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Thread: Understanding the bellows factor - mamiya C330

1. Understanding the bellows factor - mamiya C330

My Mamiya C330f has a focus screen with markings and a needle so you can adjust the exposure for the bellows extension but i dont know how to make the correction. The marks are as follows - 1.5 - 2 - 2.5 - 3 I know this cannot mean 1.5 stops and up to 3 stops, can anyone help me understand how to adjust the exposure using those numbers?

2. The numbers translate thus :
1.5 = +1/2 f
2 = +1 f
2.5= +1.5f
3 = +2 f

3. Smudger, Paul Ron, Thank you both for the info and the link to the manual!

4. Originally Posted by Smudger
The numbers translate thus :
1.5 = +1/2 f
2 = +1 f
2.5= +1.5f
3 = +2 f
The steps are in 1/3 stops:

1.5x = +0.6 stop
2x = +1 stop
2.5x = +1.3 stop
and 3x = +1.6 stop

But when you can't set 1/3 stops, it indeed (almost) translates to the 1/2 stop list above.
Almost, because it would be 'closer' to round 1.6 down to 1.5, not up to 2.

5. Bear in mind that on the C330 models you have to 'program' the lens focal length using the ring on the side control, otherwise the moving index marker will be off. It's a neat enough idea, but I sometimes think the basic scales on the 'simpler' models are just as effective.

6. There is also a plastic paralax correction plate that fits under the focusing hood to give correct index marks for the 55 and 65mmwide angle lenses

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