Lens diffraction - truth or urban legend?

Sparrow said:
Well yes that's the point, diffraction is such a minor effect it cannot be considered the "weakest link" and it would be a waste of time for anyone new to photography to give it any thought at all ... which is pretty much the answer to the OP's question would you agree? 🙂
Click to expand...

Yes, of course. I said that at the beginning of this thread, and again this morning.

Just speaking for myself, I've been a pro/advance-amateur photographer since the 1980's. Except for scientific photography I've never had a situation where lens diffraction might have been a concern... let alone a problem.

... and I shoot film


... and I have had just as many fuzzy phots coming out of a digital workflow


... and I worry about lots of things, but try to worry about only things that are worh worrying about


... and lens diffractionis not one of them... based on lots of experience!
 
Gumby said:
Yes, of course. I said that at the beginning of this thread, and again this morning.

Just speaking for myself, I've been a pro/advance-amateur photographer since the 1980's. Except for scientific photography I've never had a situation where lens diffraction might have been a concern... let alone a problem.

... and I shoot film


... and I have had just as many fuzzy phots coming out of a digital workflow


... and I worry about lots of things, but try to worry about only things that are worh worrying about


... and lens diffractionis not one of them... based on lots of experience!
Click to expand...

I started in 1964, learned of diffraction in college and have yet to see it in the wild ... I too can take a fuzzy photo without it's involvement
 
Sparrow said:
... and of course you will be supporting those assertions with photos no doubt?
Click to expand...

Nope. But I've done the tests years ago and verified for myself that there is a very noticeable difference when you get it right. That is, I could see the difference in the prints.

Antenna? They blow about in the wind don't they? Even in a tiny breeze and on a bright sunny day houses create thermals which are popping off constantly and thermals are very turbulent so don't tell me there was no wind because you can't see thermals which are not depandant on wind. Just so its clear, the attenna is not a good example and I'm not saying those results are wrong but rather making it clear to you that one test proves nothing and just because you haven't observed the effects of diffraction doesn't mean others who have done more stringent test haven't either or that the effect doesn't exist. It's simple physics but that is just theory. In the real world you have to do tests and the tests I did showed diffraction was an observable effect for the lenses I tested.
 
tlitody said:
Nope. But I've done the tests years ago and verified for myself that there is a very noticeable difference when you get it right. That is, I could see the difference in the prints.

Antenna? They blow about in the wind don't they? Even in a tiny breeze and on a bright sunny day houses create thermals which are popping off constantly and thermals are very turbulent so don't tell me there was no wind because you can't see thermals which are not depandant on wind. Just so its clear, the attenna is not a good example and I'm not saying those results are wrong but rather making it clear to you that one test proves nothing and just because you haven't observed the effects of diffraction doesn't mean others who have done more stringent test haven't either or that the effect doesn't exist. It's simple physics but that is just theory. In the real world you have to do tests and the tests I did showed diffraction was an observable effect for the lenses I tested.
Click to expand...

No wind. Antenna's variation in sharpness is gradual stop after stop. f/8 and f/11 are in general sharper than f/4 and f/5.6.

Cheers,

Juan
 
And another thing. Increasing sharpness at smaller apertures can indicate a poor quality lens. My zeiss lenses perform best at f5.6 to f8 at my typical taking distances. Does that mean Leica lenses aren't as good as people like to beleive? Well maybe or maybe not. It depends on your criteria for good. It also depends on where the lens is designed to perform best. Closish or distant. My guess is that Leica lenses are optimised for closish and not infinity so distant subjects like the antenna are not IMO where they will perform best. Another reason why the antenna test may not be a good example. That is to say that if a lens' optical performance is best at closih ditances, you may have to close down more to get distant subjects sharp. So Antenna test proves nothing. And as always, since no one does tests to find the optimum distance for optimum lens performance, using any distance is subject to question. i.e. lens tests outside of the laboratory are always subject to question big time. All you can do is your own tests at typical taking distances and find out how that lens performs at that distance. You CAN NOT say those results apply across the board to the effects of diffraction since the smallness of the aperture may be required to get rid of lens abberations at greater distances.
 
Diffraction is real, but it's effects on a real photograph taken with lenses made for photography is small.

It's easy to show the effects are real using a Laboratory setup. Classic Freshman Physics.

Showing these effects in a real-world scenerio using consumer grade equipment is not easy, indicating the effects are small. The jitter and motion of the test target introduced using long exposure times are likely to knock the effects of diffraction into the noise. Offsetting long exposure times using fast film and high-ISO are also going to knock the effects of diffraction into the noise.

So- I would not worry too much about it. If you need DOF, stop down. If you don't, then shoot opened up more to get the faster shutter speed. Use of slow shutter speeds, High-ISO, and/or fast films is most likely to cause greater image degradation than is caused by the effects of diffraction.
 
Last edited:
Stewart, you deleted that post before I could respond. The answer is "yes, of course."

Using my eyes, mind and imagination I assume that Rolands smallest aperture was shot at the longest shutter speed. Which shutter speed I cannot authoritatively say. Perhaps someone with a more imaginative eyes, mind and imagination than I can say what that speed was. 🙂
 
Last edited:
tlitody said:
Antenna? They blow about in the wind don't they? Even in a tiny breeze and on a bright sunny day houses create thermals.
Click to expand...

I assume you are referring to my photos. Wind-still, early morning (6am). Results are consistent with expected behavior. And trust me, my naked eye saw more details than the 35/2, even at f11. If you don't believe my tests, read up on Puts and optimum predicted aperture that he measures (and he does say f8 for that lens, averaged across the picture). It is very often larger than f5.6.

My point is not that diffraction doesn't exist. But that it co-exists with other effects, and at f5.6 and below typically matters less than other issues. Diffraction limit might set in at f5.6. Other aberrations get corrected when the aperture closes. The result is mixed, with optimum aperture not being at the diffraction threshold.

Gumby said:
Using my eyes, mind and imagination I assume that Rolands smallest aperture was shot at the lognest shutter speed. Which shutter speed I cannot authoritatively say. Perhaps someone with a more imaginative eyes, mind and imagination than I can say what that speed was. 🙂
Click to expand...

I forgot. Typically I time it such that I can start with 1/1000 wide open, and then go slower with every stop.

Roland.
 
Last edited:
I did some tests on what i considered a windless day. Went from F1.4 through to F22 using the 12.5mm lens. Kept the ISO constant, used a heavy tripod. Results were worthless. I could go to a 100% crop, and see the images stopped down were not as sharp. But realized slight motion or air currents could easily be responsible as the shutter speeds were 1/4second at F22. A lab setup is really required to isolate the effects and claim it is due to diffraction alone. Otherwise, it is speculation and imagination, but not conclusive.
 
Last edited:
tlitody said:
Nope. But I've done the tests years ago and verified for myself that there is a very noticeable difference when you get it right. That is, I could see the difference in the prints.

Antenna? They blow about in the wind don't they? Even in a tiny breeze and on a bright sunny day houses create thermals which are popping off constantly and thermals are very turbulent so don't tell me there was no wind because you can't see thermals which are not depandant on wind. Just so its clear, the attenna is not a good example and I'm not saying those results are wrong but rather making it clear to you that one test proves nothing and just because you haven't observed the effects of diffraction doesn't mean others who have done more stringent test haven't either or that the effect doesn't exist. It's simple physics but that is just theory. In the real world you have to do tests and the tests I did showed diffraction was an observable effect for the lenses I tested.
Click to expand...

Well the thing is, if it were windy the shots with the longest shutter times would be the least sharp ... exactly the opposite to Roland's results, would you agree?

I shall, of course, give you're evidence the weight it deserves when compared to Roland's
 
Gumby said:
Stewart, you deleted that post before I could respond. The answer is "yes, of course."

Using my eyes, mind and imagination I assume that Rolands smallest aperture was shot at the longest shutter speed. Which shutter speed I cannot authoritatively say. Perhaps someone with a more imaginative eyes, mind and imagination than I can say what that speed was. 🙂
Click to expand...

Sorry I was intending to quote the other chap 😱
 
ferider said:
I assume you are referring to my photos. Wind-still, early morning (6am). Results are consistent with expected behavior. If you don't believe me, read up on Puts and optimum predicted aperture that he measures (and he does say f8 for that lens, averaged across the picture). It is very often larger than f5.6.

My point is not that diffraction doesn't exist. But that it co-exists with other effects, and at f5.6 and below typically matters less than other issues. Diffraction limit might set in at f5.6. Other aberrations get corrected when the aperture closes. The result is mixed, with optimum aperture not being at the diffraction threshold.



I forgot. Typically I time it such that I can start with 1/1000 wide open, and then go slower with every stop.

Roland.
Click to expand...

I thought I made it clear. I'm not saying your results are wrong. I'm saying they are not proof in genral that diffraction is not an issue. All they prove for you is at that distance, you need smaller apertures for sharpness assumming attenna was still.

p.s. thermals go up at night time too if air temp is lower than ground temp or roof temp. They are caused by temp differences not absolute temperatures.
 
Brian Sweeney said:
I did some tests on what i considered a windless day. Went from F1.4 through to F22 using the 12.5mm lens. Kept the ISO constant, used a heavy tripod. Results were worthless. I could go to a 100% crop, and see the images stopped down were not as sharp. But realized slight motion or air currents could easily be responsible as the shutter speeds were 1/4second at F22. A lab setup is really required to isolate the effects and claim it is due to diffraction alone. Otherwise, it is speculation and imagination, but not conclusive.
Click to expand...

Vibrating Antenna or not, if you can see something clearly with the naked eye, and you use 1/60 or faster shutter speeds, film will "see" it too. Otherwise TV would not work. And again, the antenna details were very clearly visible with the eye during the test.

My point is exactly that the function of diffraction over aperture can typically not be isolated at all, unless you have a really super sharp lens. I only have a single lens like that, and it's not a Summicron.
 
Last edited:
ferider said:
My point is not that diffraction doesn't exist. But that it co-exists with other effects, and at f5.6 and below typically matters less than other issues. Diffraction limit might set in at f5.6. Other aberrations get corrected when the aperture closes. The result is mixed, with optimum aperture not being at the diffraction threshold.
Click to expand...

That's it.

And about imagination, apart from windy antennas and images becoming fuzzy after f/5.6, there's little imagination on this thread...😀

Cheers,

Juan
 
You must log in or register to reply here.
Back
Top Bottom