Google| Subject | Re: ISO value names are becoming ridiculous |
| From | Whisky-dave |
| Date | 01/06/2016 15:17 (01/06/2016 06:17) |
| Message-ID | <695a67cd-07bf-4aeb-a455-d2e63572e1aa@googlegroups.com> |
| Client | |
| Newsgroups | rec.photo.digital |
| Follows | Peter Irwin |
On Wednesday, 6 January 2016 14:07:11 UTC, Peter Irwin wrote:
Peter Irwinwhich is the same as the amount of light for a 'correct' exposure.
Sandman <mr@sandman.net>wrote:SandmanPeter Irwin
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:
It would be better to use Sv steps. 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.
I remmebr camera metting systems beign dexfribed as being able to go down to EV 1 or EV -2 which I found much easier to understand when comparing meter sensitivities especailly in the days of film.
01/06/2016-
