hi gareth,
thanks for the invitation.... maybe i find time to enter again some images,
i am very busy the last months and still i am, so i read often LL at night in some hotel....
about the dng files:
no, dng is not the pure raw data.
a sti mos or a mos or a cr file or whatever has not to be a real raw file, it already is a rendered raw data whcih than can be interpretated by the raw software,- the original raw data may consist a.e. ( in case of sinar ) in the camera in form of one or two files for each image, for making noise calibration of the file. this data is translated than in the "raw" file which is used by the company- software capture shop ( in case of sinar , but its thesame for all mf backs ).
the dng data may contain the same amount of information, or less info or even more than the companie- raw format ( which also is not raw as i described above ).
in the companie- raw file may be calculated in some noise reduction, some white or black references, some LCC or gain adjuster datas or centerfold corrections, which all are not done in the original camera raw data. so what seems to be raw often is not pure raw anymore.
e.g. to explain that in one detail:
what will happen in the highlights and its recovery by the raw develloper software is a very important feature which is determined by the data itself, or better by the "translation" of the original raw data to the readable data format as dng, sti, mos and so on.
e.g. you have the possibilities to cut all three channels as son one exceed "255", to avoid color shifts in the highlights ( as described some treats before from a leaf user.... read there what stephan "brumbaer" hess answered and you will know more about that phenomen ). the two not overexposed channels are not cut in the camera raw data, but something has to be done with this data, otherwise you will end up with unusuable color shifts as soon as one channel is overexposed.
so you either cut the two channels as soon one is overexposed
or you programm a more sophisticated data interpretations where you pull out information of the two or the one remaining channel and interpolate this data to the one or two outblown channels, in this you will get color- neutral info as long as one channel still holds some information ( easy describedm cause the things are complicate cause the color temperature is different, so what is equal info at 5500k is very different at 3000k ).
this renderings are not done by the raw sw , this has to be done in the file which is delivered to the sw. and the programing for things like that is not easy,- and the quality difference might be immense. in case of the described different highlight renderings it is in normal cases between one till two stops in the highlights, in extreme cases three stops. the raw data in every case contains the same information, but the form how it is translated in the so-called raw data ( mos. sti., dng or whatever) makes the difference.
the centerfold issue and color shifts over the image aerea are another examples.
this image issues can be removed by "translating" the raw data in the dng file and correcting them at the same time. so the cf or colorshift exists in the raw data in every case, but it is removed in the dng file by translating the data , e.g. stephans brumbaer software is doing that with the sinar emotion files. this software also writes corrected dng files which contain white reference files ( if you have shit them before ) , so the dng is 100% color neutral over the whole image field,- the raw data not.
all this things together create an usuable dng file, because a dng file which still contains color shifts ( flexcolor, c1 ) or centerfold issues is not usuable, at leats it does not make much sense to use it. and a dng file which cuts the highlights ( this are doing all except brumbaers sw ) need to be shot with much more care not to overexpose the shot, than you can shoot knwoing that you have allways enough space in the highlights even, if some red blinking in the display shows you that the clouds in the sky are "over".
i am sorry not to be able to speak better english.... in german it would be more easy to explain in an understandable form.....