*D 300 F/11 diffraction too limited?*

Started May 16, 2008 | Discussions thread
BasilG Veteran Member • Posts: 7,578
Re: Diffraction and print size

monte12345 wrote:

Diffraction effects are independent of the camera resolution.

Yes, the physical effect is of course resolution-independent, but whether you see it DOES depend on sensor resolution (can't get resolution above the nyquist frequency of the sensor). What you forget to mention is that 375 ll/mm on a DX sensor (which is the lens limit you're citing) corresponds to a 54 MP sensor (this is, unless my calculation is wrong - 375 ll/mm would be 375*16 = 6000 pixels on the short and 375*24 = 9000 pixels on the long side of the image; 54 MP).

Now for some math. BTW, I am basing the theoretical lens resolution
on Nikon's e-line table for resolution versus aperture. Which is as
follows.

f1.0 = 1560 ll/mm . . . 24 x 36 inch
f1.4 = 1072 ll/mm . . . 24 x 36 inch
f2.0 = 750 ll/mm . . . . 24 x 36 inch
f2.8 = 536 ll/mm . . . . 24 x 36 inch
f4.0 = 375 ll/mm . . . . 24 x 36 inch
f5.6 = 268 ll/mm . . . . 16 x 24 inch
f8.0 = 188 ll/mm . . . . 11 x 17 inch
f11 = 136 ll/mm . . . . . 8 x 12 inch
f16 = 94 ll/mm . . . . . . 6 x 9 inch
f22 = 68 ll/mm . . . . . . 4 x 6 inch
f32 = 47 ll/mm . . . . . . 3 x 4 inch
f45 = 32 ll/mm . . . . . . 2 x 3 inch
f64 = 24 ll/mm . . . . . 1.5 x 2 inch

So, keeping in mind that we want to achieve a resolution of 10 ll/mm
on the final print it's now easy to do the math. At f8, because
there are 188 ll/mm available in theory, we have to limit the total
magnification to 18.8 X. For the DX format that means that we
multiply 16mm by 18.8 to determine the vertical dimension of our
final print. (16 x 18.8) 25.4 = 11.84 inches so call it good for an
11 x 17 inch print. Which is how the above table was constructed.
Note, the table stops at 24 x 36 inches for the maximum print size
for one simple reason, even the very best Nikkors can only approach
theory at an aperture of f4.

If you want 10 ll/mm, you need 254 dpi print resolution. Which, with a 12 MP sensor (offering 175 ll/mm), corresponds to a maximum of a 11 x 17 inch print, and indicates that you're diffraction limited approx. from f/8. At apertures larger than f/8, the sensor is limiting (meaning that larger prints than 11 x 17 at 10 ll/mm can't be had anyway), stopped down beyond f/8 or f/11, diffraction is limiting.

BG

Post (hide subjects) Posted by
(unknown member)
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow