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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 27 Oct 2014 (Monday) 11:10
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Parfocal zoom

 
decisivemoment
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Oct 27, 2014 11:10 |  #1

I would like to know if the following two canon lenses are parfocal or not.

1. EF-S 18-55 mm 1:3.5-5.6 IS II

2. EF-S 55-250 mm 1:4-5.6 IS II




  
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MattPharmD
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Oct 27, 2014 13:43 |  #2

nope.
AFAIK, the only canon lenses that are parfocal are the cinema lenses.


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DoughnutPhoto
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Oct 27, 2014 13:48 |  #3

decisivemoment wrote in post #17235595 (external link)
I would like to know if the following two canon lenses are parfocal or not.

1. EF-S 18-55 mm 1:3.5-5.6 IS II

2. EF-S 55-250 mm 1:4-5.6 IS II

"A parfocal lens is a lens that stays in focus when magnification/focal length is changed."

You're mentioning two consumer lenses which have been designed with consumer budget in mind. Building a parfocal zoom (rather than a varifocal zoom which you have to re-focus after zooming) is expensive as it restricts other design choices. I find it unlikely that a consumer zoom would be parfocal.

I did find: "Parfocal zooms in the Canon EF lens line-up are essentially limited to the fixed-aperture L-series categories and front-focusing zoom lenses."

I don't know if I can link to another forum here, but there is a list on another forum if you google "Parfocal Canon Lens".

You can also just pop down to the store and try them out for yourself.

Why are you searching for a parfocal lens? Any special purpose in mind?


Canon 5d, 60d, 17-40mm L, 30mm Art, 50mm, 85mm

  
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SkipD
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Oct 27, 2014 17:12 |  #4

DoughnutPhoto wrote in post #17235935 (external link)
You're mentioning two consumer lenses which have been designed with consumer budget in mind. Building a parfocal zoom (rather than a varifocal zoom which you have to re-focus after zooming) is expensive as it restricts other design choices. I find it unlikely that a consumer zoom would be parfocal.

I have three "L" class Canon zoom lenses and none of them are parfocal. None of the Canon zoom lenses belonging to others (I don't have a list) were parfocal either.


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gjl711
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Oct 27, 2014 17:23 |  #5

MattPharmD wrote in post #17235926 (external link)
nope.
AFAIK, the only canon lenses that are parfocal are the cinema lenses.

There are a few lenses out there that are parfocal. I remember Chuck W. provided a list a while back. If I remember the 70-200s were on there and the 75-300s as well. There were a few more, I think the 17-40 or 16-35 was on the list.


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SkipD
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Oct 27, 2014 21:04 |  #6

gjl711 wrote in post #17236325 (external link)
There are a few lenses out there that are parfocal. I remember Chuck W. provided a list a while back. If I remember the 70-200s were on there and the 75-300s as well. There were a few more, I think the 17-40 or 16-35 was on the list.

My original version Canon 70-200 f/2.8L IS is definitely NOT parfocal. Neither is my original version 16-35 f/2.8L or my original version 24-70 f/2.8L.


Skip Douglas
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gonzogolf
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Oct 27, 2014 21:06 |  #7

24-105 is on the list.




  
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MattPharmD
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Oct 28, 2014 08:19 |  #8

gonzogolf wrote in post #17236704 (external link)
24-105 is on the list.

The 24-105 I used was not parfocal.

The difference is between practically parfocal and actually parfocal.

Seems that several canon L zooms are so close, that under most conditions they seem parfocal (again, something is in focus at 24mm and 105mm without changing focus).

Seems I was wrong, I believe the cinema lenses are the only ones canon claims are parfocal. Roger has a much shorter list here...
http://www.lensrentals​.com …/photo-lenses-for-video/4 (external link)


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amfoto1
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Oct 28, 2014 10:54 |  #9

It's a ten + year old list now, but the following from Canon's Chuck Westfall is the best info we've got...

"Parfocal" means that a zoom lens will not change focus as the focal length of the lens is changed. This is some more information provided by the invaluable Chuck Westfall of Canon US.

Parfocal zooms in the Canon EF lens line-up are essentially limited to the fixed-aperture L-series category and front-focusing zoom lenses.

The current products include:

* EF 16-35mm f/2.8L USM
* EF 17-40mm f/4L USM
* EF 24-70mm f/2.8L USM
* EF 70-200mm f/2.8L USM
* EF 70-200mm f/2.8L IS USM
* EF 70-200mm f/4L USM
* EF 75-300mm f/4-5.6 IS USM
* EF 75-300mm f/4-5.6 III USM
* EF 75-300mm f/4-5.6 III
* EF 90-300mm f/4.5-5.6 USM
* EF 90-300mm f/4.5-5.6

Discontinued lenses in this category include:

* EF 17-35mm f/2.8L USM
* EF 20-35mm f/2.8L
* EF 28-70mm f/2.8L USM
* EF 28-80mm f/2.8-4L USM
* EF 50-200mm f/3.5-4.5 USM
* EF 50-200mm f/3.5-4.5
* EF 70-210mm f/4
* EF 75-300mm f/4-5.6 II USM
* EF 75-300mm f/4-5.6 II
* EF 75-300mm f/4-5.6 USM
* EF 75-300mm f/4-5.6
* EF 80-200mm f/2.8L
* EF 100-300mm f/5.6L
* EF 100-300mm f/5.6

EF zoom lenses with Super Inner Cam focusing, which include most of the non-L zooms introduced from 1990 onwards as well as the EF 35-350mm f/3.5-5.6L USM and the EF 100-400mm f/4.5-5.6L IS USM, are not parfocal.

This information was original posted on the Rob Galbraith Forums on 29 May '03

There's been some discussion about some of the above listed parfocal lenses being "nearly" parfocal and not "truly" parfocal.


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Brian_R
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Oct 28, 2014 11:47 |  #10

MattPharmD wrote in post #17235926 (external link)
nope.
AFAIK, the only canon lenses that are parfocal are the cinema lenses.

this^

and any lens that is manufactured for video cameras or permanentaly mounted on a video such as broadcast cameras that are 1/3" or 2/3" sensor size. well that are actually parfocal.




  
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SkipD
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Oct 28, 2014 12:38 |  #11

amfoto1 wrote in post #17237587 (external link)
There's been some discussion about some of the above listed parfocal lenses being "nearly" parfocal and not "truly" parfocal.

That's absolutely the case for the three lenses that I have (and all are in the list).


Skip Douglas
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ejenner
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Oct 28, 2014 13:47 as a reply to  @ SkipD's post |  #12

I wonder if those listed are parfocal when focused at infinity? I think the 17-40 might have been pretty darn close if that is the restriction. At closer distances, definitely not.


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Keyan
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Oct 28, 2014 18:13 |  #13

So, the STM lenses (I think only when paired with certain bodies but could be wrong) use the STM drive to actually adjust the focus while the zoom ring is turned and remain in focus. A cute technological fix to a complex optics problem.


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Parfocal zoom
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