>Subject: Re: : [PRODIG] CS-Any way of opening jps as 16bit files? > >...According to Bruce Frazer, the explanation is an human eye can't >differentiate more than 128 levels of grey, a 8 bit contain 256 levels >and a 16 bit contains 65 536 levels. > >I wonder how some of you can see the differences you are talking about >for some times now....
I think we need need to be clear about the reason why we might want to work in 16bit: As has been pointed out, there are limits to the number of shades of grey that we can differentiate and I accept that it could be even less than 8bit (at some parts of the range). The point is not that some people want to use 16bit to have more tones to make an image look better, it is to force the computer to work to a greater degree of accuracy while it is doing all it's calculations during the manipulation of an image. Just because we walk into a shop with �10 and buy a few items and come out with �5 does not mean we would be happy if the shopkeeper did not bother with the pence, especially as the items might be in pence. When we convert an 8bit grey image to 16 bit, initially yes there is new visual information in the image, however, 16bit gives us extra information in between (the greys we can see) which helps hold information once we start manipulating the image. For instance a pixel may darken by just a fraction but not enough for a whole 8bit step. In 8 bit this would stay at the original level whereas in 16 bit it could change. Now if we were to do further work that darkened that pixel by a fraction, it may be enough to make it jump (when converted back to 8 bit) to the new darker value, whereas this would not have happened if you had stayed in 8bit. Does this help? Nathan Gaydhani (BSc in Photographic and Electronic Imaging) =============================================================== GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
