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Bit depth of RAW/DNG
How do I find out the bit depth of the raw (.raf) files taken with the Fuji E900? I can't find the info in lightroom...

Comments (12)

I think that almost all RAW files are 12 bits per pixel. The recently announced Nikon D3 and D300 produce 14 bits per pixel..

Note that this is the number of bits before the RAW data is processed and is luminence data only. Bayer interpolation produces output with 2 bytes, 16 bits, per colour (RG&B), 6 bytes or 48 bits per pixel, although most RAW processors will have an option to output at 24 bits per pixel.Chris R..

Comment #1

It also varies from scene to scene..

I recently analysed a few raw files from my 400D.Although all photos looked pretty good the raw data differed greatly,.

In one sunny outdoor scene 94% of the data stretched from ~200 to ~1800 resulting in actual usable raw data of 11 Bits..

There were some scenes which only had a range of 9-10 Bits, and I guess under ideal conditions I could create a picture, that would encompass 12 Bits of data..

However since pretty much all raw file formats use some kind of lossless compression, I wouldn't be surprissed if the data is actually stored as 16 Bit, since it is just a lot easier to handle and provides lots of room to grow..

If you use something like huffman compression using 16 Bits instead of 12 Bits would increase file size by a few kilobytes only..

Bye,Gaspode..

Comment #2

So the bit depth is not something you can just check like other Exif attributes?..

Comment #3

Furfoot wrote:.

How do I find out the bit depth of the raw (.raf) files taken withthe Fuji E900? I can't find the info in lightroom..

On the chip/sensor of any given camera the gathered light causes an Analogue voltage to be felt at the end of the "well" (pixel). This analogue voltage is enlarged by a conventional (analogue) amplifier. It is then passed to an Analogue to Digital Convertor (an ADC)..

It is at this stage that the bit depth of the RAW is decided. Most outputs from the ADC are 12bit but some (I beleive that the Minolta A1 was one of them) are 14bit..

From there, camera internal digital processing takes over and the final output depends on the setting one has chosen..

JPEG: has been designed to only handle 8bit images so an algorithm is used to compress the 12bit data to 8bits to comply with this standard ... and one is then stuck with all the compromises that this invloves..

The TIFF standard can be in either 8bit or 16bit format. Most manufactuers choose to place their 12bits of data within the 16bit "frame"..

RAW. The full 12 (or 14) bit data is placed in a 16bit frame and saved. It is meant to be unprocessed data (for later developement by your PC and software of choice) but some manufactuers do a little "pre-processing" even on this data before it is saved to the cameras card..

So, to finally answer your queston ! The true bit depth of your camera is not variable and you should be able to look it up in the cameras' specifications..

Hope that this helps..

Chas.Canada.==============Do Not Listen to What I Say ... Listen to What I Mean !...

Comment #4

Philip Peter wrote:.

It also varies from scene to scene..

I recently analysed a few raw files from my 400D.Although all photos looked pretty good the raw data differed greatly,in one sunny outdoor scene 94% of the data stretched from ~200 to~1800 resulting in actual usable raw data of 11 Bits.There were some scenes which only had a range of 9-10 Bits, and iguess under ideal conditions I could create a picture, that wouldencompass 12 Bits of data..

If AD converter is 12bit, then you always has 12bit data -doesn't matter what image may contain. As analogy: if you record sound on 16bit machine, recorded data will be 16bit -again, doesn't matter if you recorded complex orchestral sound or only pure 400Hz..

So, saying 12bit data image sometimes contain only "range" of 10bits, can't apply..

What we see (on histogram) isn't bit range, bot how's light intensity spread over that 12bit (or 14bit) data..

BogdanMy pictures are my memorieshttp://freeweb.siol.net/hrastni3/..

Comment #5

I'd like to answer your question with an other question. Why bother?.

Its either more than 8 or less than 16 bits pr channel..

If you save the pictures in jpg, it gets crunched into 8..

If you save in raw, it stays what ever it is until you open it with a raw converter. Then you have to chose between 8 or 16 to work with..

Then at the end of the day, I guess that 99% of photos end up in jpg which means that everything gets crunched into 8 bits pr channel. (Since you have 3 channels, thats were 24 bit color comes from.).

In theory, you should shoot raw, save as 16 bit pr channel, postprocess as 16 and when your finished - save as jpg..

But I'm a noob and my knowledge is purly theoretical and often wrong, which is why I hang out here and learn..

DNG is interesting. Its Adobe's atempt to create an open Raw format. like jpg is an open format. The various Raw covnersion algoritms are proprietary. I think it should be supported.

Tom..

Comment #6

Hbx2004 wrote:.

Philip Peter wrote:.

It also varies from scene to scene..

I recently analysed a few raw files from my 400D.Although all photos looked pretty good the raw data differed greatly,in one sunny outdoor scene 94% of the data stretched from ~200 to~1800 resulting in actual usable raw data of 11 Bits.There were some scenes which only had a range of 9-10 Bits, and iguess under ideal conditions I could create a picture, that wouldencompass 12 Bits of data..

If AD converter is 12bit, then you always has 12bit data -doesn'tmatter what image may contain. As analogy: if you record sound on16bit machine, recorded data will be 16bit -again, doesn't matter ifyou recorded complex orchestral sound or only pure 400Hz.So, saying 12bit data image sometimes contain only "range" of 10bits,can't apply.What we see (on histogram) isn't bit range, bot how's light intensityspread over that 12bit (or 14bit) data..

You are right, the bit depth is of course determined by the AD Converter and is a constant..

What I was going on about was the range of the usable information, which will tell you about the dynamic range of the scene and how much you can adjust a raw image, without getting visible degradation..

The data is of course in 12 Bit format, but the information contained in these 12 Bit could as well be saved in only 10 Bit, in other words i'm not using the full potential of the ADC and the raw format, since the 11th and 12th bit will always be zero..

Bye,Philip..

Comment #7

What did you use to analyse your raw file?.

Tom..

Comment #8

I made a small program using jrawio ( http://jrawio.tidalwave.it/ )..

This was part of a bigger effort to create a small raw processor..

If I were to make a program that just analyses raw files to determine the range of usefull information, I would probably use dcraw and create a small command line program for batch processing..

Bye,Philip..

Comment #9

Philip Peter wrote:.

Hbx2004 wrote:.

Philip Peter wrote:.

It also varies from scene to scene..

I recently analysed a few raw files from my 400D.Although all photos looked pretty good the raw data differed greatly,in one sunny outdoor scene 94% of the data stretched from ~200 to~1800 resulting in actual usable raw data of 11 Bits.There were some scenes which only had a range of 9-10 Bits, and iguess under ideal conditions I could create a picture, that wouldencompass 12 Bits of data..

If AD converter is 12bit, then you always has 12bit data -doesn'tmatter what image may contain. As analogy: if you record sound on16bit machine, recorded data will be 16bit -again, doesn't matter ifyou recorded complex orchestral sound or only pure 400Hz.So, saying 12bit data image sometimes contain only "range" of 10bits,can't apply.What we see (on histogram) isn't bit range, bot how's light intensityspread over that 12bit (or 14bit) data..

You are right, the bit depth is of course determined by the ADConverter and is a constant..

What I was going on about was the range of the usable information,which will tell you about the dynamic range of the scene and how muchyou can adjust a raw image, without getting visible degradation.The data is of course in 12 Bit format, but the information containedin these 12 Bit could as well be saved in only 10 Bit, in other wordsi'm not using the full potential of the ADC and the raw format, sincethe 11th and 12th bit will always be zero..

Bye,Philip.

Hi Philip,.

I see we understand each other  I just though, sometimes it is needed to be a bit more specific -otherwise there can be a lot of confusion (happens anyway)..

Q.: So, it does happen last two bits are zero for whole image (=for all sensor sites)? I wonder how come that happens... I mean: why isn't full AD conversion potential used all the time (in all cases)? Or am I misssing something?.

Greetings,BogdanMy pictures are my memorieshttp://freeweb.siol.net/hrastni3/..

Comment #10

Thanks Philip..

Even if I grew up with command line, that was yesteryear. I looked at dcraw, but bibble and ACR suits old farts like me better..

Java, thats something I drink.Tom..

Comment #11

Hbx2004 wrote:.

I see we understand each other  I just though, sometimes it isneeded to be a bit more specific -otherwise there can be a lot ofconfusion (happens anyway)..

Q.: So, it does happen last two bits are zero for whole image (=forall sensor sites)? I wonder how come that happens... I mean: whyisn't full AD conversion potential used all the time (in all cases)?Or am I misssing something?.

It's not that clean cut, there is some information, I just did some more comprehensive testing and found that pretty much all values occour, however for values below ~250 there are usually only one or two pixels that have the given value. There are some odd jumps up to 14 pixels every ~10 increments, but I haven't figured out why yet.However these low values can easily be due to noise in the absolut black values..

Above the 1% clipping values the distribution is a bit different, in one very high dynamic range photo I have, the data goes continously up till 4056, however there are never more than 65 pixels that take any single value..

However there are 62 470 pixels that have a value of 4056, I supect this is due to some characteristic of the photosites..

In a different photo with less dynamic range, there only very few pixels that have a value higher than 2400..

Of course these are just some random findings, I haven't looked at different isos and lighting conditions. I also have only looked at very few samples..

One could argue that a perfect exposed photo should have a distribution ranging from 0 to 4095. The sensors and ADC seems to allow it..

But as probably everyone has experienced a technically correct photo doesn't necessarily make a good photo, therefore I assume that there are only verry few photos that have an actual usable range from 0 to maximum..

Bye,Philip..

Comment #12

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