DPReview.com is closing April 10th - Find out more

Anybody owned, or used the Canon 400mm f/4 DO IS II on....

Started 4 weeks ago | Discussions thread
Chris Wolfgram
OP Chris Wolfgram Veteran Member • Posts: 6,619
Re: Anybody owned, or used the Canon 400mm f/4 DO IS II on....

John Sheehy wrote:

ThrillaMozilla wrote:

The aperture is 400mm/4 = 100 mm, vs. 71 mm for the 800/11. Thus, lower magnification, but twice the light captured per duck. 71% of the shot noise, and theoretically resolves details 71% as large, assuming diffraction-limited.

I haven't done a well-controlled comparison of the f-ratios on the 400DO II, but f/5.6 is not any sharper than f/4 in my experience, so aberration seems to be well-controlled.

However, under very high magnification, like with a 12MP 1/2.3" Pentax Q on the lens, it has pixel-level detail and even slight aliasing for a very narrow range of distances, as thin as a sheet of paper, and this is blended with a softer point-spread function that lowers high-frequency contrast. IOW, the total PSF seems to be like this:

o

oo

oo

ooooo <- this part is capable of aliasing with the Q.

oo

oo

o

Many DSLR lenses don't have that central spike.

This sounds important.... Wish I was smart enough to understand it 😀

-- hide signature --

Photos are my paintings. The camera is my brush.
Website
www.LightInEveryCorner.com
DPreview gallery; http://www.dpreview.com/galleries/5075216809
No time or attention given for negativity or trolls.

 Chris Wolfgram's gear list:Chris Wolfgram's gear list
Canon EOS R7 Canon EF 16-35mm F2.8L II USM Canon EF 24-70mm F2.8L II USM Canon RF 600mm F11 IS STM Canon RF 800mm F11 IS STM +1 more
Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow