Monday, September 21, 2009

Oh, The Dreaded Highlight Blowout

Seems like everywhere you read you see pundits saying you have to preserve the highlights. I'll go along with that to a point. Those more knowledgeable than the self proclaimed authorities get it right. Saying you have to maintain the highlights is sort of like several other bastardizations of semi-well known quotes or phrases. On the early morning news program on ABC over the weekend the male host said the "computers get twice as fast and cost half as much every two years". The only part of that statement he got right was the part about "two years", and that's a modification of the original statement by Gordon Moore. Before Gordon got together with Bob Noyce to found Intel he was quoted as saying 'transistor density doubles every eighteen months (later modified to two years) with no increase in cost'. Computers get more capable, but not twice as fast. Things tend to get altered with use. Have you ever heard anyone say he(she) doesn't "cut the mustard"? Now, just how hard can that be? Mustard is typically a cream condiment. There's not much to cut. The actual term would be he(she) doesn't "cut muster". Muster, in this context, refers to a gathering of a military group for the purpose of inspection. If someone misses a muster, or fails a muster (doesn't pass the inspection) he/she might wind up in some serious trouble. The same alteration of the idea of not blowing out highlights is today topic. To find out if today's image has blown out highlights, hit the "read more".

The easy answer is yes, it does have some blown out highlights. Just not as many as you might think. You'll have to sort of take my word for it because I'm looking at the full sized image while you're looking at a "for the web" version. There's three distinct spots that have blown out pixels (pixels that register at 255, 255, 255). One is in the vertical line just below the glass in the lighthouse. There are eight pixels in that line with no detail. Another area is just beside the upper windows in the front of the house. That one has thirty six empty pixels. I blew the original image up to pixels level and counted them. The third area is on the right arch above the porch and has about six offending pixels. The image is as shot as far as cropping goes, so we have a twelve megapixel image with fewer than fifty pixels blown out. That's got to be a pretty good ratio.
The thing about not blowing out the highlights that some of the pontificators seem to miss is that they have to be "important" pixels. On the lighthouse, the glint is supposed to be white. If eight pixels go over the edge and have zero detail, oh well. You would need scientific instruments to be able to figure out which pixels have detail and which do not. I'm a lot more interested in looking at an image than I am doing a forensic analysis of it.
There's a saying, "all things in moderation". There has to be a limit on what the boundaries are in the images we look at. Is today's image a great shot? I've seen better, but it's one of the best I took at the time we were there. We'll be back up on the Maine coast in a couple of weeks. I don't know if we'll shoot Portland Head Light on this trip or not. Hopefully there will be some good skys wherever we shoot and we'll get a few decent shots. What we get will be what we print, that's about all you can do. If you're there on a good day, it's up to your skill to get a good shot. If you're there on a crappy day, aim your camera lower or at smaller details. There will still be good shots, just not the sweeping panoramas.