Addendum to Tutorials Page: Understanding the Diffraction Limit, Part 2

[McQ]

There's now a second page to the existing diffraction tutorial. The new page is located at:

Understanding Diffraction, Part 2: Resolution, Color & Micro-Contrast

It's reasonably technical, but aims to address why there's so many different opinions on when diffraction will become visible with a given sensor size/resolution and f-stop. The article incorporates issues relating to Bayer sensors, the color content of an image, extinction vs artifact-free resolution, etc.

It also provides a new calculator that can be played with to see how f-stop affects image properties for different sensor sizes and megapixel counts. As always, actual results will depend on the particular lens, but overall I think you'll find that it agrees pretty well with how images tend to appear.

Finally, please forgive the slight redundancy with the earlier tutorial; this is only there so that the page can stand on it's own if needed.

As usual, any comments/feedback/critiques/etc are all appreciated.

[Colin Southern]

Hi Sean,

Change "location" to "aperture" in line 3 of the intro paragraph?

Possibly change calculator to make full frame sensor choice a bit more obvious ("Full Frame")?

[McQ]

Change "location" to "aperture" in line 3 of the intro paragraph?

Possibly change calculator to make full frame sensor choice a bit more obvious ("Full Frame")?

Thanks, these parts have been updated.

[Andy]

No mention of how magnification will effect things? (the diffraction limit goes down as magnification goes up but it probably doesn't matter unless you're into macro)

[McQ]

No mention of how magnification will effect things? (the diffraction limit goes down as magnification goes up but it probably doesn't matter unless you're into macro)

Hi Andy -- thanks for the feedback. The diffraction limit remains the same regardless of magnification. However, what does change is the effective aperture. Perhaps that's what you have in mind? There's more on diffraction and macro here: macro lenses: magnification, depth of field & effective f-stop.

[arith]

Very interesting read; I usually go on LW/PH figures for the lens camera combination and find for instance with my zoom I'm best between f5.6-f8, however after reading your tutorial realised these are calculated from black and white charts and so apply for luminence which is mostly influenced by green.

However as Colin stated elsewhere diffraction is a gradual thing and I have used f16 where I wanted the hyperfocal distance to be as close as possible and it didn't look too bad to me, but in future if I'm taking a pic of something with red or blue detail I will try to keep the f-stop wider than f7.1.

Thankyou for a very clear and easily readable tutorial.