Part 2 -> 52 mp and new EF lens line confirmed by Canon

Started Jan 9, 2015 | Discussions thread
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Rick Knepper Forum Pro • Posts: 14,904
Part 2 -> 52 mp and new EF lens line confirmed by Canon
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Rick Knepper wrote:

Schmegg, after re-assessing the article and Sean's response to me, go back to the CiC's diffraction calculator, click Show Advanced, input various resolutions, then tell me what you think.

Yes Rick - I've read all the Cambridge stuff ages ago - and probably forgotten some of it too by now!

But what I took from it is very much what Sean began with ...

"In the traditional sense, the megapixel count does not determine the diffraction limited aperture, since one is normally only concerned with whether diffraction related softness shows up based on a given print size."

To me, this is the single most sensible way to consider diffraction effects. Why should I care about 100% pixel level sharpness if I never view my final images at that size? Makes no sense to me at all and I truly believe that considering it any other way is purely the domain of the pixel peeper who is not particularly interested in the final product but rather in the 100% peeper view.

BTW - this is precisely the same as normalising for noise or DR so that sensible, useful comparisons can be made between different pixel count/density sensors.

The problem with picking out the 'facts' one agrees with or want to agree with and ignoring the rest of the issue (general life advice not constrained to just photography) is that one becomes tunnel-visioned and makes discussions difficult at best with others with different needs than one's own.

Schmegg, do you ever crop?

So, if I wrongly implied (therefore accused) you of being disingenuous, I apologize.

As for someone injecting a link between sensor resolution and diffraction into the conversation, I cannot take responsibility for that. Personally, I steer clear of this notion because I have found myself in more than one brouhaha about this 'issue' over the years and the notion that resolution does not affect diffraction is solidly entrenched in folks' understanding (for good reason). However, they refuse to listen to any other ideas on the subject.

Read carefully, random thoughts and events:

During the last brouhaha, someone provided historical context for why the opposite notion, i.e. resolution does affect diffraction - at least in the results of the site's diffraction calculator, had gotten so much traction across the Internet. In 2009, Cambridge in Colour's diffraction calculator clearly had input for resolution and if the right input was set to On, resolution made all kinds of difference.

Sometime between 2009 and the present, Cambridge in Colour redesigned their website and among the changes, simplified their diffraction calculator with only a link for Show Advanced so that the field for resolution does not show in the simplified version of the calculator.

Here's that article:

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

It seems that pixel size does have some affect on the visibility of diffraction:

Excerpt from article:

As a result of the sensor's anti-aliasing filter (and the Rayleigh criterion above), an airy disk can have a diameter of about 2-3 pixels before diffraction limits resolution (assuming an otherwise perfect lens). However, diffraction will likely have a visual impact prior to reaching this diameter.

As two examples, the Canon EOS 20D begins to show diffraction at around f/11, whereas the Canon PowerShot G6 begins to show its effects at only about f/5.6. On the other hand, the Canon G6 does not require apertures as small as the 20D in order to achieve the same depth of field (due to its much smaller sensor size).

After my first brouhaha about diffraction on DPR (where I held the opinion that diffraction was linked to resolution), I went to Cambridge's forum and asked the following question and got this answer:

http://www.cambridgeincolour.com/forums/thread869.htm

For those too 'busy' to click the link, here's Sean's answer:

"In the traditional sense, the megapixel count does not determine the diffraction limited aperture, since one is normally only concerned with whether diffraction related softness shows up based on a given print size. Whether the camera is 10 or 100 megapixels will not change the diffraction limited aperture for a sharp 8x10 inch print, for example. This is why the "Set Circle of Confusion = Twice Pixel Size?" is set to off by default, since it means that the CoC is defined only by the output print size, as follows:

An acceptably sharp circle of confusion is loosely defined as one which would go unnoticed when enlarged to a standard 8x10 inch print, and observed from a standard viewing distance of about 1 foot. At this viewing distance and print size, lens/camera manufactures assume a circle of confusion is negligible if it is no larger than 0.01 inches at this size.
(Taken from this site's tutorial on Depth of Field)

However, nowadays people are also concerned with whether their camera's megapixel count or its optical resolution is the limiting factor. In other words: when your image is viewed at 100% on a monitor, will it appear soft due to diffraction, or is there still more detail to be obtained by going to a higher megapixel count (for the given aperture setting)? This is why the "Set Circle of Confusion = Twice Pixel Size?" was made available. When it is checked, it defines a custom size for the CoC based on (twice) the absolute size of each pixel (using the input boxes with gray text labels; otherwise the boxes with gray text are not required). In this case, as the number of megapixels increase (for a given sensor size), the size of the CoC decreases, so the diffraction limit is indeed related to the number of megapixels.

The aim with the "Set CoC = Twice Pixel Size" setting was to settle a lot of the debates I was seeing on the forums relating to whether and when more megapixels actually improves image detail. There were a lot of people arguing that diffraction effects would mean that cameras with more than X megapixels were often times not producing any more detail.

Hope this clears things up. I am always interested in feedback regarding real-world use/interpretation of this calculator. Please let me know if there's still any confusion.

PS: One thing that I should really add to that page is a detailed calculator description/directions page as a pop-up window... "

Schmegg, after re-assessing the article and Sean's response to me, go back to the CiC's diffraction calculator, click Show Advanced, input various resolutions, then tell me what you think.

 Rick Knepper's gear list:Rick Knepper's gear list
Pentax 645Z Canon EOS 5DS R Fujifilm GFX 50S +2 more
Canon EOS 20D Panasonic Lumix DMC-G6
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