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Olympus OM-D E-M5 The first Micro Four Thirds camera from Olympus with an integrated Electronic Viewfinder

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Old 17th June 2017
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Diffraction Testing.

I was a bit supprised to see a comment that F8 was well into the diffraction zone. The D7100 has the same pixel pitch as the M5 and I take everything at F8 .F11 so I carried out some test on the 40-150 at 150.
Up to F11 there was no detectable degredation but at F16 and particularly F22 the degredation was quite marked.
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Old 17th June 2017
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Re: Diffraction Testing.

Worth checking the link in this post as it contains a useful link to a calculator for expected diffraction.
Your results are I think in line with their results, bearing in mind they do point out the results can vary in practice due to factors such as lens quality etc.
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Old 17th June 2017
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Re: Diffraction Testing.

I'm afraid to suggest it, but I think the old catch cry of the FF fanboys "equivalence" comes into this. The pixel density may be the same but I think the sensor size matters here as well with regard to equivalent DoF & "equivalent" aperture, therefore the smaller aperture with the smaller sensor results in greater DoF & diffraction earlier too. That's my guess anyhow.

With that suggestion, use the appropriate aperture for the system being used & the occasion with desired result.
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Old 17th June 2017
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Re: Diffraction Testing.

Quote:
Originally Posted by Ross the fiddler View Post
I'm afraid to suggest it, but I think the old catch cry of the FF fanboys "equivalence" comes into this. The pixel density may be the same but I think the sensor size matters here as well with regard to equivalent DoF & "equivalent" aperture, therefore the smaller aperture with the smaller sensor results in greater DoF & diffraction earlier too. That's my guess anyhow.

With that suggestion, use the appropriate aperture for the system being used & the occasion with desired result.
I'd have to agree Ross.
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Old 17th June 2017
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Re: Diffraction Testing.

Re-post of something I did some time ago:

I finally got round to testing the idea of illuminating the subject with a blue light to reduce the effect of diffraction.

I pressed to service my ever co-operative muse for this crude set of tests



With the camera set to f/22 and manual focus, I took 3 pictures.
The one above, with the bare flash, one with a Red gel over the flash and another with a Blue gel





I then removed the colour from the RAW files, examined them and cropped an area which I think best shows the effect.

RED Light


Blue Light


The filters used are very saturated "effects" filters and beyond any colours that you would get from natural light, but serve to show how the longer wavelength of the red light is diffracted more than the short wavelength blue light.

As we all know when using filters on the lens for B&W photography, they alter the contrast and other aspects of the final image, depending on how the subject absorbs and reflects the different coloured light.

What is interesting is just how good an Olympus 14-42 kit lens is at f/22
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Old 17th June 2017
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Re: Diffraction Testing.

Good to see theory is holding true
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Old 18th June 2017
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Re: Diffraction Testing.

Just trying to see what F stops not to use ....just that simple and hoping some others my be interested to know the result. Why all the knicker twisting I dont know
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Old 18th June 2017
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Re: Diffraction Testing.

Quote:
Originally Posted by Pistnbroke View Post
Just trying to see what F stops not to use ....just that simple and hoping some others my be interested to know the result. Why all the knicker twisting I dont know
Why start a thread if you don't want a discussion?
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Re: Diffraction Testing.

My original tests with red and blue light were aimed at determining and as a demonstration at clubs, etc., the effect and the information to allow others to consider using a wider aperture when photographing a sunset landscape and smaller aperture for mountain snow scenes.

But the softening effect is often desired for the warm calming sunset, whereas the sharpest clearest details of high altitude mountain snowscapes make a big difference to the perceived IQ.

It's all a bit "nerdy" when talked about in numbers, tables and charts, and as always a picture of what is being discussed speaks volumes.

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Old 18th June 2017
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Re: Diffraction Testing.

Quote:
Originally Posted by Graham_of_Rainham View Post
My original tests with red and blue light were aimed at determining and as a demonstration at clubs, etc., the effect and the information to allow others to consider using a wider aperture when photographing a sunset landscape and smaller aperture for mountain snow scenes.

But the softening effect is often desired for the warm calming sunset, whereas the sharpest clearest details of high altitude mountain snowscapes make a big difference to the perceived IQ.

It's all a bit "nerdy" when talked about in numbers, tables and charts, and as always a picture of what is being discussed speaks volumes.

Great for anyone who received a grade U in physics!
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Old 18th June 2017
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Re: Diffraction Testing.

Quote:
Originally Posted by Michael Sewell View Post
Worth checking the link in this post as it contains a useful link to a calculator for expected diffraction.
Your results are I think in line with their results, bearing in mind they do point out the results can vary in practice due to factors such as lens quality etc.
The calculator on that "Cambridge in Colour" link suggests f/11 is okay on Oly M43 cameras (16MP, 50% crop factor), but by f/16 you are beginning to get diffraction limitations. This is irrespective of what lens you are using. Very interesting.
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Re: Diffraction Testing.

Quote:
Originally Posted by RobEW View Post
The calculator on that "Cambridge in Colour" link suggests f/11 is okay on Oly M43 cameras (16MP, 50% crop factor), but by f/16 you are beginning to get diffraction limitations. This is irrespective of what lens you are using. Very interesting.
I noticed that too. I found it interesting it peaked out at f16, whereas f8 was often cited as the break point.

I've not had issues at f8 TBH, and I also bear in mind what the target media is when shooting. Well, if it's known.

I tend to place more emphasis on getting the image I need to, rather than worrying about diffraction.
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Old 18th June 2017
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Re: Diffraction Testing.

Quote:
Originally Posted by Michael Sewell View Post
... I tend to place more emphasis on getting the image I need to, rather than worrying about diffraction.
Absolutely! I'm amused that people consider such minor technical issues while ignoring the basics of producing good quality images...

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Old 18th June 2017
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Re: Diffraction Testing.

We can be certain Robert Capa was more concerned with staying alive than diffraction:
https://www.magnumphotos.com/newsroo...y-omaha-beach/
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Old 18th June 2017
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Re: Diffraction Testing.

True!
Not forgetting McCullin's Nikon that took a bullet for him:


However, it is true that diffraction is a significant issue at f22 (when you're trying to get a shutter speed around 1/15th and, even at ISO64, it's too damn bright and you've forgotten to bring an ND filter).

e.g. have a look at the crowd in this:

Passing traffic1400x1050 sRGB by drmarkf, on Flickr
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