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Diffraction on smaller aperture values

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Afagundes
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Message edited at 11/26/2011, 21:39:39 PM by Afagundes
I don't know why the op, parkinsonsniper closed this thread so I am opening it again.



The old thread was Difraction on small apertures



Parkinsonsniper, you said your professor always uses f22, but you didn't say which camera he is using.



That changes everything, if it's a large format he might need to close it down a lot to have sharp images.



On the current DSLR's full frame or APS-C's, you normally stays up to f13, maybe f16 on a full frame.



This has no relationship with exposure as far as I know, it's an optical phenomena.
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Alvera
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Message edited at 01/02/2012, 17:24:42 PM by Alvera
Confirmed, look at Photozone tests, f8 is always the sharpest and around (5.6, 8, 11 - MTF (resolution). On the current DSLR's full frame or APS-C's, like you said. Of course, if we go on movie stage, f64 is very common. :)
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Afagundes
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Message posted at 01/03/2012, 03:31:55 AM by Afagundes
The resolution of an HD movie is much smaller, 1080 lines compared to a 21 Mpixels image, so difraction is not evident even with very tight apertures.



Check this site
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Alvera
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Message posted at 01/03/2012, 06:06:41 AM by Alvera
not digital movies, on film

Very good lecture here: http://en.wikipedia.org/wiki/Group_f/64

The term f/64 refers to a small aperture setting on a large format camera, which secures great depth of field, rendering a photograph evenly sharp from foreground to background. Such a small aperture sometimes implies a long exposure and therefore a selection of relatively slow moving or motionless subject matter, such as landscapes and still life, but in the typically bright California light this is less a factor in the subject matter chosen than the sheer size and clumsiness of the cameras, compared to the smaller cameras increasingly used in action and reportage photography in the 1930s.
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Parkinsonsniper
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Message posted at 07/17/2012, 04:07:27 AM by Parkinsonsniper
Hey...I'm sorry I missed this thread! It's a little (!) late maybe, but I still want to answer :))

He was using a Nikon D300 and D700. He always use f22 and his photos are tack sharp. When I use f22, my photos are almost blurry! I have the same paraflash set and high quality lenses. I can't solve this...he don't tell me the tip, because he wants me to find the answer!

...and here I am cheating :))

Afagundes thanks for your effort to help, I'm sorry to miss this thread.

Best regards...
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Parkinsonsniper
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Message posted at 07/17/2012, 04:11:14 AM by Parkinsonsniper
I just took a look at that thread now, I don't know why I closed it! I think I clicked on the "close thread" button mistakenly :)) there is no reason to close it...
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Bradcalkins
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Message edited at 07/17/2012, 10:31:39 AM by Bradcalkins
I am at a loss to explain why exposure (aside from aperture selected) would have any impact on sharpness. I can say, however, that certain lenses in the telephoto range seem almost immune to the effects of diffraction. The new Olympus 75mm is very sharp right down to f/16 (which on micro four thirds is past diffraction). Similarly the Canon 135mm f/2 is still under 2 blur units on SLRGear's review at f/22, as is the Zeiss 100mm Makro Planar. Stopping down adds sharpness, but stopping down adds diffraction. I suspect some lenses add sharpness further down the aperture ring more than others, offsetting the effects of diffraction. It isn't that diffraction isn't present, simply that they keep getting sharper at small apertures where other lenses don't.
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Alvera
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Message posted at 07/17/2012, 15:35:34 PM by Alvera
english please
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Bradcalkins
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Message posted at 07/17/2012, 20:37:00 PM by Bradcalkins
I guess my point is that while most lenses are sharpest in the middle apertures (f/8) there are many telephoto lenses that are sharper at f/16 or even f/22 than most lenses at f/8.

Doesn't explain anything about the origianl question, though :)
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Parkinsonsniper
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Message posted at 07/18/2012, 03:13:42 AM by Parkinsonsniper
Alvera...ehhmm...my noble king, you can always make me smile with your brave answers! :)))

Almost all of the pro photographers use f22, so I'm sure there is a solution for this diffraction thing!

Good news is, I think I solved the problem...but let me test my answer before I publish it! :))
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Afagundes
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Message posted at 07/18/2012, 05:48:30 AM by Afagundes

Originally posted by Bradcalkins:
Quoted Message: I guess my point is that while most lenses are sharpest in the middle apertures (f/8) there are many telephoto lenses that are sharper at f/16 or even f/22 than most lenses at f/8.Doesn`t explain anything about the origianl question, though :)


Brad, I am a little skeptical about that, in my tests all images look tack sharp at f8, at f16 difraction starts to show up, f22 kind of bad, f32 very bad.

If I downsample, than all difraction is gone and the image looks tack sharp.

This happens with all my lenses, from 17 to 300 mm and for what I understand is an optical problem, and I see no way to avoid it.

What you can do is use post processing sharpness techniques,

This is for a full frame camera, for an APS-C, f16 difraction is much more visible.

Pros might be using a large format camera, in this case they have to close it down much more to have DOF, and the difraction will only show up with smaller apertures.

In a 4x3", for example, difraction would show up with f64 (theoretically), therefore, the f64 group of Ansel Adams who used this kind of camera.

f16 in a full frame will give more or less the same DOF as f64 in a 4x3", f11 probably would have the same DOF in an APS-C, so there is no reason to close it down more than that, IMHO.
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Parkinsonsniper
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Message posted at 07/18/2012, 05:53:43 AM by Parkinsonsniper
Afagundes welcome and thanks for opening the thread again. I agree with you, it's a rule of physics and there is no way of avoiding it. My solution is kind of a sharpening with playing with radius. I suppose that higher radius values will bring back the sharpness of diffraction. I will test it as soon as possible and share the results here. I think it is going to work.
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Alvera
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Message posted at 07/18/2012, 10:27:13 AM by Alvera

Originally posted by Bradcalkins:
Quoted Message: there are many telephoto lenses that are sharper at f/16 or even f/22 than most lenses at f/8.

yes, my 55-300 is sharpest at f/11
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Alvera
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Message posted at 07/18/2012, 12:21:28 PM by Alvera

Originally posted by Parkinsonsniper:
Quoted Message: Alvera...ehhmm...my noble king, you can always make me smile with your brave answers! :)))Almost all of the pro photographers use f22, so I`m sure there is a solution for this diffraction thing!Good news is, I think I solved the problem...but let me test my answer before I publish it! :))


I am here only to please you, Sir. What is a "f"? F was my letter grade at school...
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Bradcalkins
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Message posted at 07/18/2012, 12:55:59 PM by Bradcalkins

Originally posted by Parkinsonsniper:
Quoted Message: Alvera...ehhmm...my noble king, you can always make me smile with your brave answers! :)))Almost all of the pro photographers use f22, so I`m sure there is a solution for this diffraction thing!Good news is, I think I solved the problem...but let me test my answer before I publish it! :))


Make sure you come back and let us know - we don't need another Fermat's Last Theorem to ponder for 400 years :)
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Alvera
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Message posted at 07/18/2012, 14:11:29 PM by Alvera
He is a scientist from Area 51. So please let him to solve the problem. You will see, in the next post will ask for more funds :)
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Parkinsonsniper
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Message posted at 07/18/2012, 14:45:42 PM by Parkinsonsniper
I need a Nikon D400, Nikon D800, a Hasselblad BlaBla and couple of lenses for more reliable tests!

I think the "pros use mid format" idea is a good point. I promise to share the results with before after shots as soon as possible. Next week I'm on vacation and I will have lots of time for such things :)

I think the right radius will decrease the effect of diffraction...we will see :)
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Androniques
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Message edited at 07/18/2012, 19:44:19 PM by Androniques
Parkinsonsniper, don't you get it? It is a matter of faith, nothing more... You've got to believe in no diffraction at f22 for cropped sensors, and lenses for that reason! ;))

update: Seriously, I always thought (as I was taught from different sources) that diffraction is always present and a normal/ideal lens (if forgetting about various aberrations dealt with by extra aspherical elements) would give the sharpest image on the focal plane at the widest aperture (ok, with the strongest boke/blur for parts out of focus). Reducing the hole, i.e. increasing the aperture f-number, will reduce the sharpness while increasing the DOF. At some point, i.e. aperture f-number, a particular lens will suffer from too much of blurring in the focal plane, which will affect the image produced on the sensor/film when the visible blurring becomes comparable in size with the unit photo-element, i.e. pixel. That's the theory, the practice is what you manage to get with your combination of lens+sensor. Don't forget to switch off the IS/VR mechanisms and shoot on a tripod, which can affect the result.
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Afagundes
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Message posted at 07/18/2012, 20:07:03 PM by Afagundes

Originally posted by Parkinsonsniper:
Quoted Message: :)I think the right radius will decrease the effect of diffraction...we will see :)


I think you are better of with f11 and using sharpness techniques to add the impression of DOF than trying to add sharpness to an image where the difraction is already showing and blurring pixels, but I will wait for the results of your experience.
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Alvera
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Message edited at 07/19/2012, 01:59:48 AM by Alvera

Originally posted by Androniques:
Quoted Message: Parkinsonsniper, don`t you get it? It is a matter of faith, nothing more... You`ve got to believe in no diffraction at f22 for cropped sensors


lol

Please let me share my result. Look at my last approved photo, I shoot only at f8 or f9.5 in studio. At f8 the green umbrella is open. I will post another photo with f22, you all will see at that aperture the umbrella is closed!

   Little girl green umbrella isolated white   
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