Help with exposure compensation

[MrScott]

Hello all.

A while ago I found an old Practika 35mm SLR with some extension tubes, so I'm wanting to have a go at some macro work (My other camera is a Powershot S2 IS so it can't do proper macro). I've got 2 extension tubes and a Galaxy vario converter I found with the camera, but the light meter isn't TTL so I need to work out how much I'm going to need to compensate exposures. This is what I've got:

I'll be using them with a 50mm lens. I've found the maths to work it out for the extension tubes, but I don't know how the converter will affect things. If anyone could help or point me in the right direction it'd be much appreciated, I'm new to this manual 35mm stuff

 

[MrScott]

Hi, thanks for the help. Those are pertty much the maths I found for it here so it sounds right, sometime today or tomorrow I'll work it all out and take some shots. I'll calculate using the overall extension of the tubes / converter I'm using, then also bracket a couple of stops each way and see what comes out best. I'll make sure I let you know when I (eventually) get the film developed and see how they come out.