[i_trax]

We had a little discussion about varifocal vs parfocal zooms and "focus breathing" was mentioned and discussed.
I thought that this phenomenon can occur in varifocal zooms only.
To me , the image size was changing while zooming/focusing,

But , of course , it can also happen in primes as well.

---------- Post added 07-16-21 at 07:53 ----------

That's not what 'focus breathing' means, i_trax.

'Focus Breathing' is a lens term.

It refers to the phenomenon that with an internal zoom, you only get the maximum length (50mm in this case) at infinity.

At any real distance, the focal length is shorter.

For instance, up close, the DFA*70-200 is reported as only being able to achieve 135mm, whatever the markings on the barrel say at the time.

If you follow Youtube camera channels, The Cameraville Guy goes nuts about that DFA for this reason. He thinks we're being cheated.

Weather sealing is obviously easier to design with an internal focus zoom, lets hope the engineers have compensated properly! They set out to make a fast focusing, robust professional lens with the image quality of the rest of the Star series.

I do not have 70-200 so can not test / confirm , so you are saying that 200mm can only be achieve at infinity?
everywhere else you can only get 135mm?
So the outcome of this problem is the image size "breathing" while focusing?

[Serkevan]

We had a little discussion about varifocal vs parfocal zooms and "focus breathing" was mentioned and discussed.
I thought that this phenomenon can occur in varifocal zooms only.
To me , the image size was changing while zooming/focusing,

But , of course , it can also happen in primes as well.

---------- Post added 07-16-21 at 07:53 ----------


I do not have 70-200 so can not test / confirm , so you are saying that 200mm can only be achieve at infinity?
everywhere else you can only get 135mm?
So the outcome of this problem is the image size "breathing" while focusing?

Not "everywhere else" - but the image size decreases as you focus closer, getting to a FL of ~130 mm at minimum focus distance. If you're focused at, say, 5-6 meters, the FL will still be about 170 mm or so (very roughly).

[clackers]

I do not have 70-200 so can not test / confirm , so you are saying that 200mm can only be achieve at infinity?

Correct. And that is the actual optical definition of focal length - at infinity. Nowhere else.

everywhere else you can only get 135mm?

Incorrect.

It happens to all those kinds of zooms. You should hear Tony Northrup prattle on about it.

Obviously it's a sliding scale from around 135mm at MFD to 200mm at infinity. I have no idea if it's linear or whatever. My Tamron 70-200mm and Sigma 150-450 all extend so don't have this internal focus problem.

[Rondec]

We had a little discussion about varifocal vs parfocal zooms and "focus breathing" was mentioned and discussed.
I thought that this phenomenon can occur in varifocal zooms only.
To me , the image size was changing while zooming/focusing,

But , of course , it can also happen in primes as well.

---------- Post added 07-16-21 at 07:53 ----------


I do not have 70-200 so can not test / confirm , so you are saying that 200mm can only be achieve at infinity?
everywhere else you can only get 135mm?
So the outcome of this problem is the image size "breathing" while focusing?

The 70-200 is only 200mm at infinity focus, but it is probably close to 200 mm anywhere focusing past 4 or 5 meters. The issue is when you get into macro distances, the focal length "shortens" and makes it so that even though you can focus down to 1.2 meters, you only get .13x magnification at that point. Most zooms have this to a lesser or greater extent, but it usually isn't as big a deal as reviewers say it is.

[repaap]

This is true what you guys are talking about extending lens barrel. I have 70-200 and I can confirm that. I also have original 16-50 and to me it looks like longer design of new lens reduces a bit the lenght that this new barrel has to travel. So they have taken best out out of both worlds keeping it sturdy but also maintain and even increase close focus performance.

[bdery]

Well, when Ricoh engineers sat around the table, the question of internal vs external zooming came up. They made two virtual models of the 16-50 2.8 , performed optical simulations and manufacturing cost estimates. Turned out the external zoom version had better optical performance both sharpness and chromatic aberrations, corner to corner, it was lighter weight, smaller and cheaper to manufacture. So they decided to go for the external zoom version. Now, if customers can do better than Ricoh engineers, I think they should send their own design and optical simulation results to Ricoh.

Oftentimes, an internal zoom is an external zoom contained inside an enclosure In essence it boils down to total lens size.

Although many times the front element doesn't move for an internal zoom, but that's not a requirement per se.

[biz-engineer]

Although many times the front element doesn't move for an internal zoom, but that's not a requirement per se.

Whether the front element moves or not probably has an impact on optical properties of the lens. All macros lenses that I'm aware of focus with moving front group, there must be a good reason.

[stevebrot]

The rumors forum discovers focus breathing and the sky is falling. I had not owned my Sigma 17-70/2.8-4 (C) more than a couple of days before I realized that working distance for portraits was a little short for 70mm, say closer to 50mm. That is how internal focus works, by decreasing the effective focal length.


Steve

[phoebus]

SRS in UK have 30th July as expected arrival date for the DA* 16-50 PLM.

Pentax HD DA 16-50mm F2.8 ED PLM AW Lens - Pre-order Deposit

If that really happens, Ricoh will have bettered their August availability

[Rondec]

The rumors forum discovers focus breathing and the sky is falling. I had not owned my Sigma 17-70/2.8-4 (C) more than a couple of days before I realized that working distance for portraits was a little short for 70mm, say closer to 50mm. That is how internal focus works, by decreasing the effective focal length.


Steve

I guess people need something to talk about, but why there is so much focus on focus breathing is beyond me. The majority of zooms have some of it. It doesn't negative other good aspects that they have. I mostly look at the maximum magnification as a surrogate for this and it is 0.24x with the 16-50 PLM. That's good enough, I think. The Nikkor 17-55 f2.8 has a max magnification of 0.2x and Canon's 17-55 f2.8 has a max magnification 0.17x.

Clearly none of them are macro lenses and all of them having more shortening with close focus than Pentax's 16-50.

[zapp]

DFA 24-70 is already sold. Just need a deal on K3iii with 16-50.
11-18 is also a great Pentax lens. Pentax really has a plan here. The upcoming 21 will be nice on APAC and ff and we are still waiting for a large aperture wide angle.

[Ishpuini]

SRS in UK have 30th July as expected arrival date for the DA* 16-50 PLM.



Pentax HD DA 16-50mm F2.8 ED PLM AW Lens - Pre-order Deposit



If that really happens, Ricoh will have bettered their August availability

Time to send a mail to my B&M store then...

[Nuftur]

I am happy that this lens appears, although I will not buy it (because I use FF) as it shows, that Pentax is still investing.

BR Nuftur

[manishved]

This is good news indeed from Pentax....

[reh321]

Oftentimes, an internal zoom is an external zoom contained inside an enclosure In essence it boils down to total lens size.

Isn't weather-sealing more reliable on internally zooming lenses, because there are fewer places where water could get in??