SMC Pentax-A Zoom 35-105mm Varifocal or Parafocal?

writeb · 04-22-2010, 06:04 PM

Do any of you guys know if the Pentax-A Zoom 1:3.5 35~105mm lens is a Varifocal (Loses focus after zooming/panning) or a Parafocal (keeps focus despite zooming) type of lens?

You'll help out a lot. Thanks!

WriteB

Ratmagiclady · 04-22-2010, 06:12 PM

I can't say for sure, but if you're asking that question, you probably want that lens.

I have the Canon FD equivalent, all report says it's an Angenieux design. The Pentax has the same rep.

I do not call mine a zoom lens: I name, 'Small Stack Of Primes.'

JeffJS · 04-22-2010, 06:12 PM

I've read that they can vary. Mine stays in focus across the zoom range however.

Adam · 04-22-2010, 06:14 PM

I believe it is varifocal, but I haven't used it in a while, so don't quite me on that. I regardless hold that it's the best MF walkaround zoom, though!

Adam
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Ratmagiclady · 04-22-2010, 06:18 PM

I'd also add that if it's as similar a design as it appears, any variation in focus is no more than any last-moment correction in practice.

writeb · 04-22-2010, 06:50 PM

Agreed that it's a great lens. The issue is I sold it but the buyer (IMHO foolishly) Implied the lens is defective because it doesn't retain focus when you zoom/pan. I thought that was expected behavior. To my knowledge, these type of lenses - particularly macros, were varifocals, but I'd love to know for sure either way.

Thanks again for all the quick responses.

SOldBear · 04-22-2010, 07:31 PM

From what I remember (sold mine more than 2 yrs ago), the focus does change when you zoom, not as much as, say, the Vivitar Series 1 28-105mm, but it does change nonetheless.

Adam · 04-22-2010, 10:30 PM

Yup- now I remember clearly. It is most definitely varifocal as 1. it doesn't have a combined focus/zoom ring, and 2. it has a macro mode, and its focal point must change with zoom (if it didn't we'd have one killer of a macro lens!).

taurus9 · 04-22-2010, 11:12 PM

I have one and definitely varifocal.
In some cases, you may be able to get away without refocusing after zooming, but generally speaking you should refocus.

hangu · 04-22-2010, 11:31 PM

It is indeed varifocal. I sometimes use the zoom ring to focus (I'm sick in the head).

You sold it? Congratulations, you've just sold your soul. This is literally the only zoom lens I'll use.

writeb · 04-23-2010, 12:00 AM

LOL, put away the pitchforks

The buyer sent it back to me, and I'm seriously considering keeping it, especially after the bunch of test photos I took with it this evening. I was hell bent on getting a macro lens, which was my original purpose for buying it. As you know, the macro capability is.... adequate, but left a bit to be desired in that respect. I picked up an awesome D-FA 100mm Macro, and felt I was sane and cured of my LBA and tried to sell the 35-105.

Looking at the lens again from a walk around zoom perspective, has opened my eyes.

Now to deal with this negative ebay feedback

madhurvyas · 04-23-2010, 12:08 AM

I think this lens is parafocal but with one issue, the barrel extends little bit when we zoom the lens, if using small aperture (larger DOF) it should be good enough parafocal.

hangu · 04-23-2010, 12:29 AM

I recently sent in my only macro lens in for repair so the 35-105 was my only macro capable lens for my trip to the botanical garden. It was more than adequate and the colors were brilliant. No other lens of mine render red and blue the same way.

ddhytz · 04-23-2010, 04:44 AM

It is varifocal for sure. Especially when it is used on a manual focusing film body you need to zoom in first for focusing, then zoom out for composition.

On digital bodies it seems you don't need to do so. I guess that is due to different focusing system, optical vs electonical.

hangu · 04-23-2010, 07:42 AM

Originally posted by ddhytz

It is varifocal for sure. Especially when it is used on a manual focusing film body you need to zoom in first for focusing, then zoom out for composition.

On digital bodies it seems you don't need to do so. I guess that is due to different focusing system, optical vs electonical.

Those first two sentences made no sense at all, what exactly are you trying to say?

I'm going to have to disagree with you completely on every point. There is no difference in focusing systems between digital and SLR bodies, since the lens itself is doing all the focusing.

-------------

OP how much did you sell your 35-105 for? Link to the auction?

04-22-2010, 06:04 PM	#1
writeb Senior Member Join Date: Nov 2009 Location: San Jose Photos: Gallery \| Albums Posts: 150	SMC Pentax-A Zoom 35-105mm Varifocal or Parafocal? Do any of you guys know if the Pentax-A Zoom 1:3.5 35~105mm lens is a Varifocal (Loses focus after zooming/panning) or a Parafocal (keeps focus despite zooming) type of lens? You'll help out a lot. Thanks! WriteB

04-22-2010, 10:30 PM	#8
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,594	Yup- now I remember clearly. It is most definitely varifocal as 1. it doesn't have a combined focus/zoom ring, and 2. it has a macro mode, and its focal point must change with zoom (if it didn't we'd have one killer of a macro lens!). Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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04-22-2010, 06:12 PM	#2
Ratmagiclady Veteran Member Join Date: Nov 2008 Location: GA Photos: Gallery \| Albums Posts: 13,563	I can't say for sure, but if you're asking that question, you probably want that lens. I have the Canon FD equivalent, all report says it's an Angenieux design. The Pentax has the same rep. I do not call mine a zoom lens: I name, 'Small Stack Of Primes.'

04-22-2010, 06:12 PM	#3
JeffJS Inactive Account Join Date: Aug 2008 Location: Michigan, USA Photos: Gallery \| Albums Posts: 7,484	I've read that they can vary. Mine stays in focus across the zoom range however.

04-22-2010, 06:14 PM	#4
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,594	I believe it is varifocal, but I haven't used it in a while, so don't quite me on that. I regardless hold that it's the best MF walkaround zoom, though! Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

04-22-2010, 06:18 PM	#5
Ratmagiclady Veteran Member Join Date: Nov 2008 Location: GA Photos: Gallery \| Albums Posts: 13,563	I'd also add that if it's as similar a design as it appears, any variation in focus is no more than any last-moment correction in practice.

04-22-2010, 06:50 PM	#6
writeb Senior Member Join Date: Nov 2009 Location: San Jose Photos: Gallery \| Albums Posts: 150 Original Poster	Agreed that it's a great lens. The issue is I sold it but the buyer (IMHO foolishly) Implied the lens is defective because it doesn't retain focus when you zoom/pan. I thought that was expected behavior. To my knowledge, these type of lenses - particularly macros, were varifocals, but I'd love to know for sure either way. Thanks again for all the quick responses.

04-22-2010, 07:31 PM	#7
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	From what I remember (sold mine more than 2 yrs ago), the focus does change when you zoom, not as much as, say, the Vivitar Series 1 28-105mm, but it does change nonetheless.

04-22-2010, 11:12 PM	#9
taurus9 Senior Member Join Date: Jan 2010 Location: British Columbia Posts: 120	I have one and definitely varifocal. In some cases, you may be able to get away without refocusing after zooming, but generally speaking you should refocus.

04-22-2010, 11:31 PM	#10
hangu Veteran Member Join Date: Feb 2010 Location: NYC Photos: Gallery Posts: 1,071	It is indeed varifocal. I sometimes use the zoom ring to focus (I'm sick in the head). You sold it? Congratulations, you've just sold your soul. This is literally the only zoom lens I'll use.

04-23-2010, 12:00 AM	#11
writeb Senior Member Join Date: Nov 2009 Location: San Jose Photos: Gallery \| Albums Posts: 150 Original Poster	LOL, put away the pitchforks The buyer sent it back to me, and I'm seriously considering keeping it, especially after the bunch of test photos I took with it this evening. I was hell bent on getting a macro lens, which was my original purpose for buying it. As you know, the macro capability is.... adequate, but left a bit to be desired in that respect. I picked up an awesome D-FA 100mm Macro, and felt I was sane and cured of my LBA and tried to sell the 35-105. Looking at the lens again from a walk around zoom perspective, has opened my eyes. Now to deal with this negative ebay feedback

04-23-2010, 12:08 AM	#12
madhurvyas Veteran Member Join Date: Jan 2008 Location: Bikaner (Raj)-India Photos: Gallery Posts: 562	I think this lens is parafocal but with one issue, the barrel extends little bit when we zoom the lens, if using small aperture (larger DOF) it should be good enough parafocal.

04-23-2010, 12:29 AM	#13
hangu Veteran Member Join Date: Feb 2010 Location: NYC Photos: Gallery Posts: 1,071	I recently sent in my only macro lens in for repair so the 35-105 was my only macro capable lens for my trip to the botanical garden. It was more than adequate and the colors were brilliant. No other lens of mine render red and blue the same way.

04-23-2010, 04:44 AM	#14
ddhytz Veteran Member Join Date: Sep 2007 Location: Melbourne Posts: 602	It is varifocal for sure. Especially when it is used on a manual focusing film body you need to zoom in first for focusing, then zoom out for composition. On digital bodies it seems you don't need to do so. I guess that is due to different focusing system, optical vs electonical.

04-23-2010, 07:42 AM	#15
hangu Veteran Member Join Date: Feb 2010 Location: NYC Photos: Gallery Posts: 1,071	Originally posted by ddhytz It is varifocal for sure. Especially when it is used on a manual focusing film body you need to zoom in first for focusing, then zoom out for composition. On digital bodies it seems you don't need to do so. I guess that is due to different focusing system, optical vs electonical. Those first two sentences made no sense at all, what exactly are you trying to say? I'm going to have to disagree with you completely on every point. There is no difference in focusing systems between digital and SLR bodies, since the lens itself is doing all the focusing. ------------- OP how much did you sell your 35-105 for? Link to the auction?