- From: Chris Murphy <lists@colorremedies.com>
- Date: Mon, 15 Sep 2008 11:15:33 -0400
- To: David Woolley <forums@david-woolley.me.uk>
- Cc: www-style@w3.org
On Aug 31, 2008, at 8:47 AM, David Woolley wrote: > > Chris Murphy wrote: > >> This is precisely why photographers are encouraged to "expose >> right" meaning to the right side of a histogram, which are quarter >> tones and highlights. It is preferable to correct in post- >> processing what appears to be a slightly overexposed images. This >> results in a higher quality capture. > > In any system with quantisation, or other noise, I would have > thought it was self evident that one should maximise the use of the > dynamic range. However, my experience is that digital media > tolerate over-exposure very badly. I did state "what appears to be" not actually overexposed. A correctly exposed image on a digital camera is more exposed than if you were shooting chrome, but probably not as much as if you were shooting negative. > That I think is also self evident, as over-exposed values are hard > clipped, whereas underexposure simply results in increased noise. > That isn't to say that quantisation noise isn't a problem with > typical 8 bit storage formats. In my experience, for amateur use, > one, or even half a, stop over is unacceptable, whereas two stops > under is still usable. (Most scenes have some small highlights that > can reasonably be clipped, of course.) And you're determining correct exposure with a light meter? Or you're determining this 1/2 stop over, and 2 stop under anecdote with the camera metering itself? What is this camera and how old is it? It could also be that your camera's in-camera JPEG is adept at resurrecting dark images, and sucks really badly at dealing with slightly overexposed data. If it were possible to access the Raw data from such a capture, assuming the scene was metered and correct exposure determined, almost every time I would take 1/2 stop over than 2 stops under because there are simply more bits for tools to recover highlight data than shadow detail. Chris Murphy
Received on Monday, 15 September 2008 15:17:08 UTC