18-55 WR Lens Design Issue

aaronkeogh · 03-30-2012, 02:27 PM

I really love the using the K-5 with the 18-55 kit lens, but the 18-55 lens has one design flaw in my opinion that is really annoying!! I like to shoot at 18mm/ 27mm (35mm Equivalent) most of the time but what I've noticed is that the lens easily changes focal length with any minor pressure to the front element. When you zoom from 18mm to 55mm the front element goes out at 18mm - in at 35mm and out at 55mm. Wouldn't it have been better if they designed it so that 18mm was as far back as it could be and 55mm was as far out as it could be rather than oscillating out, in and out? Maybe this is common with all 18-55 lenses, even from Nikon and Canon etc...

**RKKS08** · 03-30-2012, 02:40 PM

I think they searched for a design which promised the best IQ at a given maximum price. This was the result. Obviously designs offering other advantages were ruled out if considered to negatively effect IQ, cost (and probably also size/weight)

EDIT: Sorry, my post was only related to the out/in/out subject. About the ineffective damping: I had the first version of this lens, and now the WR one, and with both never felt this was a problem. I don't like the poor damping of the focus in manual, but this is a problem with nearly all AF lenses.

JinDesu · 03-30-2012, 02:40 PM

I dunno about other 18-55 lenses, but the non-WR version is very light on the zoom resistance too. And the zoom action goes out-in-out, which isn't such a bad design since it reduces the extension the lens has under full zoom (my Sigma 17-70 is unusable at close quarters and fully zoomed in).

But the light zoom dampening made me feel the lens was cheap, and I'm very picky. So I sorta agree with you on that part. I wish the zoom was more well dampened.

**dms** · 03-30-2012, 04:31 PM

I don't have that lens, but would a piece of photo tape (black gaffer's tape that leaves no residue) work? I use it to set/hold lenses at particular aperture and focus distance.

Docrwm · 03-30-2012, 05:10 PM

The dampening on my two 18-55s is just fine IMHO. The 18-55s have more resistance to being pushed in than any of my F series zooms. The lens from Pentax that is the easiest to push in, that I own, is the 18-135 - which is far easier than the 18-55s.

Giklab · 03-30-2012, 11:43 PM

Every kit lens (18-55) zooms like that. 100% certain for C, N and Pentax.

sterretje · 03-31-2012, 03:58 AM

Originally posted by aaronkeogh

... what I've noticed is that the lens easily changes focal length with any minor pressure to the front element

I'm probably missing something but when do you apply pressure to the front element?

Ben_Edict · 03-31-2012, 08:11 AM

Originally posted by aaronkeogh

I really love the using the K-5 with the 18-55 kit lens, but the 18-55 lens has one design flaw in my opinion that is really annoying!! I like to shoot at 18mm/ 27mm (35mm Equivalent) most of the time but what I've noticed is that the lens easily changes focal length with any minor pressure to the front element. When you zoom from 18mm to 55mm the front element goes out at 18mm - in at 35mm and out at 55mm. Wouldn't it have been better if they designed it so that 18mm was as far back as it could be and 55mm was as far out as it could be rather than oscillating out, in and out? Maybe this is common with all 18-55 lenses, even from Nikon and Canon etc...

There is s simple reason for having the front element in its forward position at the shortest focal length: the lens hood won't vignette then, wheras you might get dark corners, if the front lens would be inwards at 18mm. I never tried, how close the standard hood is in its form, but at least from the point of basic logic, this makes sense.
By the way, many shorter fl zoom lenses behave the same way, for instance the really good and big FA 28-70/2.8.

Ben

JinDesu · 03-31-2012, 08:14 AM

Originally posted by Docrwm

The dampening on my two 18-55s is just fine IMHO. The 18-55s have more resistance to being pushed in than any of my F series zooms. The lens from Pentax that is the easiest to push in, that I own, is the 18-135 - which is far easier than the 18-55s.

I didn't know that: I've only owned the 18-55, 80-200, and 100-300, and I think I agree, they were all easy to zoom. I guess after using Sigma lenses, I really like a well damped zoom (personal preference).

Asha · 04-08-2012, 08:39 PM

Originally posted by aaronkeogh

I really love the using the K-5 with the 18-55 kit lens, but the 18-55 lens has one design flaw in my opinion that is really annoying!! I like to shoot at 18mm/ 27mm (35mm Equivalent) most of the time but what I've noticed is that the lens easily changes focal length with any minor pressure to the front element. When you zoom from 18mm to 55mm the front element goes out at 18mm - in at 35mm and out at 55mm. Wouldn't it have been better if they designed it so that 18mm was as far back as it could be and 55mm was as far out as it could be rather than oscillating out, in and out? Maybe this is common with all 18-55 lenses, even from Nikon and Canon etc...

The out-in-out is typical of zoom lenses--it is by design for many available lenses, not just Pentax. A zoom lens is very convenient, but since you can't easily remove and replace optical elements inside the lens, the only thing the design can really do is change the individual elements' airspace thicknesses and the relative aperture stop location. Incidentally, this is also why the F/# may change over the zoom range.

aaronkeogh · 04-10-2012, 04:27 PM

Yes a zoom is convenient but for the K-5's crop sensor their isn't really a great choice of wide angle lenses in the range of 28-35mm (35mm Equivalent). Yes their is the 21mm prime, and the 18-55mm zoom but the other wide angle lenses offer a lot more distortion and are more like fisheyes than good wide angle lenses. Pentax only seem to bring out tele lenses, maybe a full frame camera would solve this and open up some of the older wide angle Pentax lenses as an option.

sterretje · 04-11-2012, 02:56 AM

Originally posted by aaronkeogh

Yes their is the 21mm prime, and the 18-55mm zoom but the other wide angle lenses offer a lot more distortion and are more like fisheyes than good wide angle lenses.

If I must believe photozone.de (and I do believe them on this), a DA15Ltd has a lot less barrel distortion at 15mm than the kit lens at 18mm. OK, equivalent of 24mm and not 28mm what you prefer.

Marc Sabatella · 04-11-2012, 01:33 PM

There is also the 14, 17-70, the 16-45, and the 12-24, any of which should have less distortion than either the 18-55 or 21. then there is also the 18-135, and of course any number of other options from Tamron and Sigma. Not sure why you'd say there aren't enough choices here. How many choice do you need?

03-30-2012, 02:27 PM	#1
aaronkeogh New Member Join Date: Feb 2012 Posts: 7	18-55 WR Lens Design Issue I really love the using the K-5 with the 18-55 kit lens, but the 18-55 lens has one design flaw in my opinion that is really annoying!! I like to shoot at 18mm/ 27mm (35mm Equivalent) most of the time but what I've noticed is that the lens easily changes focal length with any minor pressure to the front element. When you zoom from 18mm to 55mm the front element goes out at 18mm - in at 35mm and out at 55mm. Wouldn't it have been better if they designed it so that 18mm was as far back as it could be and 55mm was as far out as it could be rather than oscillating out, in and out? Maybe this is common with all 18-55 lenses, even from Nikon and Canon etc...

03-30-2012, 02:40 PM	#2
RKKS08 Site Supporter Join Date: Mar 2010 Location: Frankfurt am Main Posts: 1,241	I think they searched for a design which promised the best IQ at a given maximum price. This was the result. Obviously designs offering other advantages were ruled out if considered to negatively effect IQ, cost (and probably also size/weight) EDIT: Sorry, my post was only related to the out/in/out subject. About the ineffective damping: I had the first version of this lens, and now the WR one, and with both never felt this was a problem. I don't like the poor damping of the focus in manual, but this is a problem with nearly all AF lenses. Last edited by RKKS08; 03-30-2012 at 02:49 PM.

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03-30-2012, 02:40 PM	#3
JinDesu Veteran Member Join Date: Jun 2011 Location: New York City Photos: Gallery Posts: 5,638	I dunno about other 18-55 lenses, but the non-WR version is very light on the zoom resistance too. And the zoom action goes out-in-out, which isn't such a bad design since it reduces the extension the lens has under full zoom (my Sigma 17-70 is unusable at close quarters and fully zoomed in). But the light zoom dampening made me feel the lens was cheap, and I'm very picky. So I sorta agree with you on that part. I wish the zoom was more well dampened.

03-30-2012, 04:31 PM	#4
dms Site Supporter Join Date: Aug 2011 Location: New York, NY Photos: Gallery Posts: 2,192	I don't have that lens, but would a piece of photo tape (black gaffer's tape that leaves no residue) work? I use it to set/hold lenses at particular aperture and focus distance.

03-30-2012, 05:10 PM	#5
Docrwm Veteran Member Join Date: Sep 2010 Location: Somewhere in the Southern US Photos: Gallery \| Albums Posts: 12,285	The dampening on my two 18-55s is just fine IMHO. The 18-55s have more resistance to being pushed in than any of my F series zooms. The lens from Pentax that is the easiest to push in, that I own, is the 18-135 - which is far easier than the 18-55s.

03-30-2012, 11:43 PM	#6
Giklab Veteran Member Join Date: Jan 2012 Location: Slovenia Photos: Gallery Posts: 2,182	Every kit lens (18-55) zooms like that. 100% certain for C, N and Pentax.

03-31-2012, 03:58 AM	#7
sterretje Veteran Member Join Date: Dec 2008 Location: Roodepoort, South Africa Photos: Gallery \| Albums Posts: 3,561	Originally posted by aaronkeogh ... what I've noticed is that the lens easily changes focal length with any minor pressure to the front element I'm probably missing something but when do you apply pressure to the front element?

03-31-2012, 08:11 AM	#8
Ben_Edict Veteran Member Join Date: Jul 2007 Location: SouthWest "Regio" Photos: Albums Posts: 3,309	Originally posted by aaronkeogh I really love the using the K-5 with the 18-55 kit lens, but the 18-55 lens has one design flaw in my opinion that is really annoying!! I like to shoot at 18mm/ 27mm (35mm Equivalent) most of the time but what I've noticed is that the lens easily changes focal length with any minor pressure to the front element. When you zoom from 18mm to 55mm the front element goes out at 18mm - in at 35mm and out at 55mm. Wouldn't it have been better if they designed it so that 18mm was as far back as it could be and 55mm was as far out as it could be rather than oscillating out, in and out? Maybe this is common with all 18-55 lenses, even from Nikon and Canon etc... There is s simple reason for having the front element in its forward position at the shortest focal length: the lens hood won't vignette then, wheras you might get dark corners, if the front lens would be inwards at 18mm. I never tried, how close the standard hood is in its form, but at least from the point of basic logic, this makes sense. By the way, many shorter fl zoom lenses behave the same way, for instance the really good and big FA 28-70/2.8. Ben

03-31-2012, 08:14 AM	#9
JinDesu Veteran Member Join Date: Jun 2011 Location: New York City Photos: Gallery Posts: 5,638	Originally posted by Docrwm The dampening on my two 18-55s is just fine IMHO. The 18-55s have more resistance to being pushed in than any of my F series zooms. The lens from Pentax that is the easiest to push in, that I own, is the 18-135 - which is far easier than the 18-55s. I didn't know that: I've only owned the 18-55, 80-200, and 100-300, and I think I agree, they were all easy to zoom. I guess after using Sigma lenses, I really like a well damped zoom (personal preference).

04-08-2012, 08:39 PM	#10
Asha Senior Member Join Date: Mar 2012 Photos: Albums Posts: 100	Originally posted by aaronkeogh I really love the using the K-5 with the 18-55 kit lens, but the 18-55 lens has one design flaw in my opinion that is really annoying!! I like to shoot at 18mm/ 27mm (35mm Equivalent) most of the time but what I've noticed is that the lens easily changes focal length with any minor pressure to the front element. When you zoom from 18mm to 55mm the front element goes out at 18mm - in at 35mm and out at 55mm. Wouldn't it have been better if they designed it so that 18mm was as far back as it could be and 55mm was as far out as it could be rather than oscillating out, in and out? Maybe this is common with all 18-55 lenses, even from Nikon and Canon etc... The out-in-out is typical of zoom lenses--it is by design for many available lenses, not just Pentax. A zoom lens is very convenient, but since you can't easily remove and replace optical elements inside the lens, the only thing the design can really do is change the individual elements' airspace thicknesses and the relative aperture stop location. Incidentally, this is also why the F/# may change over the zoom range.

04-10-2012, 04:27 PM	#11
aaronkeogh New Member Join Date: Feb 2012 Posts: 7 Original Poster	Yes a zoom is convenient but for the K-5's crop sensor their isn't really a great choice of wide angle lenses in the range of 28-35mm (35mm Equivalent). Yes their is the 21mm prime, and the 18-55mm zoom but the other wide angle lenses offer a lot more distortion and are more like fisheyes than good wide angle lenses. Pentax only seem to bring out tele lenses, maybe a full frame camera would solve this and open up some of the older wide angle Pentax lenses as an option.

04-11-2012, 02:56 AM	#12
sterretje Veteran Member Join Date: Dec 2008 Location: Roodepoort, South Africa Photos: Gallery \| Albums Posts: 3,561	Originally posted by aaronkeogh Yes their is the 21mm prime, and the 18-55mm zoom but the other wide angle lenses offer a lot more distortion and are more like fisheyes than good wide angle lenses. If I must believe photozone.de (and I do believe them on this), a DA15Ltd has a lot less barrel distortion at 15mm than the kit lens at 18mm. OK, equivalent of 24mm and not 28mm what you prefer.

04-11-2012, 01:33 PM	#13
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	There is also the 14, 17-70, the 16-45, and the 12-24, any of which should have less distortion than either the 18-55 or 21. then there is also the 18-135, and of course any number of other options from Tamron and Sigma. Not sure why you'd say there aren't enough choices here. How many choice do you need?