Diffraction and ultimate FF pixel count

Started 3 weeks ago | Discussions thread
ForumParentFirstPrevious
Flat view
JimKasson
JimKasson Forum Pro • Posts: 25,523
Diffraction and ultimate FF pixel count
12

The announcement of the 61 MP a7RIV has reignited the oft-heard arguments that photographers don't need any more resolution in their cameras than they have now. There is a variation on this argument that says that a reason why greater resolution brings no benefits is diffraction.

It is undeniably true that there are pixel pitches and apertures beyond which diffraction will limit resolution. A relevant question is: "What pitches and what apertures?"

I constructed a spreadsheet to answer that question.

I assumed 555 nm (green, mid-visible spectrum) light, and computed the Sparrow distance, the place where the sum of two Airy disks develops a flat top. Then I calculated the number of Sparrow distances that would span a FF sensor horizontally and vertically. I multiplied those two together to get how many MP a FF sensor would have to have to sample a diffraction-limited lens at the Sparrow distance. That's the column labeled "MP".

Finally, to get adequate sampling of the diffraction-limited image by the red and blue pixels of a Bayer color filter array camera, I created the far-right column.

Consumer diffraction-limited lenses are thin on the ground, but these numbers serve as  an indication of the physical limits, absent techniques such as are used in making semiconductors and in microscopy.

Jim

-- hide signature --
 JimKasson's gear list:JimKasson's gear list
Nikon D5 Fujifilm GFX 50S Sony a9 Sony a7R III Sony a7 III +5 more
ForumParentFirstPrevious
Flat view
Post (hide subjects) Posted by
ForumParentFirstPrevious
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow