I only read as far as about half of your first sentence. I didn't need to read further as it was obvious you had missed the point of the question.
Jack --- On Mon, 4/5/10, Godfrey DiGiorgi <[email protected]> wrote: > From: Godfrey DiGiorgi <[email protected]> > Subject: Re: Define "blown out" :-) > To: "Pentax-Discuss Mail List" <[email protected]> > Date: Monday, April 5, 2010, 12:05 PM > On Mon, Apr 5, 2010 at 10:27 AM, Jack > Davis <[email protected]> > wrote: > > I'll offer mine the nebulous term by saying that if at > least some surface areas are rendered featureless by virtue > of being too bright, I'd consider those areas "blown out." > Many images can tolerate a certain amount of this condition, > but it's amount is the criteria and varies with each viewer. > Said areas must, of course, contain some available mask > detail which defines the surface. > > IOW, I'm not talking about an absolute ball of glare > wherein no detail is discernible. > > There's nothing nebulous about "blown out". Consider areas > of pure > white with no detail as Zone 9 on the Zone System > scale defined as > follows: > > Zone 0 – key black or pure black – carbon or photo > paper black. > Zone 1 – near black – shadows in faint light or rooms > without light. > Zone 2 – dark gray/black – only subtle textures are > visible. > Zone 3 – very dark gray – distinct shadow texture is > visible. > Zone 4 – medium dark gray – slightly darker “black” > skin, dark foliage > or shadows in landscapes. > Zone 5 – medium gray or 18% gray – darker “white” > skin or lighter > “black skin,” light foliage or the dark blue of a clear > blue sky. > Zone 6 – mid-tone gray – average “white” skin or > shaded areas in snow > on a bright, sunlit day. > Zone 7 – light gray – pale “white” skin, a concrete > walkway in sunlight. > Zone 8 – gray/white, near white – distinct highlight > detail, like a > white wall in sunlight or brilliant surfaces in flat > light. > Zone 9 – known as key white or pure white – pure white > paper or snow > in bright sunlight. > > (Normally I think of the Zones as being from 1-10, but > Ansel was a C > programmer and did a 0-based count ... ;-) > > So, by definition, anything you want detail in is "blown > out" if your > exposure has placed it above Zone 8 on the above scale. > > Since I've never seen any application use 16-bit number > scales to > describe pixel values, you can determine what areas of your > image are > "blown out" in Photoshop or Lightroom using either a > percentage scale > or an 8-bit pixel value scale and floating the cursor over > white-looking areas while looking at the information > display panel. > Presuming that the exposure did not go to saturation and > there is data > in those bright areas, you can place them in adjustment > using the > Exposure (aka white point) sliders. This table makes it > easy ... > > http://homepage.mac.com/godders/zone-system-numbers.jpg > > EG: you have a near blown out area in a photo that you want > to ensure > images with detail on screen and in your prints. Float the > cursor over > it in Lightroom and see that it is currently at about 94% > in all > channels (or in one of them if that is the significant > color of the > area). Nudge the Exposure slider in the negative direction > until it is > in the range of about 85-88% to set that as the brightest > point. Now > make adjustments with the mid-tone, black point and Tone > Panel to > bring the rest of the photo into line with a satisfactory > display. > > A certain amount of area at Zone 9 is fine, as long as it's > not where > you wanted to convey detail. Too much Zone 9 in an image > generally > looks bad. Another thing to be aware of is that many papers > and > monitor screens cannot display the full 10 zone scale very > well, or > have non-linear characteristics ... That's why calibration, > profiling > and testing for DR are essential to good quality image > display, > whether on screen or on paper. > -- > Godfrey > godfreydigiorgi.posterous.com > > -- > 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. > -- 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.
