Olympus UK E-System User Group
Olympus UK E-System User Group

Join our unique resource for Olympus Four Thirds E-System DSLR and Pen and OM-D Micro Four Thirds photographers. Show your images via our free e-group photo gallery. Please read the e-group.uk.net forum terms and conditions before posting for the first time. Above all, welcome!


Go Back   Olympus UK E-System User Group > Site news and information > Tutorials, Informative & Classic threads

Tutorials, Informative & Classic threads A new e-Group area for all the wonderful tutorials and helpful threads put on here by our members. Tutorials on using software, camera hardware - and feel free to request a tutorial if you need assistance!

Reply
 
Thread Tools Display Modes
  #1  
Old 12th July 2017
Phill D's Avatar
Phill D Phill D is offline
Full member
 
Join Date: Apr 2011
Location: Derbyshire
Posts: 9,814
Thanks: 1,182
Thanked 1,407 Times in 1,299 Posts
Likes: 1,030
Liked 2,340 Times in 1,112 Posts
Diffraction confusion!

Well I thought I understood the diffraction phenomenon but this link Dave recently posted has me a bit confused.

http://www.cambridgeincolour.com/tut...ensor-size.htm

There is a diffraction limited aperture estimator and if you follow the diffraction limits and photography link there is a diffraction limit calculator.
So my dilemma,
I tried the diffraction limit calculator and for a 4/3 slr then it says that f11 is not diffraction limited but f16 is. Now that is pretty much what I was working to from a workshop I did where the diffraction point was estimated on my EM1 at around f12/13, hence I've usually tried to use around f11 for my highest resolution and dof landscape shots when I have sufficient light.
OK so far
However, when I looked at the advanced version of the calculator or the simpler Diffraction limited aperture estimator on the original link they both give the opportunity to input the sensor resolution in Megapixels. Now I thought that, to quote Cambridge in colour themselves
"Diffraction thus sets a fundamental resolution limit that is independent of the number of megapixels, or the size of the film format. It depends only on the f-number of your lens, and on the wavelength of light being imaged."

So why input the megapixels? and if you do the calculators give a very different answer for the diffraction aperture limit.
Using the simpler Diffraction Limited Aperture Estimator for a 20 Megapixel input I get f6.5 as the diffraction limit and for a 16 Megapixel input I get f7.3....?
hence I'm now a tad confused.
So
- does my new EM1 Mk2 have a bigger aperture diffraction limit to my old Mk1? especially if diffraction is supposed to be independent of the number of megapixels?
- should I be working at f6.3 for my landscapes rather than f11 for max resolution? (assuming dof isn't an issue)

Any help clearing this up would be much appreciated.
Thanks.
Reply With Quote
  #2  
Old 12th July 2017
Petrochemist Petrochemist is offline
Full member
 
Join Date: Apr 2015
Location: N Essex
Posts: 727
Thanks: 36
Thanked 81 Times in 74 Posts
Likes: 212
Liked 126 Times in 92 Posts
Re: Diffraction confusion!

The physical degree of diffraction isn't affected by resolution/sensor size, but how soon that diffraction might be noticeable is. If diffraction is only blurring your image by the width of a pixel it won't be noticeable however you output your image.
If it's covering 5 pixels but your reducing your image 6 fold to publish on the web the diffraction won't be an issue, but if you're cropping your image and want a sharp print it may well be that anything larger than the pixel size on your new super megapixel camera will be an issue...

When pixel peeping the effects of diffraction will be seen sooner on your new Mk2. It probably won't be an issue if just printing to A4 or using on-line. It may not be an issue printed at A3.
DOF is another factor that depends on the final output. What looks perfectly focused on a 6x4 print might look quite soft on an A3 version especially if viewed from the same distance.

I believe the 'circle of confusion' is used in the actual formula for both DOF & diffraction to define how much things can be softened before it becomes noticeable. The name has always struck me as very appropriate as it seems to cause no end of confusion! It can be used at the pixel size to determine when it will be noticeable on pixel peeping, of at a number suitable for the output print & allowing for the degree of enlargement in producing that print. Many sources just set a standard output such as 10x8 viewed at arms reach, & so remove the variable from their equations.
__________________
Mike
Compulsive photographic Dabbler.
Flickr
Reply With Quote
  #3  
Old 12th July 2017
pdk42's Avatar
pdk42 pdk42 is offline
Full member
 
Join Date: Apr 2013
Location: Leamington Spa
Posts: 5,710
Thanks: 370
Thanked 1,257 Times in 942 Posts
Likes: 150
Liked 5,995 Times in 1,953 Posts
Re: Diffraction confusion!

Quote:
Originally Posted by Petrochemist View Post
The physical degree of diffraction isn't affected by resolution/sensor size, but how soon that diffraction might be noticeable is. If diffraction is only blurring your image by the width of a pixel it won't be noticeable however you output your image.
If it's covering 5 pixels but your reducing your image 6 fold to publish on the web the diffraction won't be an issue, but if you're cropping your image and want a sharp print it may well be that anything larger than the pixel size on your new super megapixel camera will be an issue...

When pixel peeping the effects of diffraction will be seen sooner on your new Mk2. It probably won't be an issue if just printing to A4 or using on-line. It may not be an issue printed at A3.
DOF is another factor that depends on the final output. What looks perfectly focused on a 6x4 print might look quite soft on an A3 version especially if viewed from the same distance.

I believe the 'circle of confusion' is used in the actual formula for both DOF & diffraction to define how much things can be softened before it becomes noticeable. The name has always struck me as very appropriate as it seems to cause no end of confusion! It can be used at the pixel size to determine when it will be noticeable on pixel peeping, of at a number suitable for the output print & allowing for the degree of enlargement in producing that print. Many sources just set a standard output such as 10x8 viewed at arms reach, & so remove the variable from their equations.
I think you nailed it Mike! If you get past all the physics of it and look to the practicalities as it applies to photography then the essential points are:

- Diffraction increases as a function of F stop. The focal length of the lens is irrelevant.

- The apparent loss of sharpness will increase as the magnification of the original image to final image increases. This means that smaller sensors will be more impacted by diffraction effects.

- As pixel pitch decreases (e.g. by packing more pixels into the same area) then the impact of diffraction will become more evident simply because the higher resolution of the sensor has the potential to show more detail.


Personally, I consider f8 to be my limit in u43. I might push it to f11 if I need the extra DOF or maybe to pull the shutter speed down.
__________________
Paul
E-M1ii, Pen-F and too many lenses
flickr
Portfolio Site
Instagram
Reply With Quote
The Following Users Liked This Post:
Petrochemist (12th July 2017), RobEW (3rd October 2017), wornish (12th July 2017)
  #4  
Old 12th July 2017
raichea raichea is offline
Full member
 
Join Date: Oct 2011
Location: Hampshire
Posts: 683
Thanks: 88
Thanked 114 Times in 94 Posts
Likes: 106
Liked 116 Times in 79 Posts
Re: Diffraction confusion!

Quote:
Originally Posted by pdk42 View Post
- The apparent loss of sharpness will increase as the magnification of the original image to final image increases. This means that smaller sensors will be more impacted by diffraction effects.

- As pixel pitch decreases (e.g. by packing more pixels into the same area) then the impact of diffraction will become more evident simply because the higher resolution of the sensor has the potential to show more detail.
I don't think the pixel pitch matters unless you're viewing at 100%... the viewed image size and viewer distance is what determines the perceived sharpness. As someone said earlier the DoF estimates generally assume a standard print size/viewing distance and diffraction is essentially the same process.
__________________
Steve
Reply With Quote
  #5  
Old 3rd October 2017
RobEW RobEW is offline
Full member
 
Join Date: Feb 2017
Location: Nottingham
Posts: 2,036
Thanks: 165
Thanked 74 Times in 68 Posts
Likes: 1,191
Liked 187 Times in 128 Posts
Re: Diffraction confusion!

Quote:
Originally Posted by pdk42 View Post
....
Personally, I consider f8 to be my limit in u43. I might push it to f11 if I need the extra DOF or maybe to pull the shutter speed down.
I've been trying as narrrow as f/14 in macro work with moving subjects, as I lose far more shots due to DoF limitations than to diffraction.

Quick question. what does diffraction actually look like? How can I look at an image and say that it's suffering diffraction? Is it just an overall lack of sharpness? (If so it's hard to be sure whether diffraction or soething else caused it)
Reply With Quote
  #6  
Old 12th July 2017
David M's Avatar
David M David M is offline
Full member
 
Join Date: Dec 2007
Location: A Brit now living in Ontario, Canada.
Posts: 6,605
Thanks: 39
Thanked 678 Times in 640 Posts
Likes: 254
Liked 1,313 Times in 792 Posts
Re: Diffraction confusion!

Diffraction is a very recent invention. It's only purpose is to give internet "experts" and trolls something to annoy forum users with.















Actually I seem to remember covering it when studying photography. But in those days it was in reference to using large format and really, really tiny apertures IIRC. And surely, if that Cambridge in Colour quote is correct the number of megapixels will matter as the smaller the pixel pitch the more effect the varying wavelengths of light will have.
__________________
It's the image that's important, not the tools used to make it.

David M's Photoblog or follow me on Instagram.
Reply With Quote
The Following Users Liked This Post:
benvendetta (13th July 2017), Jim Ford (12th July 2017), MJ224 (12th July 2017)
  #7  
Old 12th July 2017
Michael Sewell's Avatar
Michael Sewell Michael Sewell is offline
Full member
 
Join Date: Mar 2017
Location: Burnley
Posts: 382
Thanks: 24
Thanked 52 Times in 35 Posts
Likes: 89
Liked 220 Times in 100 Posts
Re: Diffraction confusion!

I have to say, way back in the day of film, I used the aperture most conducive to the image I wanted to create.

A philosophy I still pursue today.
Reply With Quote
The Following Users Liked This Post:
MJ224 (12th July 2017), RobEW (3rd October 2017)
  #8  
Old 12th July 2017
Petrochemist Petrochemist is offline
Full member
 
Join Date: Apr 2015
Location: N Essex
Posts: 727
Thanks: 36
Thanked 81 Times in 74 Posts
Likes: 212
Liked 126 Times in 92 Posts
Re: Diffraction confusion!

Quote:
Originally Posted by Michael Sewell View Post
I have to say, way back in the day of film, I used the aperture most conducive to the image I wanted to create.

A philosophy I still pursue today.
And always the right one, unless that creates too much diffraction softening & focus stacking can be used for the subject to give the DOF required without the softening.

Outside of the field of macro I don't think those exceptions are likely to occur.
__________________
Mike
Compulsive photographic Dabbler.
Flickr
Reply With Quote
  #9  
Old 13th July 2017
benvendetta's Avatar
benvendetta benvendetta is offline
Full member
 
Join Date: Sep 2008
Location: Pontypool, South Wales
Posts: 3,746
Thanks: 83
Thanked 297 Times in 262 Posts
Likes: 167
Liked 339 Times in 229 Posts
Re: Diffraction confusion!

Quote:
Originally Posted by Michael Sewell View Post
I have to say, way back in the day of film, I used the aperture most conducive to the image I wanted to create.

A philosophy I still pursue today.
Absolutely Michael!
__________________
Dave

E-M1 Mk2, Pen F, HLD-9, 17, 25, 45, 60 macro, 12-40 Pro, 40-150 Pro, 12-50, 40-150, 75-300, MC-14, MMF-3 (all micro 4/3rds), 7-14 (4/3rds), 50, 135 (OM), GoPro Hero 3, Novo/Giottos/ Manfrotto supports. Lowepro, Tamrac, Manfrotto, and Billingham bags.

External Competition Secretary, Cwmbran PS & Welsh Photographic Federation Judge
Reply With Quote
The Following User Liked This Post:
MJ224 (13th July 2017)
  #10  
Old 12th July 2017
Michael Sewell's Avatar
Michael Sewell Michael Sewell is offline
Full member
 
Join Date: Mar 2017
Location: Burnley
Posts: 382
Thanks: 24
Thanked 52 Times in 35 Posts
Likes: 89
Liked 220 Times in 100 Posts
Re: Diffraction confusion!



E-M1 mkII 1/250th sec ISO64 12-40mm f16
Reply With Quote
The Following Users Liked This Post:
Johnheatingman (12th July 2017), MJ224 (12th July 2017), Phill D (12th July 2017), RobEW (3rd October 2017), Ross the fiddler (13th July 2017), Zuiko (12th July 2017)
  #11  
Old 12th July 2017
MJ224's Avatar
MJ224 MJ224 is online now
Full member
 
Join Date: May 2016
Location: Carmarthenshire
Posts: 13,009
Thanks: 878
Thanked 690 Times in 641 Posts
Likes: 6,507
Liked 3,526 Times in 1,639 Posts
Re: Diffraction confusion!

She must be about to fall over,..................

Well defracted I think.....

(joke)
__________________
My Sailing Page

My Flickr
Reply With Quote
The Following User Liked This Post:
Michael Sewell (12th July 2017)
  #12  
Old 12th July 2017
Zuiko's Avatar
Zuiko Zuiko is offline
Administrator
 
Join Date: Nov 2007
Location: Dunmow, Essex
Posts: 22,066
Thanks: 1,984
Thanked 3,151 Times in 2,459 Posts
Likes: 3,385
Liked 4,455 Times in 2,116 Posts
Re: Diffraction confusion!

Quote:
Originally Posted by Michael Sewell View Post


E-M1 mkII 1/250th sec ISO64 12-40mm f16
I can just imagine the bride saying, "That's a wonderful picture but it's a shame it's diffraction limited, I reckon he must have shot at f16."
__________________
John

"A hundredth of a second here, a hundredth of a second there ó even if you put them end to end, they still only add up to one, two, perhaps three seconds, snatched from eternity." ~ Robert Doisneau
Reply With Quote
The Following User Liked This Post:
Michael Sewell (12th July 2017)
  #13  
Old 6th October 2017
Bassman51's Avatar
Bassman51 Bassman51 is offline
Full member
 
Join Date: Dec 2016
Location: NJ, USA
Posts: 50
Thanks: 2
Thanked 6 Times in 6 Posts
Likes: 5
Liked 18 Times in 14 Posts
Re: Diffraction confusion!

Quote:
Originally Posted by Michael Sewell View Post


E-M1 mkII 1/250th sec ISO64 12-40mm f16
Michael, a stunning image. Which breaks all the rules, thereby showing how silly rules can be:

- too much defraction
- glare
- purple blobs
- Backlit by the sun, which bleeds all over

Wish I could produce such technically deficient images all the time. Or even some of the time.
__________________
Instagram: TheBassmanBlog
My Blog: TheBassmanBlog.com
My Pictures: abbeyworks.smugmug.com
Reply With Quote
The Following User Says Thank You to Bassman51 For This Useful Post:
Michael Sewell (23rd April 2018)
The Following User Liked This Post:
Michael Sewell (23rd April 2018)
  #14  
Old 6th October 2017
Ricoh Ricoh is offline
Full member
 
Join Date: Apr 2014
Location: Lancashire
Posts: 5,792
Thanks: 592
Thanked 421 Times in 373 Posts
Likes: 787
Liked 1,919 Times in 1,143 Posts
Re: Diffraction confusion!

Quote:
Originally Posted by Bassman51 View Post
Michael, a stunning image. Which breaks all the rules, thereby showing how silly rules can be:

- too much defraction
- glare
- purple blobs
- Backlit by the sun, which bleeds all over

Wish I could produce such technically deficient images all the time. Or even some of the time.
I think she's falling for him
__________________
Steve

on flickr
Reply With Quote
The Following User Liked This Post:
Michael Sewell (23rd April 2018)
  #15  
Old 12th July 2017
wornish's Avatar
wornish wornish is offline
Senior Member
 
Join Date: Sep 2015
Location: Cheshire
Posts: 5,784
Thanks: 327
Thanked 530 Times in 410 Posts
Likes: 2,686
Liked 1,531 Times in 754 Posts
Re: Diffraction confusion!

In the film days people didn't pixel peep as they do today.

Diffraction is a digital phenomenon but it does exist. You can take action to minimise it or choose to ignore it. In most cases its not noticeable but not all.
__________________
Dave

My Flickr
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Lens Confusion of GAS MJ224 Standard zoom and mid range 13 4th November 2017 07:45 AM
Seasonal confusion Mrs T Foto Fair 6 3rd November 2016 08:30 PM
No Gender Confusion with this one Nick Temple-Fry Foto Fair 4 18th December 2009 12:47 AM
Confusion on the track andym Foto Fair 1 10th February 2009 02:11 PM
Confusion over My Mode StephenL Olympus E-3 4 29th November 2008 03:57 PM


All times are GMT. The time now is 07:40 AM.


© The Write Technology Ltd, 2007-2019, All rights reservedAd Management plugin by RedTyger