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12-05-2008, 10:57 PM   #1
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Unique SMC Pentax-AF 35-70/2.8

Hey guys, thought you might be interested in a slight modification that I made a couple weeks ago. I acquired this lens along with an ME-F body in hopes of having a little fun with the ancient autofocus mechanism when these two are coupled. However, upon inspection, the ME-F had a horrible case of corrosion, batteries had etched away the traces on the circuit board connecting power to the system (I could get it to power up if I directly connected 6V in the correct location, so the camera still worked fine, just bad contacts).

So I decided to have a little fun with this awesome fast lens, which really does produce very nice images when compared against similar zooms (I'm thinking the SMC Pentax-A 35-70/4, which is very good in it's own right).

So out came the tools. About an hours later, out came a new lens! I completely disassembled the lens, removed all of the autofocus mechanism & wiring. I added some grease to the helical to achieve a damped manual focus action. After reassembly of the lens and verifying that it still worked, I pulled out the trusty dremel to remove the metal mount that supported the AF motor and battery compartment. I made sure to tape off any spots where metal shaving would try and sneak into the lens--I think I did a good job and avoiding anything getting in while I was hacking. I also re-cut the rubber grip so that it would sort of fit on the newly designed lens.

Now I've got a reasonably sized and decent looking 35-70/2.8. The MF is still somewhat difficult since the focusing ring is so small. But the focus action is pretty nice now that I greased it up, and it isn't too difficult to achieve the right focus, even with the small 1/4 turn travel of the focus. My main complaint about this lens is the ~4-ft min focus distance, so you can't really do any close-ups with this lens. But other than that it's nice, and it has the beautiful red coating that is unique to this lens (or so I hear).

Here are some shots of the modified lens:











12-05-2008, 11:05 PM   #2
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Yikes! It's been lobotomized!

Steve
12-06-2008, 07:07 AM   #3
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great job

Wow........
You have done a great job. Can you post some pictures taken with this lens?
Thanks,

Subho
12-06-2008, 07:26 AM   #4
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oh my freaking god.... what the hell have you done? I would have bought that from you no questions asked. jeez what a waste.

12-06-2008, 07:38 PM   #5
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It's not a waste. The lens still works great. It's not like the autofocus system was of any real use (other than historical or collector value, but the lens wasn't quite perfect for collecting), even on the ME-F I hear it was pretty horridly slow and requires extremely high contrast to work correctly. So I did this lens a favor and slimmed it down and made it more suitable for manual focus!

I can take a few shots with this lens and post them soon. It's dark so they'll be indoors under incandescents. Maybe I could do a few outside tomorrow. I'll probably post a few examples later tonight.
12-06-2008, 10:44 PM   #6
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I bet you are using the Holy Grail as a spittoon!
12-06-2008, 10:56 PM   #7
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I think you've done a great job. Is it possible to remove more to get better access to the focus ring?

Go shoot and enjoy.
12-06-2008, 11:10 PM   #8
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QuoteOriginally posted by Light_Horseman Quote
I think you've done a great job. Is it possible to remove more to get better access to the focus ring?

Go shoot and enjoy.
Yea I could take off a big more, particularly where you can see the harsh corner where the battery/motor mount used to be. That square sharp corner isn't very comfortable. I could probably at least take that down to an angle and make it much more comfortable to use.

Right now the section that was removed that gives greater access does improve the grip on the focus ring, but I could definitely make it a little better without hurting anything. Can't take off too much b/c then you end up exposing the helical (as seen in one of the photos when focusing at the min distance). I guess that doesn't matter too much as long as you don't get any debris lodged in there.

I'm going to try and take it out for a spin tomorrow (decided that inside shots aren't very exciting)

12-07-2008, 06:16 AM   #9
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I have an ME F and have been looking for this lens at a reasonable price. so for me it is a waste. there aren't that many out there, and it seems rather ridiculous to chop it up.
12-07-2008, 04:16 PM   #10
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Here are some test shots from a reunion/christmas party that I was at earlier today. I tried out a few different lenses, but tried to get in plenty of shots with the SMCP-AF 35-70/2.8 to get a few on here for you guys to check out. I wanted to get more outdoors, but since I was stuck indoors I decided to make do.

The venue was a church fellowship hall with flourescent lighting and some windows. It was pretty bright outside which let in some decent light, but also created some problematic flare when shooting w/ a window in the background.

Was shooting at ISO800 on my K200D, a good compromise b/t noise and and shutter speed. Could shoot at about 1/60" or so with those settings. Most of these were shots wide open, maybe all of them.

1. Father-in-Law + wife (I'm a youngin' at 24)...a little bit soft due to slighty OOF


2. Christmas Decorations. Colorful.


3. I know some don't like baby pictures, but hard to avoid. So here' my relatively new nephew-in-law. Nice and sharp.


4. Must have been interesting!


5. Flare from the window


Here are a few test shots to show different between wide open and down to f/8 I think. I stepped outdoors from the reunion to snap a couple for you guys. First shots are wide open, second are closed down









Last edited by arpaagent; 12-07-2008 at 07:34 PM.
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