- From: David Woolley <forums@david-woolley.me.uk>
- Date: Sun, 13 Jul 2008 00:12:35 +0100
- To: www-style@w3.org
- CC: Chris Murphy <lists@colorremedies.com>
Chris Murphy wrote: > > An image with no encoding ("gamma 1.0") or linear encoding would look > completely washed out. I think it would be obvious to anyone with vision > that there is a serious problem so I'm not sure how big of a problem > this really could be unless people just aren't paying attention. Example of images that are clearly gamma 1.0, and have been for several years, in spite of my pointing out the problem, and their being obviously wrong, supplied off list. > I know if no camera that does this. Digital cameras all do have linear > response to light, and record it that way. The raw data is processed in > the camera, tone mapped where it has a tone reproduction curve defined > by either the sRGB curve or gamma 2.2, and is then JPEG compressed and > tagged with EXIF data as to its color space. Example of image which is clearly gamma 1.0, but has metadata (as decoded by Wikipedia) claiming sRGB colour space also provided off list. This example is from a Panasonic camera. Although it is possible that the image was retouched without correcting the metadata, all the indications are that this image wasn't retouched, and I would expect an image to be deliberately retouched to gamma 1.0, except for deliberate effect. More generally, the number of images with bad gamma on the web, particularly non-professional ones, is sufficiently high that I think there must be quite a few digital cameras which don't correct to sRGB, although many may well either not specify a colour space, or identify it correctly. I don't think all can be attributed to scanners, which are also quite likely to produce gamma 1.0 images in untrained hands. (On the other hand, both my current Olympus and my very first, Jenoptic, do correct to sRGB, although the Jenoptic doesn't provide metadata and I'm not sure whether the Olympus encodes colour space.) I've not quoted the first URL because it belongs to a small organisation with which I'm sympathetic, and don't want to criticise it publicly. The other is on Wikipedia, but I've extended the same courtesy. If anyone else wants to know the actual examples, ask me off list. -- David Woolley Emails are not formal business letters, whatever businesses may want. RFC1855 says there should be an address here, but, in a world of spam, that is no longer good advice, as archive address hiding may not work.
Received on Saturday, 12 July 2008 23:11:22 UTC