16 or 8 bit tiffs

[matt shepherd]

Ok so I am not all that experienced in post production so my question is after I edit my raws I save them as a 16 bit tiffs is this necessary or should I only save as an 8 bit?

Thanks Matt Shepherd

[Kym]

I keep my raw images in lightroom, plus PSD for those I edit in PS.
Keep your important images in 16bits - it gives you the best future edit options.

[Damo77]

Matt, it partially depends on your colour space. sRGB images are quite safe in 8-bit (assuming you've done your major tonal adjustments in raw, and are only likely to do tweaking in PS). ProPhoto RGB images must be 16-bit. Adobe RGB is in a kind of grey area.

[Damo77]

By the way, keep this (http://damiensymonds.blogspot.com/2010/02/16-bit-to-8-bit.html) in mind.

[ricktas]

I disagree with the above. It depends on what you are using the photos for, now and into the future.

An 8-bit RGB (red, green and blue) image uses numbers from 0 to 255 to represent each constituent colour, or "channel" in the image. Zero is the complete absence of that colour while 255 represents the maximum amount of that color. Thus, a value of (255,0,0) represents pure red, (0,255,0) would be pure green, (0,0,0) and (255,255,255) would mean pure black and pure white respectively, and so on. Zero through 255 gives 256 total distinct values that each of these three channels can have. If you multiple 256 times 256 times 256, you get 16.7 million different combinations. That's a lot of different colors, hues and shades.

By contrast, a 16-bit image provides us with 65,536 values for each channel instead of only 256. Multiplying this number by itself three times over gives us an astronomical 281 trillion total possible colours. The file will now take twice as much space of course, but that space clearly gives us a lot more information.

Now the interesting bit. All those extra values do not give us more colours, they give us more accuracy of colours within the defined colourspace.

In the end it is up to the individual, but remember as soon as you save that TIFF as a JPG for web display etc, it becomes 8-bit anyway as JPG is an 8-bit format. If you shoot in RAW and are editing for the web, 8-bit TIFF is fine, cause that's where you end up anyway. If you want more accuracy in your colours, use 16-bit. Personal choice ultimately. I always edit in 16 bit, cause in the future we will see better screens, better printers and the detail in those 16 bit files will be worth having. You can convert down, 16 to 8, but going the other way doesn't restore your original data, it just makes it up, to fill the 'gaps'.

Home printers are fairly much all 8-bit, but some pro labs can and will print from a 16 bit Tiff file. Something to consider if printing big and colour accuracy is paramount to the result.

Keep your original RAW files, or if you shoot JPG always keep the original file and work on a copy. That way you can always go back and start again in the different bit depth (if you shoot raw) if you want to sometime in future.

[matt shepherd]

thanks for all your help. looks like I will save the ones that may get printed in 16 bit.