Bit depths and how they affect the image

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Paramvir Singh
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Bit depths and how they affect the image

Post by Paramvir Singh »

Lots of mostly un-read/ill-informed people will always try and convince the Cinematographer to choose a low end 'digital format' because it 'looks good'.

In such a case remember what they probably mean is
'its cheap and will save me a lot of money, anyway what do you know, I can SEE that it looks good enough'.

one important criteria for an image is its pixel bit depth. the higher the bit depth, the higher the range of colours that it contains.

Mini DV is typically 8 bits. It means it has 2-to-the-power-8 shades of grey.
so it means Mini DV can record 512 shades of grey.

DigiBeta records 10 bits meaning : 1024 shades of grey.

Red One claims recording at 12 bits linear, meaning 4096 shades of grey.

Arri D21 records 12 bits log (wow), meaning 4096 shades of grey. but smoother since its log.

So how does that affect you? the more the shades that you record, the higher the scope you have for pulling clean mattes and better colour manipulation in post.

I tried created a gradient in Combustion in 8 bits and then in 16 bits.
Then I exported the two files to Photoshop for manipulation and applied the same Curve to each.
See how the 16 bit file holds up as against the 8 bit. Also note the banding which is more pronounced in the 8 bit image.

(note: the information here COULD be inaccurate and is only for illustration purposes. also, I had to convert the images to standard jpegs for internet viewing, which does affect image quality)
Attachments
8 Bit Untreated Image
8 Bit Untreated Image
8 Bit Treated Image
8 Bit Treated Image
Last edited by Paramvir Singh on Sat Nov 07, 2009 7:19 pm, edited 2 times in total.
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Paramvir Singh
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Re: Bit depths and how they affect the image

Post by Paramvir Singh »

I tried the same treatment curve on the 16 bit image.

NOTE: the untreated imges, both 8 bit and 16 bit, look similar. This is what many people will tell you "the image looks good enough", but pass it through some post and see how you will tear your hair. (if any of it is left AFTER shooting certain digital formats).
Attachments
sixteen0bit.jpg
16 Bit Untreated Image
16 Bit Untreated Image
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