which nikon lens are parfocal?


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wind30

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Hi people,

I am wondering which nikon lens are parfocal, ie holds its focus while zooming? Is the new 18-200mm VR parfocal?

how about any third party lens?
 

Clown

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i tot all are? O_O"
dunno which lens changes its focal distance when u zoom...
 

wind30

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most don't. I am using an oly setup and my 14-54 and 20-200 is not parfocal. I have to refocus if I zoom in and out. Thinking to switching to a parfocal lens. so changing system
 

d7t3

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is that a good reason to change system?? you already have a good range of focal lengths covered. why not zoom before focusing?

anyway you should check first whether the lenses you want to buy are indeed parfocal.
 

Clown

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i dunno.. u mentioned nikon. so far most lenses i've worked with hasnt given me that problem.
 

lsisaxon

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wind30 said:
Hi people,

I am wondering which nikon lens are parfocal, ie holds its focus while zooming? Is the new 18-200mm VR parfocal?

how about any third party lens?
18-200VR is not parfocal. Neither is the 18-70/3.5-4.5 (D70 kit lens). The Sigma 18-125/3.5-5.6 does not seem to be parfocal either.

Most of the faster lenses are parfocal. Nikon 24-85/2.8-4, Nikon 80-200/2.8, Sigma EX 18-50/2.8. Nikon 17-35/2.8, Nikon 17-55/2.8 DX should be parfocal too but I don't have them.
I have not checked Nikon 12-24/4 and Sigma EX 12-24/4.5-5.6.
 

Clown

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lsisaxon said:
18-200VR is not parfocal. Neither is the 18-70/3.5-4.5 (D70 kit lens). The Sigma 18-125/3.5-5.6 does not seem to be parfocal either.

Most of the faster lenses are parfocal. Nikon 24-85/2.8-4, Nikon 80-200/2.8, Sigma EX 18-50/2.8. Nikon 17-35/2.8, Nikon 17-55/2.8 DX should be parfocal too but I don't have them.
I have not checked Nikon 12-24/4 and Sigma EX 12-24/4.5-5.6.
really? u sure? does it have markings stating that the focal point is different at different focal lengths? i dunno cuz i havent had the chance to play with one yet.

anyway.. some readup on parfocal nikkors: http://www.dsprelated.com/showmessage/28078/2.php
 

Ian

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Feb 20, 2002
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wind30 said:
Hi people,

I am wondering which nikon lens are parfocal, ie holds its focus while zooming? Is the new 18-200mm VR parfocal?

how about any third party lens?
Properly ANY lens that mounts on a Nikon SLR is Parfocal, as Parfocal means having the same focal plane to mounting distance, that is "coincident focal points".

What you should have asked for is "Parfocal Zoom Lens" or more accurately in optical terms a "constant focus zoom lens"

A zoom lens that changes focus while changing the focal length is knowns as a "Varifocal" lens.

The 17-35/2.8 AFS, 28-70/2.8 (D and AFS), 80-200/2.8 Two Touch lenses are all constant focus at around F8 though it seems to be a bit hit and miss at f2.8 which may be due to barrel slop. Not that it matters anyway as AF takes care of the issue these days.
 

Andy Ho

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I realised that if I zoom my 17-55mm lens to the tele end and focus before zooming back to wide angle the focus at wide angle is still good.

But if I focus at the wide end first before zooming in I see a slight off focus at the tele. It could be due to the camera's inadequacy to detect precise detail at the wide setting of my zoom and has nothing to do with the lens being or being not a parfocal zoom lens.

As for zooming out to focus before pulling back to wide with still good sharpness hints that the 17-55mm is indeed and most probably a parfocal zoom lens.

I am not so confident about the 24-85mm f/2.8-4 being a parfocal zoom though.
 

lsisaxon

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Andy Ho said:
I realised that if I zoom my 17-55mm lens to the tele end and focus before zooming back to wide angle the focus at wide angle is still good.

But if I focus at the wide end first before zooming in I see a slight off focus at the tele. It could be due to the camera's inadequacy to detect precise detail at the wide setting of my zoom and has nothing to do with the lens being or being not a parfocal zoom lens.

As for zooming out to focus before pulling back to wide with still good sharpness hints that the 17-55mm is indeed and most probably a parfocal zoom lens.

I am not so confident about the 24-85mm f/2.8-4 being a parfocal zoom though.
Yeah. It is always to use the long end to focus and the zoom out for a parfocal zoom. The 24-85/2.8-4 should be parfocal. It was one of my favourite lens after the 28-70/2.6. Haven't really scrutinize it on digital yet.
 

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