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03-15-2010, 04:56 PM   #1
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Does wet oilly blades affect M42 lens performance

I have this weird old brick Kenlock 80-200mm auto f/3.5 in M42 mount. The box of the lens actually mentions for Pentax. It is made in Japan, I think. Once I open up the rear and fix the Auto pin to stop down properly, the lens blades were found wet and oily. There is probably some oil leaking from the old m42 lens barrel and how it got lubricated in the old time. I fell short in knowing how to clean up the blades -- it will be too much time involved.


4. Kenlock 80-200mm f/3.5 Auto in M42 mount







Question: Am I right to assume and claim that oily blades don't affect M42 lens in performance? For one, the lens aperture is stopped down already as you change aperture. In other words, the diaphragm opening is stopped down. It is unlike the K-mount manual lens or AF lens that oily or sticky blades will affect the timing and shutter.

After I fix the aperture pin that the m42 acts as a fully manual diaphragm lens, it works reasonably well. The following are a few taken in f/8.0 and f/5.6 on K20D. The lens is reasonably sharp and bokeh is nice.












cropped







cropped



Shot wide open in f/3.5
soft bokeh



This old zoom is a two touch zoom and the zoom position is changed internally without altering the lens overall length. Even with a built-in lens hood, contrast sometimes is found to be a bit low but it is an easy fix in post processing. In f/4.0 to f/11.0, I mostly can use Av mode in K20D without going to M mode.

Anyone heard of this brand?

Thanks,
Hin


Last edited by hinman; 03-15-2010 at 05:12 PM.
03-15-2010, 05:16 PM   #2
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I seem to remember Kenlock equipment being sold in the UK many years ago, probably as a store brand.

It works though, and I think these old zooms are still useable as walkabout lenses. I've got a couple of old Vivitar one touch zooms that cost me next to nothing, they certainly don't have a great reputation ( compared to the Series One lenses for example ) but they do the job.

And if you know that the blades are oily and will possibly stick then you'll be ready to deal with that problem if it happens. It's a cheap lens, treat it like one.
03-15-2010, 06:01 PM   #3
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That lens looks suspiciously similar to the 2-touch Kiron zoom that Vivitar sold in a similar focal length.
03-15-2010, 06:22 PM   #4
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QuoteOriginally posted by hinman Quote
Question: Am I right to assume and claim that oily blades don't affect M42 lens in performance? For one, the lens aperture is stopped down already as you change aperture. In other words, the diaphragm opening is stopped down. It is unlike the K-mount manual lens or AF lens that oily or sticky blades will affect the timing and shutter.
I think you're right. If this were a valuable lens, clean blades would increase the resale value. It would make the repair worthwhile.

I did have one Sears lens where the internal elements on either side of the oily blades had a coat of oil on them. Cleaning that helped the lens a lot. It's unusual for the oil to be that bad.

I had a Soligor 80-200/3.5 C/D model that resembled this lens, except for the macro ring at the rear. It was heavy enough so I made sure to use the genuine M42 adapter. I compared it for sharpness with a Pentax-F 70-210mm f4-5.6 zoom for someone considering both lenses. The Pentax was sharper and way smaller, but they liked the Soligor enough to take it on a long trip anyway, despite its size and weight.

03-16-2010, 11:27 AM   #5
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Thanks for all the helpful replies. An extra question to follow

I wonder how difficult it is to clean the blades myself. I went so far in fixing the aperture pin to stop down properly. But I am afraid to go further down as I foresee difficulty in assembling the lens back.

In general, what are the methods and material used in cleaning aperture blades. How do you get it to dry? What sort of material to dry or re-lubricate the lens.

Thanks,
Hin
03-16-2010, 11:47 AM   #6
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QuoteOriginally posted by hinman Quote
I wonder how difficult it is to clean the blades myself. I went so far in fixing the aperture pin to stop down properly. But I am afraid to go further down as I foresee difficulty in assembling the lens back.

In general, what are the methods and material used in cleaning aperture blades. How do you get it to dry? What sort of material to dry or re-lubricate the lens.
Hey Hin,

Once you open the lens up, you might not stop tinkering. Better sell it on the Marketplace before you find yourself with another hobby...

Seriously, though, the oil can be cleaned off the aperture blades (once they are out of the lens) with lighter fluid, as in Zippo Lighters. You can either wipe them with a Q-tip soaked in the stuff (but be careful not to bend them or leave cotton strands), or just remove the blades completely and soak them in it.

There are tons of tutorials on the web outlining this for many different lenses. Your particular lens probably won't be explained, but find something similar and get to know the procedure. Then, as you take your lens apart, *take lots of pictures* so you have a visual reference of what it all looked like when it worked!

I'd bet you can get to the aperture assembly from the back, but you never can tell until you open it up. You'll have to remove some lens groups (which can be a tricky affair), but think twice if you find you have to remove the focusing helical or the zoom tubes. Some stuff is tricky to put back together...
03-16-2010, 05:55 PM   #7
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QuoteOriginally posted by panoguy Quote
Hey Hin,

Once you open the lens up, you might not stop tinkering. Better sell it on the Marketplace before you find yourself with another hobby...

Seriously, though, the oil can be cleaned off the aperture blades (once they are out of the lens) with lighter fluid, as in Zippo Lighters. You can either wipe them with a Q-tip soaked in the stuff (but be careful not to bend them or leave cotton strands), or just remove the blades completely and soak them in it.

There are tons of tutorials on the web outlining this for many different lenses. Your particular lens probably won't be explained, but find something similar and get to know the procedure. Then, as you take your lens apart, *take lots of pictures* so you have a visual reference of what it all looked like when it worked!

I'd bet you can get to the aperture assembly from the back, but you never can tell until you open it up. You'll have to remove some lens groups (which can be a tricky affair), but think twice if you find you have to remove the focusing helical or the zoom tubes. Some stuff is tricky to put back together...
Thanks for the great piece of advice. I have decided not to tinker further on the lens but to sell it cheap in marketplace with full disclosure. It is a shame! I am liking the lens for its strong build and unique character -- a lens that is not well known. Trap focus is not working in the test shots, I will zip in a foil for next shooting


cropped, catch-in (or trap) focus not working




Not exactly good picture, but given more time and catch-in focus enabled with foil, the lens has potential




When stopped down properly , it is quite reasonable in sharpness






Thanks,
Hin

Last edited by hinman; 03-16-2010 at 06:21 PM.
03-16-2010, 07:29 PM   #8
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QuoteOriginally posted by hinman Quote
In general, what are the methods and material used in cleaning aperture blades. How do you get it to dry? What sort of material to dry or re-lubricate the lens.
The lighter fluid (usually naptha) evaporates quickly so drying is not a problem. A few other solvents can be used. Mineral spirits works but the odorless variety evaporates slower so it's less effective.

The process would be a lot easier if the blades were not inconveniently located in the more-or-less center of the lens. A lot of lenses have a rear group that comes out in one piece and the blades are right there. I try that if I think the disassembly might be trouble - a zoom, for example. Cleaning is more efficient when you can get to both sides of the blades.

03-17-2010, 07:06 AM   #9
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Just want to point out that unless the lens is to be used on a screw-mount body oil in the blades shouldn't be a problem since the adapter pretty much negates the aperture pin. With stop-down metering sluggish blades is not going to be an issue.
03-17-2010, 03:44 PM   #10
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A monster of a lens Hin, and I agree with those people recommending 'just use it'.

Also, the oil makes for a much creamier bokeh :-)

I am curious so I start taking those back screws off a lens from time to time and then you have started something I can tell you.

Here's more advice on degreasing aperture blades,
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/75127-does-sti...tml#post762540

If tinkering is not a real hobby of yours don't ever start !
cheers, Georg
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