Diffraction limited performance

trendland · Apr 12, 2019

Dan Fromm said:
Hmm. So if I hang a 35 mm Nikon behind my 610/9 Apo-Nikkor and stop the lens all the way down to f/128 (as far as it goes) I'll be able to get a good 8x10 print?

This seems impossible. At f/128, the diffraction limit is approximately 1500/128 = 12. So I'll have 12 lp/mm at low contrast on my 24x36 piece of film. Enlarged 8x to make an 8x12 print that crops to 8x10, I'll have 1.5 lp/mm at low contrast in the print. Fuzzy, fuzzy.

I am not realy sure if the 3mm roule is for old type lenses (like sunny 8 is for old type films from lower speed) I am also not very sure about if it is gerneral = for 35mm and 120 medium format and 4x5 and for 8x10??? I doubt a bit on that friends!

Is it indeed up to date to modern lenses of APO type? From my point a general rule might work fine up to a certain point but can't work without exeptions! Because DEFRACTION is also in regard of lens design!
Because DEFRACTION can higher optical failures! But perhaps I made a misstake at indeed this point?
Never mind because Ian Grant gave a good advice : TRY AND ERROR!

With Regards

trendland · Apr 12, 2019

M. Axel Wikstrom said:
I think diffraction is where digital photography will soon hit a wall no matter how perfect the lenses become - at least in the smaller formats.

Do I understand you correct that digital photography will soon reach physically restrictions?

with regards

PS I'll be waiting for this.....!
PS : I speculated about a bariere for 35 mm digital at 30MP , later at 45MP, later at 60MP...a.s.o! But here - this old fashioned 3mm rule has its chance!

Dan Fromm · Apr 12, 2019

Trendland, there's something about discussions of diffraction that makes many of us go all mystical.

The diffraction limit is approximately 1500/(effective f#) lp/mm at low contrast. For example, for f/128, 1500/128. This is independent of format and lens' focal length.

Effective f# depends on the f# set and on magnification, is f# set * (magnification + 1). So, for example, at 1:1 (magnification = 1) and f/16 set the effective f# is 32 and the diffraction limit is 1500/32 = 46. This is why I can't make decent 8x10 prints from my Kodachromes (KM, thank you) shot at 1:1 at f/16 set.

Dali · Apr 12, 2019

Dan, isn't diffraction inherent to the physical nature of light, related to the real aperture of an optical device and independant from any optical design?

trendland · Apr 12, 2019

Dan Fromm said:
Trendland, there's something about discussions of diffraction that makes many of us go all mystical.

The diffraction limit is approximately 1500/(effective f#) lp/mm at low contrast. For example, for f/128, 1500/128. This is independent of format and lens' focal length.

Effective f# depends on the f# set and on magnification, is f# set * (magnification + 1). So, for example, at 1:1 (magnification = 1) and f/16 set the effective f# is 32 and the diffraction limit is 1500/32 = 46. This is why I can't make decent 8x10 prints from my Kodachromes (KM, thank you) shot at 1:1 at f/16 set.

Simular thoughts to me : It is different to 35mm/120 medium format/a.s.o!
Thanks Dan!

with regards

PS :

trendland · Apr 12, 2019

Dali said:
Dan, isn't diffraction inherent to the physical nature of light, related to the real aperture of an optical device and independant from any optical design?

Yes of course there is a concern in regards of "wafe length" !
with regards

M. Axel Wikstrom · Apr 12, 2019

Once you hit the diffraction limit, the only way to go sharper is to go bigger with the format. A diffraction limit encountered at let's say f/2, would result in an extremely sharp photo with 24x36mm format, but at the cost of depth of field (very few lenses, if any, are this good). Of course when we stop down to gain depth of field is when diffraction becomes more and more of an issue, and where the only way to go is up in format.

M. Axel Wikstrom · Apr 12, 2019

Here's a fairly straightforward discussion on diffraction:

https://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

trendland · Apr 12, 2019

Dan Fromm said:
Trendland, there's something about discussions of diffraction that makes many of us go all mystical.

The diffraction limit is approximately 1500/(effective f#) lp/mm at low contrast. For example, for f/128, 1500/128. This is independent of format and lens' focal length.

Effective f# depends on the f# set and on magnification, is f# set * (magnification + 1). So, for example, at 1:1 (magnification = 1) and f/16 set the effective f# is 32 and the diffraction limit is 1500/32 = 46. This is why I can't make decent 8x10 prints from my Kodachromes (KM, thank you) shot at 1:1 at f/16 set.

Ähmm misunderstand your post #28 a little = sorry Dan.....it is AS you said "independent"
of Format! Well never the less : " Trendland " gets out of the discussion at this point because of higher math see :

"Bessels" differential equation 2nd order :

next is "Bessel operator" = (differential operator 2nd order) see :

Next is looking real easy (if one is able to follow step 1 and step 2)

see :

But this isn't enough.....

see:

easy going again (but just regarding principle of our well known aperature in concern of
wafes) see (easy model) :

soon we are confronted again ! Ähmm from what??? "Defraction Integral"

see:

=

and here we have it (remember #23)=DEFRACTION WILL PROCEED IN FORM OF A LOG FUNCTION :

At last YouTube can help :

with regards

PS : Don't press the YouTube boton, save your time = look what Ian stated : Try and error!

MattKing · Apr 12, 2019

Dan Fromm said:
Hmm. So if I hang a 35 mm Nikon behind my 610/9 Apo-Nikkor and stop the lens all the way down to f/128 (as far as it goes) I'll be able to get a good 8x10 print?

This seems impossible. At f/128, the diffraction limit is approximately 1500/128 = 12. So I'll have 12 lp/mm at low contrast on my 24x36 piece of film. Enlarged 8x to make an 8x12 print that crops to 8x10, I'll have 1.2 lp/mm at low contrast in the print. Fuzzy, fuzzy.

Reconsider y'r rule of thumb. It seems absurd.

Might work for contact printing an 8x10 negative, except for the low contrast.

Dan,
It seems to me that the "rule of thumb" factors in the magnification required to print to the desired print size, and assumes a full frame print.
Not all that different from lens quality considerations in general.

Ian Grant · Apr 12, 2019

M. Axel Wikstrom said:
Here's a fairly straightforward discussion on diffraction:

https://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

I'm not sure the calculator at the bottom is up to much as it doesn't take into account Focal lenght.

If I assume a 150mm lens on my 5x4 cameras it's saying there's no difraction limitation at f64. Now my late producyion 150mm f5.6 Xenar is marked to f64, quite why I'm not sure - it is the original shutter and scalem but then my 150mm f5.6 Sironar N is alsi marked to f64, a 150mm f4.5 Xenar and Carl Zeiss 150mm f4.5 Tessar (not CZJ) are only marked to f32. If we assume the 3mm rule Maris mentions then f45 fits the bill.

A question though is does design affect the issue particularly with wide angle lenses ?

Ian

trendland · Apr 12, 2019

MattKing said:
Dan,
It seems to me that the "rule of thumb" factors in the magnification required to print to the desired print size, and assumes a full frame print.
Not all that different from lens quality considerations in general.

That is the point "Trendland" is back again - thanks MattKing!
Yes of course : The rule of thumb is basis for me to look at defraction parameters also in regards of lens design!

with greeting

M. Axel Wikstrom · Apr 12, 2019

Ian Grant said:
I'm not sure the calculator at the bottom is up to much as it doesn't take into account Focal lenght.

If I assume a 150mm lens on my 5x4 cameras it's saying there's no difraction limitation at f64. Now my late producyion 150mm f5.6 Xenar is marked to f64, quite why I'm not sure - it is the original shutter and scalem but then my 150mm f5.6 Sironar N is alsi marked to f64, a 150mm f4.5 Xenar and Carl Zeiss 150mm f4.5 Tessar (not CZJ) are only marked to f32. If we assume the 3mm rule Maris mentions then f45 fits the bill.

A question though is does design affect the issue particularly with wide angle lenses ?

Ian

A shorter lens will have more diffraction due to its smaller aperture opening for a given aperture value, but since the film format is larger, in practical terms it won't be seen due to not having to enlarge as much. Diffraction may never be visible with most large format lenses anyway because size matters - unless the enlargement is very big. An optical design projecting 50 lp/mm onto a 4x5 sheet of film will result in a sharper image than an optic projecting 100 lp/mm onto 24x36mm, and may never intersect a diffraction limit at its smallest aperture.

Sirius Glass · Apr 12, 2019

I appreciate and enjoy the mathematics and equations, but for those that do not or are getting lost the hyperfocus sweet spot and defraction limits are roughly

Format ___ Sweet Spot___Defraction Limit
35mm _____ f/8 ______ f/16
120 ________ f/11 _____ f/22
4"x5" ______ f/16 _____ f/32
5"x7" ______ f/22 _____ f/45
8"x10" _____ f/32 _____ f/90

trendland · Apr 12, 2019

Sirius Glass said:
I appreciate and enjoy the mathematics and equations, but for those that do not or are getting lost the hyperfocus sweet spot and defraction limits are roughly

Format ___ Sweet Spot___Defraction Limit
35mm _____ f/8 ______ f/16
120 ________ f/11 _____ f/22
4"x5" ______ f/16 _____ f/32
5"x7" ______ f/22 _____ f/45
8"x10" _____ f/32 _____ f/90

That's what I would call "extreme roughly" sorry Sirious glass but Ii guess it would not more help than to state ISO 100 is more speed in comparision of ISO 50 but ISO 800 is "quite more speed"
[roughly].....

just regarding your table for 35mm = a normal lens roughly have defraction limit at f16 concerning
a 35mm zoom (oldfashioned) f 5.6 - 6.3 there you normaly perhaps not find f22 in a scale but of you may notice it that concern is obviously to a higher priced f 6.0 lens defraction limit f22?
Same is with a Zeiss 35mm APO = Sweetspot f8?? Oh no where is my money I want it back!!
But roughly you are right - Sirious Glass - "Somewhere" around your table listed!

with regards

PS : It is like the beginning of some movies with Bruce Willis! The opening scene showing a ship USS Harry S. Truman "somewhere in the Indian Ocean"

Dan Fromm · Apr 12, 2019

M. Axel Wikstrom said:
A shorter lens will have more diffraction due to its smaller aperture opening for a given aperture value.

Why do you believe this?

trendland · Apr 12, 2019

Thats my point SeriousGlass :

Just regarding 35mm [resolution in concern] we should regards sweetspot, optical characteristics,
AND defraction = parameters in concern of "limiting performance!

35mm____f/4.0-11__f/8-22
think about resolution in concern of rule of thumb factors!

with regards

PS : concerning sweetspot - examples :Zeiss 35mm f1.2 (sweetspot near 4.0)
,...,........................................................: Tokina 80-170 f/5,3- 6,9 (1979) (sweetspot near11)!

Nodda Duma · Apr 12, 2019

Dali said:
Dan, isn't diffraction inherent to the physical nature of light, related to the real aperture of an optical device and independant from any optical design?

Since the aperture is a part of the optical design, no it is not independent via the dependency of diffraction on f/#.

Nodda Duma · Apr 12, 2019

M. Axel Wikstrom said:
A shorter lens will have more diffraction due to its smaller aperture opening for a given aperture value, but since the film format is larger, in practical terms it won't be seen due to not having to enlarge as much. Diffraction may never be visible with most large format lenses anyway because size matters - unless the enlargement is very big. An optical design projecting 50 lp/mm onto a 4x5 sheet of film will result in a sharper image than an optic projecting 100 lp/mm onto 24x36mm, and may never intersect a diffraction limit at its smallest aperture.

Not correct. The magnitude of the diffraction is dependent on the f/#, not the aperture diameter.

Nodda Duma · Apr 12, 2019

Btw, recall listening to a radio station fading in and out as you drove away from it? That’s diffraction of the radio frequency. It reminds us that we can and should treat photons as waves as well as rays/particles.

M. Axel Wikstrom · Apr 12, 2019

It is dependent on aperture diameter, but since longer lenses produce a larger image on the film it is canceled out by the focal length. Maybe I should have been more clear.

Radio fading is typically caused by multi-path influences such as reflections from buildings, terrain, and indirect signal path. On lower frequencies using ionospheric propagation over long distances it's also caused by variations of the minimum useable frequency (MUF). Diffraction can be part of it, but a small part.

Dali · Apr 12, 2019

Nodda Duma said:
Since the aperture is a part of the optical design, no it is not independent via the dependency of diffraction on f/#.

OK but for a similar aperture, does the optical design have an impact? Said differently, does a Sonnar 50 mm @ F/16 diffracts more or less than a Tessar 50mm at the same relative aperture?

Nodda Duma · Apr 12, 2019

The aperture is part of the optical design. It’s not just a random piece of the barrel, but impacts aberrations, performance and, of course, the amount of light that reaches the image plane.

To be absolutely correct, the Working f/# is used to calculate the Airy disc diameter, and the specific spectral transmission of the optics should be factored in to the integrated wavelength. The working f/# factors in exit pupil magnification (the cause of bellows factor) and of course is different fir different designs. In addition, aberrations at f/16 are different for different designs and will affect the actual shape of the Airy disc (which convolves with the scene to cause diffractive blurring). So the answer is ... the full optical design including the aperture must be considered to begin predicting diffractive effects with any accuracy. Not really an exercise for the photographer, though.

M. Axel Wikstrom said:
It is dependent on aperture diameter, but since longer lenses produce a larger image on the film it is canceled out by the focal length. Maybe I should have been more clear.

Radio fading is typically caused by multi-path influences such as reflections from buildings, terrain, and indirect signal path. On lower frequencies using ionospheric propagation over long distances it's also caused by variations of the minimum useable frequency (MUF). Diffraction can be part of it, but a small part.

You found a different way of saying that diffraction is dependent on f/#. It takes some thought to understand the relationship between f/#, aperture, and focal length beyond the mere mathematical equation. It took a while for me, too, and I went through a phase of envisioning it as you are. Once the puzzles come together, however, you’ll get it and move on.

Diffraction is a significant effect for radio fading in and out at the limits of the range (what I implied but could have been clearer on). This is well-documented, and is separate and distinct from the other phenomena you list.

RalphLambrecht · Apr 13, 2019

trendland said:
In general (guess you'll know ) a lens at "max open aperature" let's say at 2.0 will normally have a real profit (more resolution in lines per mm/or MTF) from "closing" the lens 2.8, 4 , 5,6 , a.s.o.!
EXEPTION : very good and max. corrected AND real expensive lenses from type Leica and others
(guess most modern Hassi lenses you also can count to that types)!
There you can reach max. resolution with max. open lens! But it is dependable!
In all cases (from my point) you can higher the performance a little bit example :
Zeiss lens at about 1.2 has extreme resolution but at 1.4 you can maximal it a bit ~ 9,5% and with 2.0 again 3,5 % and this is it (at 4.0 the profit in direction of better characteristics isn't real messurable (+ 0,967 for example) but it is enought to define then the sweetspot for this lens at 4.0 = best characteristcs you can get with this lens!
What will happen with this Zeiss (it is just an example to make clear the general mechanism - so be aware of to unterstand the mentioned datas precise) - what will happen with the Zeiss at 5.6?
In best case you will have identical characteristics (no messurable difference) in fact (in reality) you will louse a bit of resolution (lets say 0,856%) - because of what mechanism?
Because of DEFRACTION at 5.6 ! REALY ? Yes realy (because the definied sweetspot is INDEED at
4.0) What will happen at f8 ? AND NOW LISTEN IT IS NOT SO MUCH COMPLICATE TO UNDERSTAND BUT HERE IS THE CENTRAL KEY TO YOUR QUESTION :
THE DEFRACTION WILL PROCEED IN A FORM OF A LOG. FUNCTION!!!!
So at f8 you can louse - 3,9% resolution, f11 - 5,9%, f 16 - 12,2 % f22 - 31% f32 - 49% f 45 -68%!
If your lens has no good characteristics your sweetspot can be just at 5,6 a bad lens from old type may have it at f8! But a bad lens may have a higher log witthin DEFRACTION (from my point)!
With Zeiss for Hassi it will not be the last mentioned case = no bad lenses at all!
I noticed real unsharpness at f22 and wonder about (many years ago) and that was
DEFRACTION - NOTHING ELSE!
THE NEXT PARAMETER TO DISCUSS (IT WOULD HELP YOU NOT VERY MUCH FOR YOUR WORKFLOW IN CONCERN OF DEEP OF FIELD SHARPNESS) WOULD BE : HYPERFOCAL DISTANCE!

with regards

simpler put,every lens has a 'sweetspot'(optimum optiocal performance);wide open,the lens is limited by abberations;stopped down, it is limited by diffraction.The sweetspot is when it's closed down sufficiently to control abberations but not too far to give diffraction a chance have a negative effect.stopping down a couple of stops from wide open typically does t5he trick.

trendland · Apr 13, 2019

RalphLambrecht said:
simpler put,every lens has a 'sweetspot'(optimum optiocal performance);wide open,the lens is limited by abberations;stopped down, it is limited by diffraction.The sweetspot is when it's closed down sufficiently to control abberations but not too far to give diffraction a chance have a negative effect.stopping down a couple of stops from wide open typically does t5he trick.

Ralph - this issue here seams indeed not to be such easy to understand ( looking just at how this discussion proceed.....) - therefore my final aproach (I mentioned) is in regard what Ian stated
(try and error)! In general it is NO BAD THING if each photograhers have own thoughs of how defraction is working and what the impact for resolution a.s.o. is for the practice!
Some may be right - some others here may be wrong (me too I am NOT 100% sure about -
but to 87,235%!)
What you stated Ralf in concern of different Sweet Spots (each lens has OF COURSE its individual Sweet Spot - and many lenses of the same period and comparable design/characteristics have it
at the same f/5.6 but there is no rule ) is right - so I agree with you!
It is a theme from highest complexity - but let me state : The issue that their is a Sweet -Spot at a definied f-stop /aperature to each lens (for example at f5.6 - lets state it for one XY lens)
AND the issue that resolution is coming down (at f/8...behind that Sweet Spot ) is what I would call an indirect prove that there is beginning a defraction ! Sorry that has some of my logic here! But I might be wrong! The procedure of defraction seams indeed to beginn with lowest value coming to f11.....f16...…there it became a problem (visual lost of resolution)!
By the way : I realy didn't care about defraction - till I noticed it at f22....!
GLAD ABOUT THAT WE ALL ARE PHOTOGRAPHERS AND NOT HAVE TO BE LENS DESIGN EXPERTS!

with regards

PS : Because therefore (to be expert for design lenses) we would have to be experts from highest reputation (at real high level) in 3 main qualifications!
The first would be math, the second would be......? MATH....the 3. MATH!

Diffraction limited performance

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