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10-11-2014, 03:05 AM   #1
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SMC Pentax 6x7 Shift 1:4.5 75mm

Hi All,

I have the above lens and took it out today the first or time. The aperture ring is locked on f4.5. The rear ring moves very slightly and the blades do as well. What is the front aperture ring for which appears to be locked?
Hopefully it does not need a visit to my camera repairer.

Yours in anticipation.

10-11-2014, 03:36 AM   #2
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This lens works like the SMC Pentax Shift 28mm f23.5 lens for K mount.

One aperture ring has click stops on it and actually stops down the lens.

The other aperture ring turns between the fully open aperture and the aperture set on the first aperture ring. This allows you to set the desired aperture on the first ring and quickly change from the open aperture to the set aperture by turning the second ring. the reason for this is that the aperture is not coupled to the lens mount, so there is no way for the camera to move the aperture to the set value when an exposure is take.

Regards

Chris
10-11-2014, 08:30 AM   #3
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QuoteOriginally posted by gordon_l34 Quote
Hi All,

I have the above lens and took it out today the first or time. The aperture ring is locked on f4.5. The rear ring moves very slightly and the blades do as well. What is the front aperture ring for which appears to be locked?
Hopefully it does not need a visit to my camera repairer.

Yours in anticipation.
The 75/4.5 shift is a preset aperture lens

Here is a copy of the manual:

Pentax 67 75/4.5 Shift Manual pdf

Phil.
10-11-2014, 10:09 AM   #4
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So, this lens has a single diaphragm with two actuation rings?

10-11-2014, 05:38 PM   #5
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Original Poster
Hi All,

Thanks for the link gofour3. everything is alright on the lens now that I have read the instruction manual!

Regards.
10-13-2014, 09:12 PM   #6
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QuoteOriginally posted by desertscape Quote
So, this lens has a single diaphragm with two actuation rings?
Correct. The first preset ring you select the shooting aperture you want and set the actual aperture to f/4.5.

After focusing, you turn the aperture ring until it stops at the previously selected “preset” aperture.

Would have been easier/better to make this lens a straight manual diaphragm lens and remove the preset ring. The K28/3.5 Shift works the same way.

Phil.
10-14-2014, 05:57 PM   #7
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Thanks Phil; that is one of the few lenses that I have never owned.
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