smaller aperture settings

Indirectly referred to, if 600 lines (what Roger got with his set up) produces more resolution than the eye can resolve in a 16x12 inch print diffraction at f16 does not reduce image quality at all at this print size.

In a 10x8 print, diffraction at f22 and sometimes even f32 does not reduce image quality.

If further tesingt is done it is likely to confirm the diffraction effect is usually strongest with a wide angle lens, and reduced with a telephoto compared to the 50mm used in the comparison.

As a guide diffraction with a 300 mm prime does not become an overall resolution issue until about 1 stop smaller than with a 24 mm.

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CFynn
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Re: Diffraction and reality
In reply to Leonard Shepherd, 6 months ago

Leonard Shepherd wrote:

The laws of optics have always said diffraction limited results are usually better at f16 than f1.4 to f4, and that if you increase the recording resolution (in Roger Circla's example D800 compared to D3s) resolution goes up even where diffraction reduces overall quality.

The results in the links confirm what the laws of optics predict

Plenty of people seem happy to shoot with lenses wide open - yet reluctant to shoot at f/11 or f/16  because of diffraction. Yet their lenses are probably performing way better at f/11 or f/16 than they do wide open despite the effects of diffraction.

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bigpigbig
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Re: Diffraction and reality
In reply to Leonard Shepherd, 6 months ago

Leonard Shepherd wrote:

The laws of optics have always said diffraction limited results are usually better at f16 than f1.4 to f4,

I respect your knowledge, but I am confused.

Isn't this somewhat irrelevant?

I normally consider diffraction in deciding whether to shoot at f8, f11, f16 or f22. If diffraction is a concern, isn't usually because one is trying to gain depth of field by decreasing aperture?

Comparing the sharpness at f1.4, 2.0, 2.8 to f11, f16, and f22 seems pointless to me.

Can you explain why this comparison is important?

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rubank
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The real important lesson here
In reply to Robin Casady, 6 months ago

is that the D800 at f/16 produces more resolution than the D700 at any aperture.

When we get the next generation hi MP sensors (54 MP?) it will be even better.

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ormdig
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Re: Diffraction f/Entekaphobia
In reply to Robin Casady, 6 months ago

Thanks Robin, Roger is always a good read. He has that unique ability to look at things from a perspective that is 3 or 4 degrees "off kilter" than the rest of us,

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Bernard Delley
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Diffraction wideangle versu tele, laws of optics
In reply to Leonard Shepherd, 6 months ago

Leonard Shepherd wrote:

If further testing is done it is likely to confirm the diffraction effect is usually strongest with a wide angle lens, and reduced with a telephoto compared to the 50mm used in the comparison.

As a guide diffraction with a 300 mm prime does not become an overall resolution issue until about 1 stop smaller than with a 24 mm.

Interesting remarks. I could not relate to laws of optics I am aware of. Can you help?

I would know these 'laws':

in the diffraction limited regime of a lens (say f/16 f/22 ...) the Airy blur function on the sensor would depend just on this aperture ratio number, not on focal length.

;--) because of the magnification of the object with the long lens I can discern more details in the object. So I may be more oblivious to the blur. That would be more a psychological effect rather than optical.

on focus closer than infinity, the effective aperture ratio would change with the aperture diameter constant but the distance to the image plane increased to

f -->  f * ( 1 + rr )

where rr is the reduction ratio from object to image. So if rr is kept the same in the image (aunt Martha always filling the frame) the diffraction effect is the same irrespective of focal length.

for a long focal length lens with a tele design, there is an exit pupil effect. On close focus the exit  pupil acts a reduced aperture diameter producing a greater depth of field and greater diffraction blur diameter on the sensor.

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Humours Dip
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Re: Diffraction and reality
In reply to Leonard Shepherd, 6 months ago

Leonard Shepherd wrote:

The laws of optics have always said diffraction limited results are usually better at f16 than f1.4 to f4,

You could not be more wrong. The softness at wide apertures, especially F4, is due to aberrations other than diffraction e.g. spherical, chromatic, coma.

and that if you increase the recording resolution (in Roger Circla's example D800 compared to D3s) resolution goes up even where diffraction reduces overall quality.

The results in the links confirm what the laws of optics predict

Perhaps more on this forum and elsewhere will now accept DSLR's do not break into pieces when used at smaller aperture settings

Indirectly referred to, if 600 lines (what Roger got with his set up) produces more resolution than the eye can resolve in a 16x12 inch print diffraction at f16 does not reduce image quality at all at this print size.

In a 10x8 print, diffraction at f22 and sometimes even f32 does not reduce image quality.

If further tesingt is done it is likely to confirm the diffraction effect is usually strongest with a wide angle lens, and reduced with a telephoto compared to the 50mm used in the comparison.

As a guide diffraction with a 300 mm prime does not become an overall resolution issue until about 1 stop smaller than with a 24 mm.

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Leonard Shepherd
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olyflyer
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Re: The real important lesson here
In reply to rubank, 6 months ago

rubank wrote:

is that the D800 at f/16 produces more resolution than the D700 at any aperture.

No, not at ANY aperture... look at the charts again. Never the less, it is no surprise, the D800 has 3x the number of pixels on the same area, so of course it must produce higher resolution images with the same lens.

When we get the next generation hi MP sensors (54 MP?) it will be even better.

I think that camera would be even better, and that camera might produce higher resolution at any aperture compared with the D700.

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olyflyer
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Re: Diffraction and reality
In reply to CFynn, 6 months ago

CFynn wrote:

Leonard Shepherd wrote:

The laws of optics have always said diffraction limited results are usually better at f16 than f1.4 to f4, and that if you increase the recording resolution (in Roger Circla's example D800 compared to D3s) resolution goes up even where diffraction reduces overall quality.

The results in the links confirm what the laws of optics predict

Plenty of people seem happy to shoot with lenses wide open - yet reluctant to shoot at f/11 or f/16 because of diffraction. Yet their lenses are probably performing way better at f/11 or f/16 than they do wide open despite the effects of diffraction.

Exactly. I never really understood this "fear" of diffraction. Diffraction is there, but so what? If you need more DOF it is better to have the lens stopped down than not having enough DOF. Also, of course lenses are better at f/16 than at f/1.4, that's hardly revolutionary information for anyone who dared to use smaller than f/5.6 with the D800 or any other camera.

Diffraction is not like a concrete wall which you run into, it won't stop your camera from taking stunning images so I don't know why some people talk about it like if it was some kind of magic black hole which just prevents them from taking images.

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olyflyer
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Re: Diffraction f/Entekaphobia
In reply to Robin Casady, 6 months ago

Robin Casady wrote:

Interesting article on diffraction by Roger Cicala.

For those with f/entekaphobia (fear of f/11) it is interesting to note that f/11 was generally as sharp or sharper than f/4 and f/16 compared favorably to f/2.8. He tested with two Zeiss 50mm lenses and a Nikon 50mm f/1.4G.

I think those tests state the obvious. At least it is obvious to anyone who dare using smaller than f/5.6. Maybe f/5.6 is the most optimal in the majority of cases, but even that has been the obvious ever since I started with photography using SLRs in 1970.

Anyway, do you really think there are people who think a lens (any lens) can be better wide open than a bit stopped down? Is there really anyone who believes that lens would perform better wide open at f/1.4 or f/2.8 than stopped down to f/11 or f/16?

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Robin Casady
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Re: Diffraction f/Entekaphobia
In reply to olyflyer, 6 months ago

olyflyer wrote:

Robin Casady wrote:

Interesting article on diffraction by Roger Cicala.

For those with f/entekaphobia (fear of f/11) it is interesting to note that f/11 was generally as sharp or sharper than f/4 and f/16 compared favorably to f/2.8. He tested with two Zeiss 50mm lenses and a Nikon 50mm f/1.4G.

I think those tests state the obvious. At least it is obvious to anyone who dare using smaller than f/5.6. Maybe f/5.6 is the most optimal in the majority of cases, but even that has been the obvious ever since I started with photography using SLRs in 1970.

Anyway, do you really think there are people who think a lens (any lens) can be better wide open than a bit stopped down? Is there really anyone who believes that lens would perform better wide open at f/1.4 or f/2.8 than stopped down to f/11 or f/16?

From past threads on diffraction I think there are people who are comfortable shooting at f/1.4 to f/2.8 but have entekaphobia. Roger is a self-admitted entekaphobe.

Personally, I've been hesitant to shoot at f/16, but then I am hesitant to shoot at f/4 and wider as well.

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Robin Casady
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Re: The real important lesson here
In reply to olyflyer, 6 months ago

olyflyer wrote:

rubank wrote:

is that the D800 at f/16 produces more resolution than the D700 at any aperture.

No, not at ANY aperture... look at the charts again. Never the less, it is no surprise, the D800 has 3x the number of pixels on the same area, so of course it must produce higher resolution images with the same lens.

Nikon 50mm f/1.4 on D700 highest res looks to be almost 750 center and almost 650 corner at f/8. On the D800 @ f/16 it appears to be around 825 center and 700 corner. So, if you compare center to center or corner to corner then rubank is correct. The D700 center is only slightly ahead of the D800 f/16 corner.

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olyflyer
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Re: The real important lesson here
In reply to Robin Casady, 6 months ago

Robin Casady wrote:

olyflyer wrote:

rubank wrote:

is that the D800 at f/16 produces more resolution than the D700 at any aperture.

No, not at ANY aperture... look at the charts again. Never the less, it is no surprise, the D800 has 3x the number of pixels on the same area, so of course it must produce higher resolution images with the same lens.

Nikon 50mm f/1.4 on D700 highest res looks to be almost 750 center and almost 650 corner at f/8. On the D800 @ f/16 it appears to be around 825 center and 700 corner. So, if you compare center to center or corner to corner then rubank is correct. The D700 center is only slightly ahead of the D800 f/16 corner.

Yes, you are right.

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coronawithlime
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Re: Diffraction f/Entekaphobia
In reply to Robin Casady, 6 months ago

I find this an extremely interesting article in view of the fact I can't remember the last time I shot at f11. Not for any particular reason, just what I had been taught.

Regarding Rogers maps, as I look at my current Texas map (my home), everything north of the Red River is labeled "Here there be Daemons",  illustrated by something that looks suspiciously like a University of Oklahoma football player.

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JWReagan
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Re: Diffraction f/Entekaphobia
In reply to Robin Casady, 6 months ago

I don't think i have ever concerned myself with softness from shooting wide open or stopped way down. If I do either one of those things it's because I need to in order to get the shot I want. Image sharpness is pretty insignificant compared the other aspects of making a great photo... I can't recall ever being captivated by an image because of its corner to corner sharpness.

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RomanJohnston
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I even shoot F/22 at times
In reply to Robin Casady, 6 months ago

Its all about tradeoffs. I wold sometimes rather have a slightly diffracted but generally sharp picture and use F/22 than F/8 and stack photos or have a long drawn out post processing issues.

I still try to stick closer to f/8 when the shot allows, but not afraid to break that ceiling when needed.

Becoming less of an atom splitter, and remembering that  compelling shot well taken can be forgiven some hair splitting detail loss to make sure I capture the essence of the shot. Only other photographers will nit pick the details to death and ignore the essence and beauty of the shot.

And those are not my target market. I rarely get a sale from other photographers.

Roman

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Lasse Eisele
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Hogwash
In reply to Leonard Shepherd, 6 months ago

Leonard Shepherd wrote:

The laws of optics have always said diffraction limited results are usually better at f16 than f1.4 to f4, and that if you increase the recording resolution (in Roger Circla's example D800 compared to D3s) resolution goes up even where diffraction reduces overall quality.

Nonsense. The softness at wider apertures has nothing to do with "the laws of optics". It is caused by lens aberrations and can be overcome with better designs and better glass. A (hypothetical) perfect lens will always be sharpest wide open, ie it will be diffraction limited wide open.

Some of the exotic tele lenses, like the 200/2 or 300/2.8, are actually not that far away from perfection. They are very close to peak performance wide open.

The results in the links confirm what the laws of optics predict

Absolutely not. The results confirm that the tested lenses could be designed better.

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