Author Topic: micro-nikkor Z  (Read 2261 times)

Erik Lund

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Re: micro-nikkor Z
« Reply #105 on: June 10, 2021, 09:31:06 »
We discuss two topics now?
Change in focal length and focus breathing?

I put my AIS 105/4 micro on camera and this lens has focus breathing (I can see that even hand hold).
But I think that is quite obvious why it has focus breathing. It would need a change in focal length during focusing to avoid that like the cine lens "prime" which also zooms a bit when it is focused?

Focus breathing is a term mostly used around shooting video and film as several has commented by now.
IMHO It covers very well the issue here by giving non video/film photographers an visual guide to what is occurring with the visual impact and working distance when using an IF lens that changes focal length as it is focused, especially in the micro macro range.Sorry if you find it confusing. That was not the intension.

Erik Lund

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Re: micro-nikkor Z
« Reply #106 on: June 10, 2021, 10:57:14 »
It was just that a "unit-focus" lens does not prevent focus breathing?

Birna Rørslett

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Re: micro-nikkor Z
« Reply #107 on: June 10, 2021, 11:48:57 »
Depends on what you mean by "breathing".

A unit-focusing lens changes magnification of the subject, not (directly) the angle of view. However, being unit-focusing means the camera stand-point has to move to get an altered magnification of the *same* subject. This of course implies an altered background as well. And a new perspective.

To clarify: this design class will allow you to trim focus precisely largely without changes in the framing. One uses the same principle in focus stacking, but depending on the stack depth, framing will alter as the camera/lens moves along a rail.

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Re: micro-nikkor Z
« Reply #108 on: June 10, 2021, 12:01:48 »
Yes, I also regard change of magnification as "focus breathing".

Birna Rørslett

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Re: micro-nikkor Z
« Reply #109 on: June 10, 2021, 12:11:01 »
Well, then the concept has lost any meaning.

If I want to depict something bigger, I need to move closer with a unit-focusing lens. Angle of view does not change, but perspective does, and so does background. Other lenses allow the camera to stay put. Thus in the latter case, perspective stays the same, however angle of view has to change since magnification changes. Still other optical designs combine the responses differently.

I was immensely annoyed by the focus breathing of the AFS 105/2.8 VR: with the camera on a tripod, I could not refocus ie. make tiny adjustments to the focused plane, without changing the entire view, or move the tripod. For close-ups that was a deal breaker.

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Re: micro-nikkor Z
« Reply #110 on: June 10, 2021, 12:42:31 »
Ok. My definition of a "non focus breathing" lens was a lens that could be used as a prof. cine lens.
So a lens where angle of view is not changed when focused from close range to infinity......like demonstrated in the video I had a link to.....
But I can now see why I got confused.....

Ilkka Nissilä

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Re: micro-nikkor Z
« Reply #111 on: June 10, 2021, 13:13:22 »
Ok. My definition of a "non focus breathing" lens was a lens that could be used as a prof. cine lens.
So a lens where angle of view is not changed when focused from close range to infinity......like demonstrated in the video I had a link to.....
But I can now see why I got confused.....

Right, that is the most commonly used definition the way I have understood it. I.e. angle of view stays constant as the focus is changed.

Anyway, what is not important is the exact meaning of specific terms but to use them in such a way that everyone can understand the meaning of those terms in the context of the discussion. I.e., when using a term, explain what you mean by it in the beginning.

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Re: micro-nikkor Z
« Reply #112 on: June 10, 2021, 15:18:12 »
You are right!
I had the assumption that if "anything moves" during focusing it was "focus breathing".......call it change in magnification, angle of view.....or whatever.

But I can now see that it is more complex than that :-)

simsurace

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Re: micro-nikkor Z
« Reply #113 on: June 10, 2021, 15:44:39 »
If I want to depict something bigger, I need to move closer with a unit-focusing lens. Angle of view does not change, but perspective does, and so does background.

Now I'm getting confused as well  :D

My understanding is that for large extensions (compared to the focal length), the effective (as opposed to the nominal one which usually refers to the AOV at infinity) angle of view narrows with a unit-focusing lens. Thus a unit-focusing lens will 'breathe' significantly at closer range. It is sometimes hard to see this because the background blurs so much, but one should look at the centers of the blur circles moving outward. In other words, cine lenses that are not supposed to breathe cannot be unit focusing. Basically in a non-breathing lens, the optical center of the lens has to remain stationary with respect to the sensor plane as the lens is focused back and forth. Which implies that the focal length in a non-breathing lens has to shorten as the lens is focused closer.
Simone Carlo Surace
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Re: micro-nikkor Z
« Reply #114 on: June 10, 2021, 22:49:44 »
There is a small article here about "focus-breathing":

https://photographylife.com/focus-breathing

They use Nikkors as examples and it seems focus-breathing has been taking care of in the Z-lenses.

simsurace

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Re: micro-nikkor Z
« Reply #115 on: June 11, 2021, 00:07:45 »
Thanks for reminding me of that article, which I read back when it came out. Unfortunately that article may cause more confusion, but there are a few comments below the article that are actually worth reading.

E.g. the comment by Kenneth Almquist, which confirms my guess above, particularly this part:

Quote
Focusing works differently on cinema lenses than it does on photographic lenses. On a cinema lens, changing the focus changes the focal length of the lens while keeping the optical center (and thus the field of view) constant. If there is a 50mm macro cinema lens out there, it will have a focal length of 50mm when focused at infinity and a focal length of 25mm when focused an at object close enough to get a 1:1 reproduction ratio.

Simone Carlo Surace
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Erik Lund

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Re: micro-nikkor Z
« Reply #116 on: June 11, 2021, 08:50:40 »
There is a small article here about "focus-breathing":

https://photographylife.com/focus-breathing

They use Nikkors as examples and it seems focus-breathing has been taking care of in the Z-lenses.
Yes, some of the Nikkor Z mount lenses, but not all of them.
Erik Lund