> From: PDML [mailto:[email protected]] On Behalf Of Charles Robinson > > I was in a park in Nevada (Valley of Fire), the sun was setting, it was > getting difficult to see. I took some photos which came out OK - and > due to the ability to tweak white balance, exposure, etc, it looks like > the photos were taken at a regular time of day. > > But I was there, and I KNOW it was dark dark dark. > > Is there some sort of "exposure equivalence" table which can tell me > "how dark it really was" when I had to expose a frame at ISO 1250, > 1/13th of a second, at f/4.0? > > (link below if you care) > > http://charles.robinsontwins.org/photos/2012/vegas/content/IMGP5607_lar > ge.html >
You can find the exposure value (EV) for the particular iso, shutter speed and aperture that you used, but that only tells you how dark the meter thought it was. Without a reference value you're going to have to rely on your memory, and adjust the output by eye. Knowing the EV of the exposure is not going to help. It seems to me that your problem is the way you metered the scene. If you use a reflective light reading then the meter will assume that you're pointing it at a mid-grey scene and expose accordingly. If you then process it on auto settings you'll get a picture that's mid-grey in tone. To bring it back to what you know it to be, you either have to adjust it by eye, for example by deciding that it was 3 stops darker than the meter indicated, or you can include a reference object in one of the exposures, such as a calibrated grey card or colour target; you can then process that frame so that the target comes out with its calibrated values - all the other values fall into place around it; after that you should be able to synchronise the settings across all the frames that you shot without the target, but in the same light. You could instead use an incident meter, which will give you a reading for the light that's falling onto the meter's sensor through a mid-tone dome. If you then process it on auto settings you should get a picture that shows the conditions as you saw them, more or less. When I say 'auto settings' I'm thinking of a fixed reference post-process - something like Kodachrome, where you sent it away to be processed and, unless you'd given special instructions to the contrary, they put everything through the same process at the same time - in other words you had a reference standard at the processing time. Now that KR is dead and we are all using a series of Giant Electronic Brains to take & bake our chefs d'oeuvre, the notion of 'auto settings' has become more difficult, and I don't have such a process myself for Lightroom, although I could probably come up with something if I sat down and thought about it for long enough. As far as I understand it, pressing Auto in LR makes it come up with an average mid-tone across the frame. This is very useful for rescuing something that's gone horribly wrong, or which was in any case a mid-tone exposure, but in a situation like yours it would just turn night into day. So unless someone here replies with a KR-like reference process, you're left with either including a reference target in one frame, or/and adjusting by eye. Hope that helps. But it probably doesn't. B -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
