John,

As the PD finder meters through the lens, it takes into consideration the light loss through the tube and no compensation is needed. However, if using a handheld meter, compenasation will be required.

By John D. Mcleish on Monday, June 07, 2004 - 04:32 pm:

When using Extension Tubes, do I have to add one stop for each tube used to the reading I get for the exposure compensation factor in the Close-up Table?

By Alan on Monday, June 07, 2004 - 09:53 am:

John,

As the PD prism is TTL it will take into consideration the light loss through the tube without any problem. Do not forget that the shutter speed and aperture have to be manually transferred to the camera.

By John D. Mcleish on Saturday, June 05, 2004 - 09:53 pm:

Can I use an RB67 PD Prism Finder on a 180 mm Lens coupled with Extension Tube NA701 (45 mm) to find the correct exposure and shutter speed?

By Nick on Wednesday, May 26, 2004 - 12:21 pm:

Thanks a million.. Am looking for one on e-bay, so I'll hold out for a PD.

By martink on Wednesday, May 26, 2004 - 10:27 am:

They were good in their day! Some could be 30 years old. Cds meters were ok in medium light ranges but are not as accurate in low and high light levels. PD prisms tend to be good in all light levels.
You also have to bear in mind that spares (should the unit need them now or in the future)are getting thin on the ground for cds finders.

By Nick on Tuesday, May 25, 2004 - 02:40 pm:

Thanks!

But are the CDS prisms any good? There seem to be more of them available on ebay, and less PD's.

By martink on Monday, May 24, 2004 - 04:59 pm:

There have been a number of RB prisms made over the years, the PD prism is more accurate than any of the cds versions.
There have been a number of different casings. Some of the very early ones may have even had metal casings!

By Nick England on Monday, May 24, 2004 - 11:48 am:

Can anyone tell me the difference between the newer, shiny plastic looking Mamiya RB67 PD Prismfinders with built in lightmeter, and the older, CDS style, more chunky looking RB67 TTL meter prisms, which look to be made from a more sturdy material?