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Macro lens without focus breathing

 
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Kashim



Joined: 18 Dec 2014
Posts: 32

PostPosted: Fri Apr 03, 2015 4:12 pm    Post subject: Macro lens without focus breathing Reply with quote

Are there any macro lenses out there that don't suffer from focus breathing? The only lens I've seen/owned without focus breathing is the Canon 55-250mm STM lens. From what I understand, STM lenses are designed for video where focus breathing can be very annoying.

I was using the 250mm STM lens with a Raynox 150 and it wasn't bad (for focus stacking), but I would like to find a true macro lens without focus breathing. These STM lenses use rear focusing, whereas all the macro lenses I've seen either focus by moving the front element (thereby extending the lens) or they use internal focusing.

Are there no macro lenses out there that use rear focusing or some other way to eliminate focus breathing?
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elf



Joined: 18 Nov 2007
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PostPosted: Fri Apr 03, 2015 6:58 pm    Post subject: Reply with quote

Using a bellows would probably cure the problem.
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ChrisR
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PostPosted: Fri Apr 03, 2015 7:31 pm    Post subject: Reply with quote

Old Micro Nikkor 55mm f/2.8 is one..
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Chris S.
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PostPosted: Fri Apr 03, 2015 8:14 pm    Post subject: Reply with quote

ChrisR wrote:
Old Micro Nikkor 55mm f/2.8 is one..

That makes sense, since it was designed with copy-stand work in mind, for which local length changes would be very annoying. Also, being of fairly short focal length, the helicoid doesn't have to be so very gargantuan.

Kashim, the excuse we hear for the existence of breathing in macro lenses is to keep the focusing mechanisms from being overly large and complex. (Remember that the longer the focal length of the lens, the farther it needs to be from the sensor at 1:1--so this is a bigger issue with longer focal lengths.) Personally, I might happily choose a bigger, more expensive macro lens that didn't breathe.

Which gets us to Elf's point--you can use a bellows instead of the focusing helicoid (though how well any given lens will work in this regime is something you would want to test). And as you may be aware, there have been some very good macro lenses made that have no provision for focus, and are designed to be used on a bellows. These would be sourced mainly on the used market.

But you've made it clear in another thread that you want an automated iris, which is something you won't get on a bellows.

--Chris
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rjlittlefield
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PostPosted: Fri Apr 03, 2015 9:42 pm    Post subject: Reply with quote

I understand the term "focus breathing" to mean that angle of view changes along with focus.

If this is the same thing that you guys mean, and unless I've missed something fundamental, then using a bellows will definitely not solve the problem.

To get rid of focus breathing, you need a lens that shortens its focal length as it focuses closer, and further, does that in a carefully coordinated way so that the rear principal plane stays a fixed distance from the sensor. That's a very specific design requirement that requires careful integration all the way back to the camera mount.

--Rik
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Chris S.
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PostPosted: Fri Apr 03, 2015 10:18 pm    Post subject: Reply with quote

Rik, what I want is not to keep the angle of view constant, but to keep the field of view constant.

--Chris
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rjlittlefield
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PostPosted: Sat Apr 04, 2015 12:03 am    Post subject: Reply with quote

Chris S. wrote:
what I want is not to keep the angle of view constant, but to keep the field of view constant.

When I Google "focus breathing", the first half-dozen hits all talk about it in terms of angle of view. But I think you're talking about the same thing. You want to position the subject so as to see a certain field of view, even if it's out of focus, then adjust focus without changing the field of view, that is, without having the image get bigger or smaller.

Either way we think about it -- angle of view or field of view -- I'm completely missing how using a bellows is going to meet this requirement.

Can you explain in more detail what adjustments you're thinking of, to make this work?

--Rik
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bobfriedman



Joined: 28 Jul 2009
Posts: 181

PostPosted: Sat Apr 04, 2015 8:02 am    Post subject: Reply with quote

the discontinued AF Micro-Nikkor 70-180mm f/4.5-5.6D was the only zoom macro lens and it doesn't breath even with zoom if memory serves me.
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ChrisR
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PostPosted: Sat Apr 04, 2015 8:17 am    Post subject: Reply with quote

I'm not sure about that - I'll have to try it! It does get physically longer at close focus though. It's certainly nice to use.

I'm wondering what Kashim meant when by the "breathing" term. Was it only "not changing FL"?
Internally Focus on a macro lens is also desirable; I don't know of an IF lens which keeps a constant FL, but there may be some.
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rjlittlefield
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PostPosted: Sat Apr 04, 2015 10:50 am    Post subject: Reply with quote

I hate to sound pedantic, but if you want to avoid changing image size with focus, then keeping a constant FL is exactly the wrong thing to do.

There is some discussion HERE that may be helpful.

--Rik
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ChrisR
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PostPosted: Sat Apr 04, 2015 4:35 pm    Post subject: Reply with quote

Sure, but "breathing" is generally criticised because the FL changes with focus.
The only lenses I can think of which hold it, are telecentric - rather thin on the ground.

Kashim come back!!
I assume your complaint about breathing is with eg a 100mm macro lens which becomes 70mm at close focus, so the working distance is less than you would like. Is that right?
I was tempted by a 200mm Micro Nikkor, but put off because it's a heavy breather.
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Kashim



Joined: 18 Dec 2014
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PostPosted: Sat Apr 04, 2015 5:30 pm    Post subject: Reply with quote

Chris S. wrote:
But you've made it clear in another thread that you want an automated iris, which is something you won't get on a bellows.

Yes, I do want automatic aperture control for my general use macro lenses, but I'm not against using a fully manual lens for those times when I actually come across a subject that isn't in a hurry to get away.

ChrisR wrote:
I'm wondering what Kashim meant when by the "breathing" term. Was it only "not changing FL"?
Internally Focus on a macro lens is also desirable; I don't know of an IF lens which keeps a constant FL, but there may be some.

The link posted by rjlittlefield is pretty much what I was talking about. With my Canon 55-250mm STM lens what you see in the frame stays exactly the same as you move the area in focus back and forth, because this lens doesn't suffer form focus breathing. With any other lens, if I move the area in focus away, everything in the frame "shrinks" slightly, and as I move the area in focus closer, everything "expands" slightly. Sorry, that's the best way I can describe it.

ChrisR wrote:
I assume your complaint about breathing is with eg a 100mm macro lens which becomes 70mm at close focus, so the working distance is less than you would like. Is that right?

Nah, I don't care about the working distance changing due to focus breathing. The effect isn't too pronounced to be an issue in most situations.

The main reason I wanted a macro lens without focus breathing is for doing focus stacks. I find it very useful in that situation and it helps tools like Zerene produce a better result. Doing stacks with a lens that does have focus breathing produces some distortions in the stack because the field/angle of view changes between shots. I believe the phrase was "parallax distortion" to describe this effect.

Here's an example image I took last year. It's a focus stack of 9 images, taken with a Canon 55-250mm STM lens + Rayonx 150. It came out pretty good on the first attempt in Zerene, because I didn't have to contend with any distortions caused by focus breathing.
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rjlittlefield
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PostPosted: Sun Apr 05, 2015 12:06 am    Post subject: Reply with quote

Kashim wrote:
The main reason I wanted a macro lens without focus breathing is for doing focus stacks. I find it very useful in that situation and it helps tools like Zerene produce a better result. Doing stacks with a lens that does have focus breathing produces some distortions in the stack because the field/angle of view changes between shots. I believe the phrase was "parallax distortion" to describe this effect.

There are at least three different things going on here. I think it's important to keep them clearly separated, and to correct some common misconceptions that I'm pretty sure I see in these words.

1. Focus breathing in the sense of changing field/angle of view does not introduce distortions in the stack and has only very minor effects on the quality of output. Zerene Stacker and every other decent stacking software can perfectly compensate for the simple changes of image scale that are caused by focus breathing. At the very worst, there is some reduction in the effective pixel count at the "wide" end of the stack, because that end essentially gets cropped to match the "narrow end". In addition there may be some slight softening of the image due to subpixel interpolation while correcting for the scale differences. Those can be made invisible by using one of the higher order Lanczos interpolation methods.

2. A lens that does not have significant focus breathing definitely is more convenient to use for focus stacking. That's because less attention is required to avoid a framing error that will cut off part of the subject at the "narrow" end of the stack.

3. What can/will cause degraded stacking is if the entrance pupil moves too far forward or backward as the stack is being shot. The issue is discussed in my page at http://zerenesystems.com/cms/stacker/docs/troubleshooting/ringversusrail. This behavior varies from lens to lens and is not tied in any simple way to focus breathing. As an example, using a fixed lens on bellows that is focus-stepped by changing the rear extension is perfect from the standpoint of having zero entrance pupil movement, but it exhibits about the worst focus breathing of any optical setup you're likely to use.

Quote:
Here's an example image I took last year. It's a focus stack of 9 images, taken with a Canon 55-250mm STM lens + Rayonx 150. It came out pretty good on the first attempt in Zerene, because I didn't have to contend with any distortions caused by focus breathing.

That's an excellent image, but it's only one example so generalizations are risky. If in fact the Canon 55-250 STM lens + Raynox 150 is particularly good for focus stacking in general, that will be because the entrance pupil stays in one place, not because of its lack of focus breathing. Quite frankly, I suspect that entirely different factors were responsible for the success of that particular stack, most likely a lack of movement of the flower and fly while the stack was shot, perhaps combined with the almost complete lack of background detail due to extreme OOF and smooth bokeh. Based on my own experiences, I would expect essentially perfect results from any lens and any focusing method for a scene of that nature, in the absence of subject movement.

--Rik
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