Toothwalker wrote:
I don't use my Zeiss lenses as frequently as before, but I recently took the Y/C 21/2.8 and the Milvus 35/1.4 ZE to a foggy forest on Madeira:
I recently acquired a Carl Zeiss 2/50 Makro-Planar ZE. I bought a Vello adapter to use it on my OM-D E-M1MKIII. I haven't had a chance to work on the raw files yet, but here are some jpgs edited with Snapseed. These were captured the day before these spring ephemerals were buried with snow...
"We were slaughtered in this place because we fought against internal tyranny, for freedom and against the foreigner, for the independence of the homeland. We dreamt a free, just and democratic Italy. May our sacrifice and our blood sow the seed and act as warning for generations to come."
Today is Liberation Day in Italy (25 April 1945 - 25 April 2023).
Lenstip review of the same lens states: "The lens doesn't change its focal length and it significantly limits 'focus breathing', a fact that will make video-recording users very happy."
So, there is some discrepancy between what the video shows and what Lenstip reported. I wonder if the assumption that the focal length of the 35/2 AL doesn't change despite the floating element design is true or not.
Anyway, I searched for info concerning focus breathing of my Zeiss ZF.2 35/2 Distagon "Classic".
The-Digital-Picture (here) states that the Zeiss ZE 35/2 (same optics as my ZF.2) "does not exhibit focus breathing - subjects in the frame do not change size as the focus distance is changed. This attribute is especially important to videographers."
I've made a test and the results are in this video.
I feel the Zeiss too has focus breathing, in particular the focal length increases at close focusing distances and - consequently - the angle of view shrinks.
Lenstip review of the same lens states: "The lens doesn't change its focal length and it significantly limits 'focus breathing', a fact that will make video-recording users very happy."
So, there is some discrepancy between what the video shows and what Lenstip reported. I wonder if the assumption that the focal length of the 35/2 AL doesn't change despite the floating element design is true or not.
Anyway, I searched for info concerning focus breathing of my Zeiss ZF.2 35/2 Distagon "Classic".
The-Digital-Picture (here) states that the Zeiss ZE 35/2 (same optics as my ZF.2) "does not exhibit focus breathing - subjects in the frame do not change size as the focus distance is changed. This attribute is especially important to videographers."
I've made a test and the results are in this video.
I feel the Zeiss too has focus breathing, in particular the focal length increases at close focusing distances and - consequently - the angle of view shrinks. ...Show more →
What these videos show is normal behavior for a lens with a fixed focal length. The focal length does not change with the focus distance, but the angle of view does. If the optical design has floating groups with differential focusing, the focal length can change with focus distance. This can either enhance or counteract the effect.
Toothwalker wrote:
What these videos show is normal behavior for a lens with a fixed focal length. The focal length does not change with the focus distance, but the angle of view does. If the optical design has floating groups with differential focusing, the focal length can change with focus distance. This can either enhance or counteract the effect.
Thank you Paul.
Correct me if I'm wrong; you say that the angle of view changes due to magnification effect only (the larger the magnification, the smaller the AoV). Is it correct?
Then, can we infer or not that those videos do show "focus breathing" anyway?
P.S.: I have calculated the AoV along the frame diagonal of my Zeiss 35/2 at infinity (magnification = 0) and at the minimum focus distance (magnification = 0.19).
The equation to calculate the AoV is:
AoV = 2arctg{43/[2F(1+M/P)]}
where 43 is the diagonal of the FF (24x36), F is the focal length of the lens, M the magnification and P the pupil factor.
The pupil factor of the 35/2 I measured is 1.4, and doesn't change significantly from infinity to 0.3 m.
The values are (assuming a constant focal length of 35 mm):
AoV(infinity) = 63°
AoV(0.3m) = 57°
