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11-19-2013, 03:49 PM   #1
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Diffraction limits

I read in another thread about a diffraction calculator.

Maybe it was this one:
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

So there is a diffenrence between the K-3 with 24 megapixel and the K-5 with just 16mp. Diffraction is showing in earlier.

Now the question:
- When does it enter that it shows
- Is that more limited in practicle use then with the K-5
- What apertures are great - good - usable - not usable?

Thanks for answers.

11-19-2013, 04:06 PM   #2
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Nice find ! Thanks !
Would love to hear the answers too btw --manntax
11-19-2013, 04:21 PM   #3
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If I’m not mistaken diffraction also depends on lens to, so different lens will have different aperture when diffraction will show. Only tests will show.
11-19-2013, 04:24 PM   #4
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QuoteOriginally posted by i83N Quote
If I’m not mistaken diffraction also depends on lens to, so different lens will have different aperture when diffraction will show. Only tests will show.
And in general is there anything to say about it.

Say I use some of my lenses (FA31mm, DA*55mm, FA*85mm) on f10 and what would be the step back? Going to f8 or is that to simple to say.

11-19-2013, 04:40 PM - 1 Like   #5
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I would say that as a general rule, don't venture above F11 or F13 and you should be fine.

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11-19-2013, 04:51 PM   #6
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QuoteOriginally posted by RonHendriks1966 Quote
And in general is there anything to say about it.

Say I use some of my lenses (FA31mm, DA*55mm, FA*85mm) on f10 and what would be the step back? Going to f8 or is that to simple to say.
QuoteOriginally posted by LENS DIFFRACTION & PHOTOGRAPHY:
Camera systems typically have an optimal aperture in between the largest and smallest settings; with most lenses, optimal sharpness is often close to the diffraction limit, but with some lenses this may even occur prior to the diffraction limit.
If those lens optima shapes is on f8, than yes.

Than again, AA filer actually is a diffraction grating, so K-5 can show signs of diffraction earlier than K-3, witch don’t have AA filter.
11-19-2013, 05:01 PM   #7
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What if the k-3 files are shot at F13 and scaled to 16mp vs the k-5IIs shot at F13?
How much blur does diffraction introduce? If it is a specific and equal dimension between the two sensors, then shouldn't a scaled down image be equal? As in - the smaller pixels see diffraction while the larger one doesn't - however the diffraction blur does not exceed the equivalent size of pixels when scaled down.
11-19-2013, 05:02 PM - 1 Like   #8
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I think I shared that link (that site has great tutorials, all of them!)
Diffraction doesn´t depend on the lens. Interaction of light with the sensor, the lens just provides more or less light but the f-stop is meant to keep that ammount of light equivalent for every focal length so it is not important. Now, if you take "étendue" into account, then FL does play but that´s a different topic.. Great read on that: Clarkvision.com: Low Light Photography: When f/ratio Does not Tell the Whole Story
If you click "show advanced" on the cambridge Diffraction Limit Calculator, you´ll see the parameters involved in diffraction but, how much of each do you nide to make diffraction visible? Complete the chart and write down some numbers.

Ron, what are your typical printing sizes and viewing distance? These two will determine what´s is in acceptable focus and what´s not (this is called CoC = Circle of Confusion). The CoC is what also define your DoF = Depth of field, of course... which you control with the lens aperture. And aperture also defines the "airy disk" which is the minimum area of detail an aperture value allows to be resolved (relative to a given pixel size). So there´s a trade off between what´s in focus (CoC) and how big the Airy Disk gets (bigger, less detail) and both are controled with the aperture value!
As long as the CoC (what´s considered in focus) is bigger than the airy disk, you´ll be safe from diffraction.
So, you want to shoot a hockey player with your new K-3, before clicking you think "I´d like to do a 20x30cm ( print and see it at reding distance = 25cm). You may close down to f/16 without any problem.
"Ok great" let´s make a 40x60cm print and view it at 25cm too, what happens then?" Well, then try not go further than f/11 to keep good detail.

That helps?

11-20-2013, 03:16 AM   #9
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QuoteOriginally posted by carrrlangas Quote
I think I shared that link (that site has great tutorials, all of them!)
Diffraction doesn´t depend on the lens. Interaction of light with the sensor, the lens just provides more or less light but the f-stop is meant to keep that ammount of light equivalent for every focal length so it is not important. Now, if you take "étendue" into account, then FL does play but that´s a different topic.. Great read on that: Clarkvision.com: Low Light Photography: When f/ratio Does not Tell the Whole Story
If you click "show advanced" on the cambridge Diffraction Limit Calculator, you´ll see the parameters involved in diffraction but, how much of each do you nide to make diffraction visible? Complete the chart and write down some numbers.

Ron, what are your typical printing sizes and viewing distance? These two will determine what´s is in acceptable focus and what´s not (this is called CoC = Circle of Confusion). The CoC is what also define your DoF = Depth of field, of course... which you control with the lens aperture. And aperture also defines the "airy disk" which is the minimum area of detail an aperture value allows to be resolved (relative to a given pixel size). So there´s a trade off between what´s in focus (CoC) and how big the Airy Disk gets (bigger, less detail) and both are controled with the aperture value!
As long as the CoC (what´s considered in focus) is bigger than the airy disk, you´ll be safe from diffraction.
So, you want to shoot a hockey player with your new K-3, before clicking you think "I´d like to do a 20x30cm ( print and see it at reding distance = 25cm). You may close down to f/16 without any problem.
"Ok great" let´s make a 40x60cm print and view it at 25cm too, what happens then?" Well, then try not go further than f/11 to keep good detail.

That helps?
Yes that helps!

Toyd around a little and there isn't that much difference between the two sensors.

- only difference is with the 20/20 vision (but I don't know what that means)

Well I make A3 prints, so that is no problem. I also done some A1 prints lately, and those are also good. I've done two prints 150cm hight and going to make some more off the next shoot (to fill a gym) and that also looks good as I see it. Distance to look at it will be 3 to 5 meters.
11-20-2013, 04:06 AM   #10
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QuoteOriginally posted by RonHendriks1966 Quote
So there is a diffenrence between the K-3 with 24 megapixel and the K-5 with just 16mp. Diffraction is showing in earlier.
As in: you will be able to detect it earlier. Resolution-wise, you'll get more or at least the same level of detail with the higher resolution sensor (everything else but diffraction and resolution ignored).
The image projected on the sensor's surface (where diffraction occurs) is completely unaware of the sensor's resolution
11-20-2013, 06:36 AM   #11
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There seems to be some misconceptions lurking around in this thread.

Diffraction is a property of the lens, not the sensor.

When your sensor out-resolves your lens (be it because of diffraction or other optical flaws/limits) you will perceive a decrease in image quality.

The article you link to is fine but makes some simplifications. for instance, since what we photographers call "aperture" is in fact a ratio of the size of the aperture stop (the smallest part along the light path, if you will) and the focal length, you cannot just say "camera x shows diffraction effects at f11". It will vary with focal length, and with the actual position of the aperture stop.

The perceived resolution will not only depend on diffraction effects (or lack thereof). The types of glass used, their quality, the number of surfaces, the coatings, the curvature of the various lens elements, and many other parameters will impact what we call sharpness.
11-20-2013, 08:05 AM   #12
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QuoteOriginally posted by bdery Quote
There seems to be some misconceptions lurking around in this thread.

Diffraction is a property of the lens, not the sensor.

When your sensor out-resolves your lens (be it because of diffraction or other optical flaws/limits) you will perceive a decrease in image quality.

The article you link to is fine but makes some simplifications. for instance, since what we photographers call "aperture" is in fact a ratio of the size of the aperture stop (the smallest part along the light path, if you will) and the focal length, you cannot just say "camera x shows diffraction effects at f11". It will vary with focal length, and with the actual position of the aperture stop.

The perceived resolution will not only depend on diffraction effects (or lack thereof). The types of glass used, their quality, the number of surfaces, the coatings, the curvature of the various lens elements, and many other parameters will impact what we call sharpness.
Thanks for putting in your knowledge.

Except that things didn't get any easier.

So my lenses to use are all top quality with the FA31mm, DA*55mm and FA*85mm. Where I already somewhere stated that that the DA*55 beats the FA*85 and I already knew that the FA31mm was the poor child in this groupe.

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/239415-da-55mm-fa-85mm.html

That all with not knowing why.

Anything to say about those focal lengths without having the lenses in your hands to test?
11-20-2013, 08:48 AM   #13
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QuoteOriginally posted by bdery Quote
Diffraction is a property of the lens, not the sensor.
How could it be a property of the lens, when what is being compared here is diffraction effects for 24 vs 16 Megapixels? Diffraction effects start showing at wider apertures for both smaller sensors and smaller pixels, the question is how much for an specific application.
11-20-2013, 09:02 AM   #14
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That linked diffraction calculator says in 1.5x sensor diffraction start to be problem from f16. Yes I agree this but i would not take this as general rule cos it depends on lens liitle if its problem or not. But f22 I would make general rule already and f22 should be avoided...but I have few lenses still that can use f22 and result looks ok to me. Most lenses i have f22 will make bad IQ. Like my da 55-300 in 300mm IQ seems to be best f16...

That calculator says also in FF difftractionstart to be problem from f32
11-20-2013, 11:28 AM   #15
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QuoteOriginally posted by carrrlangas Quote
How could it be a property of the lens, when what is being compared here is diffraction effects for 24 vs 16 Megapixels?
Because if your lens out-resolves your sensor, your sensor is the limiting component of your imaging system. In that case you might not see the diffraction effect (or any other aberration for that matter). If your sensor out-resolves your lens, then every optical flaw will be apparent in your final image.

In other words, the sensor's ability to create an image when diffraction is apparent does not relate to the actual presence of diffraction.
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