4-bit vs. 16-bit scanning


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aaron-xp

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I've done searching through the internet and the forums, but I can't get a definitive reply on the difference between 4-bit and 16-bit scanning for 120 films.

I come across terms like the depth of colours and stuff, but I would like to find out if the difference between 4-bit and 16-bit film has anything to do with the ability to have larger prints.

Thanks! :)
 

I'm not an expert and neither do I know the exact calculations, but 4-bit is really low but fastest. An 8-bit scan is good for very well exposed photos where minimal manipulation is required, and I suspect that anywhere more manipluation of files in post production is required, the extra data in 16 and higher bit depths helps preserve quality as you work the files. As mentioned earlier, I'm a newbie in this area, so more research and trials may be in order.
 

Not an expert either, but my understanding: bit depth is a measure of the amount of color shades/levels of variation that are captured for each color in a file. So, a 4 bit scan basically has 25% of the shade levels compared to a 16-bit file. That means that when printing, there won't be as subtle a change in the the image of, say, a green field -- instead of the file being able to use 200 shades of green in a 16 bit file, a 4-bit file might only have 50 shades (the numbers aren't accurate, I'm just using them to show the difference). So, if you have a photo with rich colors and a lot of different variations in color, etc. You are losing out if you go 4-bit. It's a similar decision to choose MF vs. 35 mm....

So, if you scan 16-bit JPEGs, you have more information to work with. When blowing up a file, more info is better (usually) -- more data to work with. If you were talking snapshots, I would think 4-bit would be fine. But if you're shooting MF, I assume you're doing so because you love the quality of the detail a big negative gives you, right? Scanning 4-bit to me is like driving a Ferrari but using the cheapest/lowest octane gas you can find -- it won't give you the experience you want - why buy the Ferrari if you're not going to use it to its fullest potential? (Again, this is only if you are into the MF experience and want to blow up your pics and maintain the quality of the image).


You have to make a similar decision in file type -- JPEG vs. TIF or RAW. RAW/TIF saves much more information; JPEG extrapolates information and saves what it thinks is important, thereby making a smaller file. When scanning, y ou can usuallly get either JPEG or TIF (in the shops). Again, if you scan a file as a JPEG, the computer decides what info is kept and what is thrown away. JPEG does a great job, but if you are someone who likes to manipulate your files afterwards, then you're working with less info. TIF files capture a lot more info (and of course are then a lot bigger) and are more expensive. But again, if you're using MF to get the rich big-file experience, you might want to think about doing TIFs. At least for your favorite images.

What I've beend doing lately is scanning 4-bit JPEGS of every roll of MF film and seeing which of the negatives have a lot of potential. Then I'll go back and scan those as 16-bit TIF files so i can play with them. That's the beauty of scans -- you can repeat. So you can do your first scans less expensive, and they work great for Flickr, etc. If there are a few you love and you want to print large prints, you can always go back and scan again selectively to save $$, and then use that file to get the size/quality you want.

Oh, and last (I'm sure you know this), you need to look at the DPI of the scan as well if you are just interested in blowing up a scanned JPEG file and printing large without manipulating. So it's 3 things to consider (Bit-depth, file type and DPI) when you're thinking about scanning. And the decisions depend on what exactly you want to do with the image (and of course how much you're willing to pay ;)

EFD
 

EFDixon, that sounds like an excellent explanation!

Clear, detailed and easy to understand! :thumbsup:
 

There is a imacon scanner (16 bit) available at Shriro for testing. try contacting them for a test. the scanner is available for rental.
 

I've done searching through the internet and the forums, but I can't get a definitive reply on the difference between 4-bit and 16-bit scanning for 120 films.

I come across terms like the depth of colours and stuff, but I would like to find out if the difference between 4-bit and 16-bit film has anything to do with the ability to have larger prints.

Thanks! :)

Are you sure it's 4-bit/16-bit, not 4-base/16-base?
Seems unlikely anyone would do 4-bit scanning - that's only 16 levels per channel :sweat: No it's not 25% of 16-bit, it's 0.024% of 16-bit. As for 4-bit JPEG - that's totally another matter - it means the lossy-compressed image uses 4 bits per pixel on average, after compression from some original source image.

http://en.wikipedia.org/wiki/Photo_CD
Base 512 × 768
4 Base 1024 × 1536
16 Base 2048 × 3072

Well, for 120 film, 16 base is still pretty small a scan. Any good flatbed scanner with film adapter could handle 16 base with no problem.
 

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I got a little confused between the 4-bit and 4-base thing.
Got it! Thanks! :)
 

Hi guys, 4-bit or 16-bit scanning refers to the number of steps of gradation from dark to brightness or the gradation of RGB colours. 10bits has 1024 steps of gradation.
12 bits has 4x 1024 steps of smooth shades of colour.
So, 16-bit has more shades of colour details, or refined.
 

So, if you scan 16-bit JPEGs, you have more information to work with. When blowing up a file, more info is better (usually) -- more data to work with. If you were talking snapshots, I would think 4-bit would be fine. [...]

JPG doesn't support 16bit. In the same way, 4bit is hardly usable for any image.
 

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