Google| Subject | Re: ISO value names are becoming ridiculous |
| From | Peter Irwin |
| Date | 2016-01-06 15:04 (2016-01-06 14:04) |
| Message-ID | <n6j6t6$hgt$1@dont-email.me> |
| Client | |
| Newsgroups | rec.photo.digital |
| Follows | Sandman |
| Followups | Whisky-dave (13m) Sandman (1h & 22m) > Peter Irwin |
Sandman <mr@sandman.net>wrote:
SandmanIt would be better to use Sv steps.
So with the D5, it can boost its ISO to ISO 3,280,000, and suddenly how ISO is named is becoming just stupid. We should use EV steps instead:
Ev is from the EVS system it means exposure value, and is the sum of Av (aperture value) and Tv (Time Value).
F/stop f/1 f/1.4 f/2 f/2.8 f/4 f/5.6 f/8 f/11 f/16 Av 0 1 2 3 4 5 6 7 8
Speed 1 1/2 1/4 1/8 1/15 1/30 1/60 1/125 1/250 1/500 Tv 0 1 2 3 4 5 6 7 8 9
Hence a exposure of 1/125 at f/16 has a Av of 8, a Tv of 7 and an exposure value of 15 (8+7).
This system has been in use since the 1950s. There was an expanded system proposed in the 1960s called APEX which also had light values (Lv) and film speed values (Sv) such that Sv + Lv = Av + Tv = Ev. It is a good system and worth learning. It would have been a good idea if more exposure meters had had light value readings, people sometimes get the funny idea that Ev is an amount of light, but it is actually an amount of exposure. The Ev reading on an exposure meter will read Lv light values when set to ASA 3.
ISO(ASA/DIN) (Speed Value) 3/6 0 6/9 1 12/12 2 25/15 3 50/18 4 100/21 5 200/24 6 400/27 7 800/30 8 1600/33 9 3200/36 10 6400/39 11 12800/42 12 25600/45 13 51200/48 14 102400/51 15 204800/54 16 409600/57 17 819200/60 18 1638400/63 19 3276800/66 20
Peter. -- pirwin@ktb.net
2016-01-06-
