Exposure compensation with 87mm extension tube

[robin_odland]

How much exposure compensation do I need with an 87mm extension tube (Mamiya

#2-for the RB-67)?

 

Thanks for the advise

[ilkka]

Depends on the lens you mount in front of it. And the amount of focusing extension you use (ie. lens focused at infinity or to its closest distance).

[robin_odland]

I am aware of the compensation that is required due to the focusing bellows, which should simply be in addition to the compensation needed due to the extension tube, I would think.

 

Does Mamiya produce a chart on this?

[jean-louis llech]

Here is the compensation table for Mamiya RB67 Pro SD, extension tubes and different lenses.<p>

<a href="http://www.mamiya.com/products2.asp?id=1&id2=15&id3=40&id4=429&id5=431">Close-up table</a><p>

The tubes are :<br>

No 1 = 45mm extension<br>

No. 2 = 82mm extension<br>

No. 1 + 2 = 127mm extension<br>

Probably the length of #2 is 82, not 87mm.<p>

 

I have another document about RB67, RB67Pro-S (non-SD) extension tubes. It's the manual for these accessories. I'll send it to you soon.<br>

Regards,<br>

Jean-Louis<br>

[jean-louis llech]

The file has been sent.

[Ed_Ingold]

You can calculate the effective f/stop (a') as follows:

 

a' = a*(f+e)/f

 

where a is the nominal f/stop, f is the focal length and e is the extension with the lens focused at infinity, using the same units of measure (e.g., mm).