Extension Tubes for RB67...

abruzzi said:

doesn’t the rb have some linkage to stop the aperture down when you Fire?

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I only played with it for like 30 minutes last night, but I'm sure it has to since there's no way to manually stop down the lenses...at least I don't think there is.

But more imporantly, does the RB have some sort of support bracket when using the tubes? Seems like a lot of weight to hang off the single lens mount.

ChristopherCoy said:

I only played with it for like 30 minutes last night, but I'm sure it has to since there's no way to manually stop down the lenses...at least I don't think there is.

But more imporantly, does the RB have some sort of support bracket when using the tubes? Seems like a lot of weight to hang off the single lens mount.

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For manual stop down, use the Depth of Field preview lever on every lens (see page 10 of the manual).
The lens mount is designed to support the 360mm f/6.3 lens without a support bracket, so I doubt that an extension tube plus a 180mm lens would bother it.
If you are concerned, there was a support bracket for the 500mm f/8 lens!
By the way, while you can use extension tubes with the 180mm lens, most would ask why?

MattKing said:

By the way, while you can use extension tubes with the 180mm lens, most would ask why?

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Just to say that I did I guess. I put the 65mm on it first and couldn't figure out why I couldn't get anything in focus. Turns out you have to put the 65mm about 1 inch away from your subject. I then put the 180mm on it and focused on Kenny's eye. It was rather interesting to see his pupil that large in the viewfinder. You could see every little string of color. But after having both the 65 and the 180 on the camera with both extension tubes, I'm figuring I'll always use the 65mm. It seemed easiest.

It is really difficult to light your subject with the 65mm - your own/the lens and camera's shadow really gets in the way.
There is a reason that the macro lens for the system is 140mm.

Can someone post examples of photos shot with the 45mm tube, and the 82mm tube individually? I’m trying to get an idea of when/what each should be used for individually, and also stacked. Could you please also mention which lens you used?

Have you looked through the instruction manuals you have for "Mamiya RB_Ext_Tubes_non-SD.pdf" - it includes all sorts of information about things like working distances, magnifications and fields of view?

MattKing said:

Have you looked through the instruction manuals you have for "Mamiya RB_Ext_Tubes_non-SD.pdf" - it includes all sorts of information about things like working distances, magnifications and fields of view?

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Not yet.

We left this morning for a week in north Texas and I brought the tubes with me. I’m hoping to try and use them around the farm and the nearby state park.

...a couple of observations:

1. RB tubes contain some moving parts to transfer motion from the firing/cocking disc in the camera body to the lens or even another tube. With a lot of wear and tear these moving parts can develop slack and fail to operate properly.
2. There's no particular order for fitting/dismounting tubes, although it's normal to fit 'cocked to cocked'. I've never known a tube get stuck on a lens.

While I'm sure the manual has things like "this lens with this extension can focus this close." but you don't really need that. Pick a lens, mount it direct to the camera and focus as close as you can so the lens is racked as far out as possible. Then watch the viewfinder as you walk closer to an object. When the object is in focus, that is your minimum distance with no extension. If you're shooting anything with that lens that is further than that distance don't use an extension--lets say 30 inches or greater. Next attach the shortest extension to the lens and still with focus racked all the way out, do the same thing--lets say it lets you to 15 inches. So use that extension for anything from 15-30 inches. Do that for all your extensions and you should be able to come up with a simple table: infinity to 30": no ext; 30-15" ext-1; 15-8" ext-2; etc. If you lke you can also eyeball the object size if you want to know the magnification as well.

The thing to remember is extension tubes affect close focus distance, that it. Because the size of the object in the viewfinder is directly affected by how close you are, reducing the minimum focus distance effectively allows you make object larger. Since they are just empty tubes, they don't change the optical properties of the lens, they just allow it to focus closer than you normally would.

One other thing to remember is if you are using an external meter to get exposure, you may need to calculate the so-called "bellows factor", thanks to the inverse square law, the further you move the lens from the film, the less light falls on the film. When you get to 1:1 you need to increase exposure by 2 stops. If you are using a TTL meter, then you don't have to do that because the internal meter already sees the reduction in light and will give the correct exposure.

Well then maybe I need to develop normally. I put the 65mm on with the 45mm tube and shot a roll. I metered it at ASA 80 at F8 and 1/250. I was concerned that I over exposed the TriX 400, but maybe because the bellows were racked out all the way then I exposed normally.

i shot it at 80 because I thought it was one of my 1976 expired rolls.

Yeah, its something most 35mm and digital macro shooters usually don't know becuase the build in meters on those cameras mean they can remain blissfully ignorant of the drop in light levels. Technically the light drop begins the moment you focus closer than infinity, but in the focal range of most non-macro lenses it is small enough that you don't have to worry.

I’m a true “man” and don’t read directions. I knew about the compensation needed which is why the dang scale is printed on the side of the camera. I just didn’t think about it. I prefer to just throw tools at things, mess up a few things, and THEN go back and read directions. Lol

I’m going to have to make a little laminated wallet card with a check off list.

With an RB67 and wide lens, you sometimes need to apply bellows factor even without an extension, but you likely always need it when you have a tube mounted. Look at it this way: with the 50 mm lens, no extension, but bellows all the way out, you're already close to 1:1 and you need two stops of extra exposure right there. Add 45 mm of tube, and you're close to needing three stops.

This is partially a bad example, because Mamiya doesn't recommend going past 1:1 with the 50 mm lens, but it makes the calculation easier...