Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-24-2010, 06:29 PM   #1
Veteran Member
creampuff's Avatar

Join Date: May 2007
Location: Singapore
Photos: Gallery
Posts: 3,955
Can the plastic lens mount on cheap Pentax lenses be replaced?

As we all know Pentax has done away with using a metal lens mount and using polycarbonate plastic for a number of el-cheapo consumer grade lenses as a means of saving money. Some of the cheap FA, FAJ and now DAL zoom lenses all use plastic lens mounts.

Just wondering if anybody has substituted the plastic mount with a metal one cannibalized from a dead lens? Is it even possible to retro-fit given that the pins don't look the same? I've got one el-cheapo Pentax zoom but after seeing plenty of Canon and Nikon kit lenses with broken or sheared off plastic lens mounts, I'm toying with the idea to replace the plastic mount with a metal one on my lens to make it more durable.

Good idea or not? Any thoughts?

06-24-2010, 06:55 PM   #2
Moderator
Site Supporter
Blue's Avatar

Join Date: Jun 2008
Location: Florida Hill Country
Photos: Gallery | Albums
Posts: 17,166
This thread is ironic given that there have been several threads the past month wanting more cheap plasti-mount 50 and 35mm lenses from Pentax.

I think there is a good chance it would work if you had a suitable donor mount.
06-24-2010, 07:33 PM   #3
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
I don;t think it is worth persuing.

although you might find a donor mount, the lens body is also plastic (at least on my FA-J 18-35)

This lens is now 8 years old and has never given me any trouble, so what is the big deal.

Much of my PZ-1 is polycarbonate and 20 years old with no issue.

Lets be realistic here, the plastics are pretty good in most cases.
06-24-2010, 11:29 PM   #4
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
I'd say, wait for the plastic to fail, and if that ever happens, then worry about replacing it.

06-25-2010, 12:03 AM   #5
Senior Member
allill's Avatar

Join Date: Aug 2008
Location: San Francisco, California
Posts: 267
I have a busted FA J 75-300mm, if I can find a donor, I will try to replace the mount.
06-25-2010, 02:10 AM   #6
Veteran Member
kevinschoenmakers's Avatar

Join Date: Mar 2009
Location: Shanghai
Photos: Gallery
Posts: 1,513
QuoteOriginally posted by Blue Quote
This thread is ironic given that there have been several threads the past month wanting more cheap plasti-mount 50 and 35mm lenses from Pentax.
That's not entirely true. The agruement went that it would be good for Pentax to have one or two dirt-cheap primes. And If that means a plastic mount, then so be it.
06-25-2010, 05:34 AM   #7
Pentaxian
bdery's Avatar

Join Date: Mar 2008
Location: Quebec city, Canada
Photos: Gallery
Posts: 5,650
There is no reason to replace the plastic mount with metal. Humans have a tendency to believe that metal is always stronger and more durable, but that's not based on anything serious. Plastic can be just as durable as metal, sometimes more durable. I have a 10 years old plastic mount lens sstill working. And I have a cheapcheapcheap vivitar plastic camera that I got as a kid that wtill works flawlessly.

If your plastic mount ever fails (how would it do that, for the record? It's a flat surface surrounded by the lens barrel) then consider replacing the lens with another similar one, or a more expensive one.
06-25-2010, 08:21 AM   #8
Veteran Member
creampuff's Avatar

Join Date: May 2007
Location: Singapore
Photos: Gallery
Posts: 3,955
Original Poster
Well I've owned plenty of cameras to know that polycarbonate plastic is pretty durable. However I recently went to a camera repair shop locally and the store owner showed me a drawer full of usable but damaged Nikon and Canon kit lenses. All had damage at the plastic bayonet mount either from being cracked or sheared off from impact. All junked because it costs more to repair or replace the damaged part than to buy new. So while plastic can do the job to lock the lens to the camera, for certain it isn't as durable compared to metal.

Now with regards to Pentax, I've owned the FA 100-300mm and now the FAJ 75-300mm zooms and both have plastic lens mounts. I have to say plastic just doesn't feel as secure as metal on metal and over time it looks scratched up. Also the lenses while light in weight, extend quite a bit and I worry that over time it will either somehow flex (which might conceivably affect element centering) or get damaged if I somehow knocked or bumped into something. So I thought it might be worth a go to replace it with a metal lens mount cannibalized from elsewhere.

06-25-2010, 08:51 AM   #9
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by creampuff Quote
Well I've owned plenty of cameras to know that polycarbonate plastic is pretty durable. However I recently went to a camera repair shop locally and the store owner showed me a drawer full of usable but damaged Nikon and Canon kit lenses. All had damage at the plastic bayonet mount either from being cracked or sheared off from impact.
I wonder, though, how a metal mount would have fared under the same circumstances. And I wonder if an impact strong enough to snap the mount might be just as likely to damage the lens in other ways - especially if the plastic mount hadn't absorbed so much of the shock while breaking. Also, if your equipment is insured (and it would cost literally pennies to insure a cheap plastic mount lens), I am not sure I'd be too worried.

Anyhow, not saying don't give it a shot if you're so inclined, nor am I saying I wouldn't prefer to buy lenses with metal mounts. Just trying to add a little perspective.
06-25-2010, 08:52 AM   #10
Pentaxian
Aegon's Avatar

Join Date: Jan 2008
Location: Portland, OR
Posts: 1,410
I wonder, if those lenses that failed from impact were made of metal instead of plastic, maybe instead of the lens breaking the camera mount would have broken.

Then the store would have a box of broken cameras instead a box of broken kit lenses.


¡Ay! Señor Sabatella beat me to the punch.
06-25-2010, 09:04 AM   #11
Moderator
Site Supporter
Blue's Avatar

Join Date: Jun 2008
Location: Florida Hill Country
Photos: Gallery | Albums
Posts: 17,166
QuoteOriginally posted by kevinschoenmakers Quote
That's not entirely true. The agruement went that it would be good for Pentax to have one or two dirt-cheap primes. And If that means a plastic mount, then so be it.
Yes, that is true. The removal of the metal mount from the FA 50 or 35 would save about $10 off the price. Plus, it is dumb to expect Pentax to spend money to R&D and lens that is going to net them $1 per lens if lucky given the other things they are hopefully working on. You guys keep pointing to the $99 Canon lens that has been around since 1990. Obviously Canon isn't putting R&D into a cheap lens to replace an existing lens either.
06-25-2010, 09:06 AM   #12
Moderator
Site Supporter
Blue's Avatar

Join Date: Jun 2008
Location: Florida Hill Country
Photos: Gallery | Albums
Posts: 17,166
QuoteOriginally posted by Aegon Quote
I wonder, if those lenses that failed from impact were made of metal instead of plastic, maybe instead of the lens breaking the camera mount would have broken.

Then the store would have a box of broken cameras instead a box of broken kit lenses.


¡Ay! Señor Sabatella beat me to the punch.
You and Marc are assuming the lenses were abused beyond normal use. Perhaps the things just gave up after a period of time like plastic in mechanical situations has a tendency to do. The mount is a mechanical interface. Most better bodies are a solid piece and have a metal chassis.
06-25-2010, 10:01 AM   #13
Pentaxian
Aegon's Avatar

Join Date: Jan 2008
Location: Portland, OR
Posts: 1,410
Yeah, I'm assuming abuse. That's why I wrote "those lenses that failed from impact". That's where I hid the assumption of abuse.

I've seen pictures of camera bodies where the mount was torn off from abuse. I just can't find it right now. I think the lens survived.

I also think that most plastic mount failures are caused by abuse rather than failure after normal use.
06-25-2010, 02:55 PM   #14
Veteran Member
creampuff's Avatar

Join Date: May 2007
Location: Singapore
Photos: Gallery
Posts: 3,955
Original Poster
Unlike cameras of the past which had a metal outer casing, the cameras nowadays use an internal metal skeleton that's covered by molded polycarbonate plastic shell. I faintly do recall seeing a K10D at my local Pentax service center awhile back which had it's lens mount sheared off. The screws holding the lens mount certainly didn't look like they were just screwed onto any metal frame. I figure it's robust enough for normal use but with a heavy lens mounted I don't think even a metal mount on today's cameras can withstand damage when subject to a severe shock like the camera being dropped.

Actually I'm a little disappointed that Pentax has opted for polycarbonate plastic for the lens mount on their DAL lenses. It certainly harkens back to the plethora of cheap consumer grade zoom lenses rolled out during the tenure of the previous Pentax management who came out with frankly forgettable plastic bodied film cameras that were commercial flops. Perhaps it's the dictates of the market because even however cheap the kit lens is, it is still a cost when bundled for sale with every camera body, so even a $10 saving is a lot when you're talking volume in the thousands.

I guess they feel price conscious rank newbies would either just be content to use the starter lenses blissfully ignorant of the quality difference of metal vs plastic, who also might not put these el-cheapo lenses to heavy usage and hence wear and tear (so plastic is good enough), or more likely encourage them to start buying other lenses in the lineup which have better build quality and image quality. I guess some clever Pentax executive must have reasoned that if the newbies have never used Quick Shift before, why include it. Same for putting distance markings on the DAL... it all adds up to extra cost.

After all, if people buy new lenses, that's money rolling in for Pentax, there's no money to be made if everyone stuck to kit lenses, so logically there's no compelling need to improve the build quality of the kit lenses.
I've seen the insides of the Nikon and Canon kit lenses and they are really crap. The lens elements are mostly plastic and even the aperture assembly on the Canon is a tiny little assembly. Everything is made not to last. I fear Pentax may edge closer to the slippery slope of following Canon and Nikon's lead with regards to cheapening the kit lenses.

Sorry guys but as much as plastic is good in saving weight and probably tough enuff for daily use, I'm sticking to metal. Had the el-cheapo plastic fantastic Cosina 100mm f/3.5 Macro (also comes in other guises like Phoenix, Vivitar, etc.) that was even rebadged as a Pentax. Well it's a pretty decent lens but it makes a good example of the pitfalls of going with plastic, wobbly lens barrel and all. I sold it because it always felt the lens was gonna fall apart in my hands. Looks like I'm gonna have to sell that FA J lens... FA J... J is for Junk)

Last edited by creampuff; 06-25-2010 at 03:11 PM.
06-25-2010, 05:27 PM   #15
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Blue Quote
You and Marc are assuming the lenses were abused beyond normal use.
Well, he may have assumed; I simply went along with what he explicitly wrote :-). But of course, you're right to imply that some lenses might fail in ordinary use. I'd just say that I know people who have plastic mount lenses who have never had problems, and I know none who have. While I agree plastic will have disadvantages (and most acutely with longer / heavier lenses that put more stress on the mount), I guess I just really don't hear many stories of them spontaneously breaking, so yes, I'm inclined to assume that's not what happened.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
el-cheapo, idea, k-mount, lens, lenses, metal, mounts, pentax, pentax lens, pentax lenses, plastic, plastic lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
All who would criticize cheap & plastic lenses - READ THIS! RioRico Pentax SLR Lens Discussion 43 04-15-2010 09:41 PM
For Sale - Sold: Promaster Lenses: 19-35mm (Plastic Fantastic) & 28-105mm (Tamron/Pentax clone) deadwolfbones Sold Items 23 08-20-2009 10:51 AM
old lenses- that little plastic white dot? dandaniel Pentax SLR Lens Discussion 6 02-25-2009 02:13 PM
Cheap manual lens on cheap extension tube with cheap flash! Also cats. pasipasi Post Your Photos! 12 08-28-2008 04:43 PM



All times are GMT -7. The time now is 08:07 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top