Trouble With 120mm Soft Focus on P645N

[Tom Taylor]

Anyone familiar with the following problem that can give me some advise?

Yesterday was the first time that I tried using a Pentax 67 120mm Soft focus lens on my 645N. After one or two frames, the camera's "low battery" indicator goes on, the mirror locks up, and the film rewinds. I use a Pentax 67 to 645 adaptor. After experimenting with several rolls of film I have found that it only does this with the 120mm Soft Focus lens - other Pentax 67 lens work fine - and only when there is a roll of film loaded. If the film back is empty, it works fine - the shutter opens and closes, mirror goes up and down and the camera whirs as normal.

I thought that possibly the 67 120 soft was not designed to be used with the 645N as it is not an automatic lens but I downloaded the 120's brochure from Pentax and it's supposed to work.

Any ideas?

Thanks,

Thomas

 

[yurihuta]

Hey Thomas,

Quite strange. The 67 - 645 adapter does not transmit anything to the camera body in terms of electronic signals - it is a 'dumb' mount. Unless there is some other adapter out there (I have the Pentax made one) or I am completely forgetting how this works. So, I think that could be ruled out as the cause. You did mention this was your first time with the 120mm soft focus lens, could it be a coincidence that the batteries were worn down as well? Worn down enough to fire off a couple of frames and then have momentary voltage anomaly to trigger the rewind?

Just some thoughts.

Yuri

 

[Tom Taylor]

Thanks for the reply Yuri.

My first thought yesterday was that it was the batteries even though they were relatively new. I thought that I may have gotten' a bad set. So I went to a nearby Walgreens and bought an 8-pack (they were on sale at 2 for 1). Wasn't the batteries.

This morning I ran a roll of film with a 645AF lens attached. No problem. Then I ran a roll with a 55mm P67 lens. No problem. Then I put the 120Soft on and it happened. If I dismount the 120 w/adapter and reattach and fire the shutter button, the mirror resets and the low battery indicator goes off. I can fire off 8 frames with the 55mm or 75mm 67 lens attached with no problems and then switch to the 120mm, then it occurs again in 1 or 2 frames.

I read in the Pentax literature I downloaded this morning that using either of the Pentax rear converters is recommended with the 120mm soft. So just now I loaded the camera with a roll of film and fired off ten frames with the 120 attached to a T6=2x Pentax rear converter. No problem. Then I removed the converter and the camera rewound on the 15th frame. It's not the 67 - 645 adaptor (a Pentax in my case) which I have used on the P645N with several 67 lens without a problem and not the batteries. There is something wrong with the 120's bayonet mount - it does fit on tight. Otherwise both the lens and adaptor are in mint condition.

Looks like I'll have to use a rear converter when using this lens on the 645 which Pentax says "offers far more degree of soft focus than when not (using ther converter)."

 

[yurihuta]

photo.net has a thread from 2002 that has someone saying they use the 67 120mm soft focus lens on a 645 body with the Pentax adapter without mentioning the problem you are experiencing.

Is there any play once the lens is on the adapter? or does it feel too tight relative to the other 67 lenses?

 

[Tom Taylor]

Nope, no play. It goes on and off just like the rest of the 67 lens and the spacing between the bayonets looks the same.

One thing that I just noticed/remembered: When the camera rewinds with the 120 soft, the little lever inside the camera that closes the shutter is all the way down as if the depth of field review lever on the outside of the body was depressed. Since the 120 soft is a manual lens, there is no connection on the lens that can make contact it. It pops back up when the 120 is dismounted from the body and the shutter button depressed which also turns off the low battery indicator and brings the mirror down.

 

[yurihuta]

Could it be the sequence of steps is different? Do you consistently take the same steps?

e.g. mount 67-645 adapter to body -- then mount lens to adapter

or do you sometimes mount the lens to the adapter and then to the camera?

It is puzzling... since there is no direct connection between the 67 lens and the 645 body.

 

[Tom Taylor]

No. I usually mount the adaptor on the camera and then the lens on the adaptor and then the reverse when dismounting. It's easier that way. I bought the 645N used off E-bay about 3 years ago to "replace" the 35mm. Since I also have the P67II w/11 lens it seemed the smart thing to do as I wouldn't have to purchase lens just the 67 to 645 adaptor. I have used all 67 lens with it - ranging from 45mm to 400mm - without any problems. But this was the first time I used a 120 Soft on the 645N.