more RAW vs JPEG (1 Viewer)

Recurvirostra said:

If 5% of your theoretical JPEG is blown-out you will have far less blown-out pixels in the RAW because it has many more brightness levels below pure white in which to store the detail, before you reach the next level down in the JPEG file (one gradation below pure white).

In real life, even if the photo is not perfectly exposed, whatever area is blown-out in the JPEG will be much smaller in the RAW because the RAW file has a whole bunch of levels below pure white, but still brighter than the JPEGs second brightness level, in which to store detail.

Click to expand...

Ahhhh ... now I understand where you are making your error. You are assuming that the 8-bit value of 256 represents 30 values (4066-4096) in a 12-bit file. This is not correct. This top value is used to represent blown out pixels and nothing else. 256 = 4096

255 may be used to represent 4065-4095 or something similar. In reality the exact numbers assigned does vary from one RAW converter to another (and from one model camera to another) but usable data (above 0 and below the maximum) is never discarded, just compressed.

Levels detail is lost in this average 30 to 1 compression without question. But pixels don't drop to 0 or become blown out because of it. The people who write the RAW converters are smarter than that!

I came into this knowledge from quite a number of sources over time. A couple of websites that give a little insight into this subject are:
http://www.dpreview.com/learn/?/key=ad_converter
http://www.luminous-landscape.com/tutorials/understanding-series/u-raw-files.shtml

Well, Jim, all I can say is that since I started using RAW for all my bird photography (with the same camera), I have had far less trouble with blown highlights than with my previous use of JPEG. And it seems that many other photographers, rightly or wrongly, seem to be saying a similar thing.

It's interesting that you quote the same link to Luminous Landscape to prove your point that I used in post #38 to prove mine. |=)|

The important thing is that, whatever method each photographer uses to obtain the results they're happy with, is the right one for them.

Recurvirostra said:

Well, Jim, all I can say is that since I started using RAW for all my bird photography (with the same camera), I have had far less trouble with blown highlights than with my previous use of JPEG. And it seems that many other photographers, rightly or wrongly, seem to be saying a similar thing.

It's interesting that you quote the same link to Luminous Landscape to prove your point that I used in post #38 to prove mine. |=)|

The important thing is that, whatever method each photographer uses to obtain the results they're happy with, is the right one for them.

Click to expand...

This is also my belief and it makes sense to my way of thinking. If we ask how someone would map from 2^12 values to 2^8 values, and look at the top 16 values, between 4079 and 4095, it would make sense for the first 8 to map to 254, and the next 8 to map to 255. So, that means that 8 tones have been mapped to pure white. In other words, some highlight information has been lost, with some whites blowing out. In other words, gradations of tone are less subtle. But in practice I think it is more complex than that. The JPG exposure algorithm probably favours areas of most interest (mid tones) at the expense of highlights and shadow detail. So I would not be surprised if mid tones are expanded. Hence there is probably significant loss of highlight information.

I think where you see the biggest difference is if you get the exposure wrong, or there is high contrast.

Incidentally I think that some MF digital cameras work at 14 bits, giving 16,316 distinct brightness values.

Personally I use RAW as CF cards are not that expensive.