NikonGear'23

Gear Talk => Lens Talk => Topic started by: frederikboving on October 04, 2021, 14:37:08

Title: What is this? Coma? Comatic aberration?
Post by: frederikboving on October 04, 2021, 14:37:08

Comes with the Nikon 50mm AF 1.4D + the same in 1.8G.
I tried to stress the lens to produce some coma, and the attached is what I got.
Some long "arms" stretching north and south from the center of the light spot.
This is the extreme corner of the frame you see in the image. Snipe from LR.

Title: Re: What is this? Coma? Comatic aberration?
Post by: Akira on October 04, 2021, 14:54:39

This is an illustrative example to explain how coma looks like.  :)

Title: Re: What is this? Coma? Comatic aberration?
Post by: frederikboving on October 04, 2021, 15:42:50

I thought coma would point to the center of the frame?

Title: Re: What is this? Coma? Comatic aberration?
Post by: Airy on October 04, 2021, 16:19:45

Indeed. These must be crops from the lower left corner. The two "wings" point away from the center, and are arranged symetrically around the radius.

Title: Re: What is this? Coma? Comatic aberration?
Post by: Akira on October 04, 2021, 20:44:48

Quote from: frederikboving on October 04, 2021, 15:42:50

I thought coma would point to the center of the frame?

If I understand correctly, the direction of the coma will depend on the balance of the correction of the related aberrations.

Title: Re: What is this? Coma? Comatic aberration?
Post by: Birna Rørslett on October 05, 2021, 08:12:14

Pure coma, without much chromatic aberrations included.