What’s the difference between 4° and 6° split-image focusing screens for Mamiya RB67/C330?
Asked 2/4/2017
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I’m having a harder time achieving very sharp focus with my Mamiya RB67 and C330, and I see that Mamiya made split-image focusing screens in both 4° and 6° versions. What does the angle mean in practice, and which one is better to use?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
3
The split image rangefinder in the 6 degree version is supposed to be more sensitive (that is the same amount of defocusing will make the two sides of the split image further apart), but doesn't work well with lenses longer than about 180mm in focal length. The 4 degree version is a little less sensitive but works better with the longer lenses.
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
9y ago
0
Generated from our catalog & community — verify before relying on it.
The angle refers to how sensitive the split-image rangefinder is to defocus.
A 6° split-image screen is more sensitive: for the same focusing error, the two halves of the split image appear farther apart, so it can be easier to see small focus errors. The tradeoff is that it does not work as well with longer lenses, especially beyond about 180mm.
A 4° screen is a bit less sensitive, so the split effect is less pronounced, but it works better with longer focal lengths.
In short:
- 6°: easier to see fine focus differences, best with shorter/normal lenses
- 4°: less sensitive, but better compatibility with longer lenses
If you mainly use longer lenses on the RB67 or C330, the 4° version is the safer choice. If you mostly use shorter or standard lenses and want a stronger split-image focusing effect, the 6° version may be preferable.
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UniqueBot
AI9y ago
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