[Lenscap]

I searched for this topic, and failed to find anything. If it's there and I missed it, point me to it and accept my apologies.

I've acquired a Pentax bellows, and have been playing with it a bit, on a KX (not K-X) and a K1000.

How do you meter? The lens is separated from the body, so the open-aperture metering doesn't work. If I understand my physics correctly, the f-stop depends on focal length, which varies with bellows extension, so I can't just plug in, say, f4 into an external meter and call it good.

Am I missing something? Making it harder than it should be?

Your wisdom and advice are appreciated.

[Adam]

I searched for this topic, and failed to find anything. If it's there and I missed it, point me to it and accept my apologies.

I've acquired a Pentax bellows, and have been playing with it a bit, on a KX (not K-X) and a K1000.

How do you meter? The lens is separated from the body, so the open-aperture metering doesn't work. If I understand my physics correctly, the f-stop depends on focal length, which varies with bellows extension, so I can't just plug in, say, f4 into an external meter and call it good.

Am I missing something? Making it harder than it should be?

Your wisdom and advice are appreciated.

Well, since the lens has a manual diaphragm when placed on a bellows, you can still go by the camera meter's reading. The viewfinder will just darken as you stop down, so you should wait to meter until you've focused and composed.

[TwoUptons]

Some bellows have a double cable release. One trips the camera and the other stops the lens down.

The idea is that they are timed such that pressing the release stops the lens down and then snaps the shot.

If you have one of those, you'll need to trip the lens somehow to meter/shoot at anything other than wide open. A regular cable release will do the job.

-Eric

[wombat2go]

I've acquired a Pentax bellows,

Metering depends on the Pentax Bellows model.
Assuming it is K mount,
Model "Auto Bellows M " and the later "Auto Bellows A/m" had the mechanics for open aperture metering unless the lens is reversed.

I have the basic "Bellows Unit 3 " which does not have coupling for open aperture metering.
So it has the issues you mention.
But so far I only used it with the digital cameras, so just use the stop down "green button"
https://app.box.com/s/fdee986cccb6ea2d08cd

You might be able to download the instruction manual for the bellows version you have.

Edit: I learn something here, the photo shows I have the "Auto Bellows M" which can have open aperture metering with the cable mentioned by TwoUp, and I don't have that.

[Lenscap]

Well, since the lens has a manual diaphragm when placed on a bellows, you can still go by the camera meter's reading. The viewfinder will just darken as you stop down, so you should wait to meter until you've focused and composed.

That's the thing, though. I can go from 1.7 to 22 with no lightening or darkening, and no change in the camera's indication of correct exposure. I assumed the mount on the bellows was depressing the aperture arm thing (forgive my ignorance of the correct nomenclature) and keeping the blades open, as if it had been mounted to the camera.

---------- Post added 09-16-16 at 07:22 PM ----------

Metering depends on the Pentax Bellows model.
Assuming it is K mount,
Model "Auto Bellows M " and the later "Auto Bellows A/m" had the mechanics for open aperture metering unless the lens is reversed.

I have the basic "Bellows Unit 3 " which does not have coupling for open aperture metering.
So it has the issues you mention.
But so far I only used it with the digital cameras, so just use the stop down "green button"
https://app.box.com/s/fdee986cccb6ea2d08cd

You might be able to download the instruction manual for the bellows version you have.

Edit: I learn something here, the photo shows I have the "Auto Bellows M" which can have open aperture metering with the cable mentioned by TwoUp, and I don't have that.

Mine says: Asahi Pentax Bellows Unit K. No place that I can find for dual cable release.

I'll try to find the manual somewhere.

[LesDMess]

That's the thing, though. I can go from 1.7 to 22 with no lightening or darkening, and no change in the camera's indication of correct exposure. I assumed the mount on the bellows was depressing the aperture arm thing (forgive my ignorance of the correct nomenclature) and keeping the blades open, as if it had been mounted to the camera.

---------- Post added 09-16-16 at 07:22 PM ----------



Mine says: Asahi Pentax Bellows Unit K. No place that I can find for dual cable release.

I'll try to find the manual somewhere.

Here is a picture of my Pentax Auto Bellows K with the dual release cable plugged in.



Where it is plugged in the front will stop down the lens first then fires the shutter next.

[Lenscap]

Crappy cell phone pic of mine. It doesn't say Auto Bellows, which may be the difference.

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[Not a Number]

The manual for the Bellows Unit (K) can be downloaded from the Ricoh Canada site:
http://ricoh-imaging.ca/pdf/o_manuals/om_BELLOWSUNIT_e.pdf

The aperture should change as you turn the aperture ring. If it stays wide open you may have the Auto Bellows K as pictured above. Either attach a cable release as above or you can press in the button with the cable socket which will stop down the lens. The button should lock by twisting it when you press it in. You can use a standard cable instead of a dual cable. Just lock it to keep the aperture closed when you shoot.

Model "Auto Bellows M " and the later "Auto Bellows A/m" had the mechanics for open aperture metering unless the lens is reversed.

Actually with the Auto Bellows you can reverse the lens by reversing the front standard so the aperture stop down coupling will still work.

[wombat2go]

Actually with the Auto Bellows you can reverse the lens by reversing the front standard so the aperture stop down coupling will still work.

Thanks,
See, I learn something every day on PF, today I learned 2 things

[Not a Number]

Thanks,
See, I learn something every day on PF, today I learned 2 things

It's quite cleverly designed. Loosen the thumbscrew where the bellows connects to the front standard. There is a 49 to 52mm step-up ring in case you are using a 49mm filter ring lens. Remove the big front screw, reverse the standard. Replace the screw, reconnect the bellows to the front of the lens. The rear elements remain recessed and somewhat protected and there are filter threads should for some reason you want to use a filter. The Minolta Auto Bellows III goes one step further in that the front standard pivots around without having to reverse the whole thing. But they didn't incorporate the step-up ring into the bellows.

[Lenscap]

The manual for the Bellows Unit (K) can be downloaded from the Ricoh Canada site:
http://ricoh-imaging.ca/pdf/o_manuals/om_BELLOWSUNIT_e.pdf

The aperture should change as you turn the aperture ring. If it stays wide open you may have the Auto Bellows K as pictured above. Either attach a cable release as above or you can press in the button with the cable socket which will stop down the lens. The button should lock by twisting it when you press it in. You can use a standard cable instead of a dual cable. Just lock it to keep the aperture closed when you shoot.



Actually with the Auto Bellows you can reverse the lens by reversing the front standard so the aperture stop down coupling will still work.

Thanks for the link. I'll download the manual and see what I can figure out.

[wombat2go]

It's quite cleverly designed. Loosen the thumbscrew where the bellows connects to the front standard. There is a 49 to 52mm step-up ring in case you are using a 49mm filter ring lens. Remove the big front screw, reverse the standard. Replace the screw, reconnect the bellows to the front of the lens. The rear elements remain recessed and somewhat protected and there are filter threads should for some reason you want to use a filter. The Minolta Auto Bellows III goes one step further in that the front standard pivots around without having to reverse the whole thing. But they didn't incorporate the step-up ring into the bellows.

Here is the Pentax "Auto Bellows M" with the lens reversed according to the above instructions. Lens is SMC Pentax 1:2 55mm which has a 52mm front.

[UncleVanya]

With the lens in your hand not mounted does the aperture stop down as you twist the aperture ring? Sometimes lenses get stuck.

[Lenscap]

With the lens in your hand not mounted does the aperture stop down as you twist the aperture ring? Sometimes lenses get stuck.

Yes, the aperture blades move exactly as they should.

[Not a Number]

Could you take a photo of the lens mount on the bellows from the front, e.g. looking into the bellows. Perhaps someone had modified the mount to open the aperture. Why one would do this I don't know. Unless they wanted to use lens without aperture rings. You can stop down by unlocking the lens and turning it in the mount.