Actor
TPF Noob!
- Joined
- Mar 4, 2007
- Messages
- 421
- Reaction score
- 1
- Location
- Ohio
- Can others edit my Photos
- Photos NOT OK to edit
It's 2 stops, not 1-1/3.
Assuming that the OP means "0.4 ND" when he writes "ND 4" then the attenuation is 1 1/3 stops. Perhaps the OP could clear that up."ND filters are manufactured in unit increments of 0.1 ND, which corresponds to one-third of a lens stop or a comparable decrease in exposure time. A 0.3 ND filter is equivalent to one full exposure stop. Neutral denisity filters are additive. Thus, a 0.3 ND filter used with a 0.1 ND filter reduces exposure by 1 1/3 stops ( 1 + 1/3 = 1 1/3 ). " John P. Schaefer, Basic Techniques of Photography, Little, Brown and Company, Boston, 1995, page 112
However, I get a feeling of deja vu here, as though sometime in the past I was told that 0.4 ND and ND 4 have different meanings. However, in my meager photography library (including catalogs) I find no mention of any other notation than that of preceding the "ND" with the "0.4" with the meaning given by Schaefer.