What do they mean by variable focusing on this Vivitar 28-85, please?

bladerunner6 · 06-17-2015, 05:46 PM

My widest fast lens is my plastic fantastic 35, so I was thinking about this since a local thrift store has it for $25.

Vivitar 28-85mm f2.8-3.8 Variable Focusing Lens Reviews - Vivitar Lenses - Pentax Lens Review Database

What does "variable focusing" mean, please?

Thanks.

aleonx3 · 06-17-2015, 05:50 PM

I am not too sure, but I think it could mean the opposite of para-focal (once focus is attained, the focus remain unchanged while changing focal length of the lens).

vonBaloney · 06-17-2015, 06:07 PM

Originally posted by aleonx3

I am not too sure, but I think it could mean the opposite of para-focal (once focus is attained, the focus remain unchanged while changing focal length of the lens).

Yes, that's right. Variable focusing meant that you had to re-focus if you zoomed at all (unusual for the time, I guess), and by paying that price the lens could be designed so image quality would be greater (in theory, anyway).

Aaron28 · 06-17-2015, 07:42 PM

I have a vivitar 28-105 and must refocus when ever I change the zoom (focal length) unlike other zooms that maintain

bladerunner6 · 06-18-2015, 02:25 AM

Thanks, this is useful. For the price, I might try it.

TaoMaas · 06-18-2015, 04:53 AM

I'm not familiar with this lens, but I did used to have the Vivitar Series 1 28-90, which is kind of the "big brother" of this lens. It was a well-built, heavy lens that made great images on film. Or at least, it did up until I dropped it off my tripod.

aleonx3 · 06-18-2015, 05:49 AM

Originally posted by bladerunner6

Thanks, this is useful. For the price, I might try it.

The advantage of para-focal is that you can zoom in to focus (manually) and then zoom out to frame; with this lens, you don't enjoy that advantage. I just want to point out to you as you said you might try it.

06-17-2015, 05:46 PM	#1
bladerunner6 Pentaxian Join Date: Nov 2014 Photos: Albums Posts: 2,080	What do they mean by variable focusing on this Vivitar 28-85, please? My widest fast lens is my plastic fantastic 35, so I was thinking about this since a local thrift store has it for $25. Vivitar 28-85mm f2.8-3.8 Variable Focusing Lens Reviews - Vivitar Lenses - Pentax Lens Review Database What does "variable focusing" mean, please? Thanks.

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06-17-2015, 05:50 PM	#2
aleonx3 Veteran Member Join Date: Jul 2007 Location: Brampton, Ontario Photos: Gallery \| Albums Posts: 3,996	I am not too sure, but I think it could mean the opposite of para-focal (once focus is attained, the focus remain unchanged while changing focal length of the lens).

06-17-2015, 06:07 PM	#3
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	Originally posted by aleonx3 I am not too sure, but I think it could mean the opposite of para-focal (once focus is attained, the focus remain unchanged while changing focal length of the lens). Yes, that's right. Variable focusing meant that you had to re-focus if you zoomed at all (unusual for the time, I guess), and by paying that price the lens could be designed so image quality would be greater (in theory, anyway).

06-17-2015, 07:42 PM	#4
Aaron28 Pentaxian Join Date: Jan 2015 Location: Huntsville, Al Posts: 7,131	I have a vivitar 28-105 and must refocus when ever I change the zoom (focal length) unlike other zooms that maintain

06-18-2015, 02:25 AM	#5
bladerunner6 Pentaxian Join Date: Nov 2014 Photos: Albums Posts: 2,080 Original Poster	Thanks, this is useful. For the price, I might try it.

06-18-2015, 04:53 AM	#6
TaoMaas Pentaxian Join Date: May 2007 Location: Oklahoma City Photos: Gallery \| Albums Posts: 3,574	I'm not familiar with this lens, but I did used to have the Vivitar Series 1 28-90, which is kind of the "big brother" of this lens. It was a well-built, heavy lens that made great images on film. Or at least, it did up until I dropped it off my tripod.

06-18-2015, 05:49 AM	#7
aleonx3 Veteran Member Join Date: Jul 2007 Location: Brampton, Ontario Photos: Gallery \| Albums Posts: 3,996	Originally posted by bladerunner6 Thanks, this is useful. For the price, I might try it. The advantage of para-focal is that you can zoom in to focus (manually) and then zoom out to frame; with this lens, you don't enjoy that advantage. I just want to point out to you as you said you might try it.