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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses
Thread started 07 May 2010 (Friday) 13:04
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Difference between parfocal and varifocal

 
phil_5
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May 07, 2010 13:04 |  #1

How do I tell which of my lenses are parfocal and which are varifocal? New terminologies to me.
Thank You




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egordon99
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May 07, 2010 13:07 |  #2

What lenses you own?




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kitacanon
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May 07, 2010 13:11 |  #3

If your shot is out of focus AFTER you zoom then that is a varifocal lens...
...if the image stays in focus after you zoom then it's a parfocal lens....

Most AF zooms are the former so be careful to focus AFTER you zoom to ensure that the shot (stays) is in focus....


My Canon kit 30D/450D/s90; Canon lenses 50/1.8MKI, 18-55 IS, 35/2, 28-105/3.5-4.5, and 70-210/3.5-4.5....The Nikon kit: D610; 28-105/3.5-4.5, 75-300/4.5-5.6 AF, 50/1.8D Nikkors; MF Nikkors: 50/2K, 50/1.4 AI-S, 50/1.8 SeriesE, 60/2.8 Micro Nikkor (AF locked), 85mm/1.8K-AI, 105/2.5 AIS/P.C, 135/2.8K/Q.C, 180/2.8 ED, 200/4Q/AIS, 300/4.5H-AI, ++ Tamron 70-210/3.8-4, Vivitar/Kiron 28/2, ser.1 70-210/3.5, ser.1 28-90; Vivitar/Komine 28/2.8; 35mm Nikon F/FM/FE2, Rebel 2K

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egordon99
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May 07, 2010 13:20 |  #4

phil_5 wrote in post #10139610external link
Thank You Kitacanon. That's more along the lines of the intelligent answer I was looking for.

You asked us if the lenses you owned were parfocal vs. varifocal. I didn't know which lenses you owned. How is that not intelligent? :confused:




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wimg
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May 07, 2010 16:44 |  #5

A parfocal lens is a zoom lens that stays in focus at the same point where you set it regardless of the focal length you zoom to. Ideally you focus at the longest FL (for best accuracy) and then zoom to the desired FL. AFAIK, all current Canon zoom lenses are not parfocal. To a large degree this has to do with the fact that AF zoomlenses have relatively few and realtively loose focusing cams in order to make autofocusing possible with relativly weak focusing motors. Also, parfocal lenses are more difficult and more expensive to implement.

A varifocal lens is a zoom lens. Just a different name, used in the days when zoom lenses were new, and normally signifying a zoom lens with a very short zoom range, more useful for framing than actually zooming. The Tokina 11-16 could be considered a varifocal lens. Till this day I still use shorter zoom lenses as varifocal lenses, IOW, a prime with a framing option.

Kind regards, Wim


5D Mk II with a gaggle of primes & a solitary zoom, OM-D E-M5 Mk II with 5 primes and 5 zooms, G10, an accessory plague, and some analog stuff

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kitacanon
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May 08, 2010 08:13 |  #6

Good call Wim...
We might add as well that "vari" can also refer to variable aperture, in which the widest aperture varies from widest FL to the longest FL...e.g. 28-105mm 3.5-4.5 which would be F3.5 @ 28mm and 4.5 @ 105mm and varies in between, e.g. F4 @ 70mm
....not a serious problem until you go from 3.5 to 5.6 where the smallest wide aperture may be too small to use shutter speeds fast enough to stop action indoors...that lens may have image stabilization (IS) to stop YOUR action (shakes/jitters) but IS doesn't stop action in FRONT of you.

There, now I think we've covered it...


My Canon kit 30D/450D/s90; Canon lenses 50/1.8MKI, 18-55 IS, 35/2, 28-105/3.5-4.5, and 70-210/3.5-4.5....The Nikon kit: D610; 28-105/3.5-4.5, 75-300/4.5-5.6 AF, 50/1.8D Nikkors; MF Nikkors: 50/2K, 50/1.4 AI-S, 50/1.8 SeriesE, 60/2.8 Micro Nikkor (AF locked), 85mm/1.8K-AI, 105/2.5 AIS/P.C, 135/2.8K/Q.C, 180/2.8 ED, 200/4Q/AIS, 300/4.5H-AI, ++ Tamron 70-210/3.8-4, Vivitar/Kiron 28/2, ser.1 70-210/3.5, ser.1 28-90; Vivitar/Komine 28/2.8; 35mm Nikon F/FM/FE2, Rebel 2K

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rvdw98
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May 08, 2010 08:57 |  #7

egordon99 wrote in post #10139648external link
You asked us if the lenses you owned were parfocal vs. varifocal. I didn't know which lenses you owned. How is that not intelligent? :confused:

Actually, he asked how to tell them apart. To explain that, you don't need to know which lenses he owns. ;)


Roy

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wimg
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May 08, 2010 15:11 |  #8

kitacanon wrote in post #10143533external link
Good call Wim...
We might add as well that "vari" can also refer to variable aperture, in which the widest aperture varies from widest FL to the longest FL...e.g. 28-105mm 3.5-4.5 which would be F3.5 @ 28mm and 4.5 @ 105mm and varies in between, e.g. F4 @ 70mm
....not a serious problem until you go from 3.5 to 5.6 where the smallest wide aperture may be too small to use shutter speeds fast enough to stop action indoors...that lens may have image stabilization (IS) to stop YOUR action (shakes/jitters) but IS doesn't stop action in FRONT of you.

There, now I think we've covered it...

Thank you.

However, I hope you don't mind, but I don't agree with varifocal referring to variable aperture width or size when zooming. In the term varifocal two words are put together which say something about variation of something and about focal length. And that is all it really means, AFAIAC :D, variation of FL, or varying FL, unless the definition has changed dramatically since the early seventies and after the early nineties of last century :D.

Kindest regards, Wim ;)


5D Mk II with a gaggle of primes & a solitary zoom, OM-D E-M5 Mk II with 5 primes and 5 zooms, G10, an accessory plague, and some analog stuff

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kitacanon
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May 09, 2010 09:52 |  #9

No problem Wim...I was just thinking that while we were explaining the technologies of zoom lenses I might as well finish it off by explaining variable-apertures...just in case OP might not know that either...


My Canon kit 30D/450D/s90; Canon lenses 50/1.8MKI, 18-55 IS, 35/2, 28-105/3.5-4.5, and 70-210/3.5-4.5....The Nikon kit: D610; 28-105/3.5-4.5, 75-300/4.5-5.6 AF, 50/1.8D Nikkors; MF Nikkors: 50/2K, 50/1.4 AI-S, 50/1.8 SeriesE, 60/2.8 Micro Nikkor (AF locked), 85mm/1.8K-AI, 105/2.5 AIS/P.C, 135/2.8K/Q.C, 180/2.8 ED, 200/4Q/AIS, 300/4.5H-AI, ++ Tamron 70-210/3.8-4, Vivitar/Kiron 28/2, ser.1 70-210/3.5, ser.1 28-90; Vivitar/Komine 28/2.8; 35mm Nikon F/FM/FE2, Rebel 2K

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wimg
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May 09, 2010 10:30 |  #10

kitacanon wrote in post #10148587external link
No problem Wim...I was just thinking that while we were explaining the technologies of zoom lenses I might as well finish it off by explaining variable-apertures...just in case OP might not know that either...

Ok, thanks. It looks like I misunderstood your message in that case. Apologies for that.

Kind regards, Wim


5D Mk II with a gaggle of primes & a solitary zoom, OM-D E-M5 Mk II with 5 primes and 5 zooms, G10, an accessory plague, and some analog stuff

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Difference between parfocal and varifocal
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