Consensus needed on benefit of 16-bit editing

Started Sep 16, 2005 | Discussions thread
Henry Domke
Forum MemberPosts: 58
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Tim Grey offers opinion on the benefit of 16-bit editing
In reply to Henry Domke, Sep 26, 2005

Tim Grey responded to my question today so I thought I would add it to the mix. Interestingly he says "yes and no" to high bit editing. Tim puplishes the DDQ Newsletter http://www.timgrey.com/ddq/index.htm

Here are his exact words:

There are two key points I'd like to make here. The first is to agree with Dan that the 16-bit advantage is indeed a benefit in theory for color photographs, and with today's technology there is no visible benefit in the final results. Having said that, I still prefer to optimize images in 16-bit. This is simply because I prefer to maintain as much information in the image as possible, even if that additional information doesn't provide a benefit today. Part of this is philosophical (meaning you could very easily discard the notion), but part of it is practical. The practical side of it is the assumption that at some point in the future, we'll have displays and printers that are actually able to take advantage of high-bit data to produce a difference that improves upon what we see with 8-bit data. For example, I expect that at some point there will be printers available that produce a visually better result from 16-bit data than they do with 8-bit data, and at that point you'll wish that all your images had been optimized and saved in 16-bit. Of course, I could be totally wrong on this assumption about future output capabilities.

So, you're looking for a definitive answer. That answer is that, today, there is no real benefit to saving your color photographic images in 16-bit per channel mode. The only benefit would occur with images that require very significant adjustment, but those images would be the exception, as the adjustments really need to be quite significant for there to be any advantage to 16-bit. I'd still prefer to keep those files in 16-bit mode with all layers intact, especially considering how cheap storage is these days.

Keep in mind that for grayscale images, as discussed in the prior question, there is indeed a benefit to 16-bit. So, while you can get excellent results with most color photographs in 8-bit, for grayscale images it really is important to work in 16-bit if that data is available in the original.

The second point I want to make will actually further erode the notion that you need to work in 16-bit, but I'll mention it anyway. That is, even if you strip out a significant amount of information in an 8-bit image by the adjustments you make, resulting in gaps in the histogram, you may not produce any posterization that is visible in the monitor display or final print. I sometimes do a demonstration with an 8-bit color photograph in some of my workshops, creating a Posterize adjustment layer to demonstrate the results of extreme posterization. I start with the value very high (the maximum is 255) and then gradually work it down, asking the students to tell me when they see evidence of posterization in the projected image. I generally get down to somewhere around 40 or 50 before the first student is able to see any signs at all of posterization, and even then it is only minor. The histogram at that point looks quite ridiculous, but the image still looks like a photo. This demonstrates that you can indeed push an image very far before any image quality problems become evident.

So, it is probably quite clear at this point that for color photographs there's not a strong argument in favor of working in 16-bit mode. I still prefer it, and still recommend it, but this is largely for two reasons. One, it virtually guarantees you can't strip out enough detail to cause posterization problems in the final output, even with significant adjustments, and two, it ensures you are retaining the maximum amount of information in your images that you will hopefully be able to take full advantage of in the future as display and output devices advance. I for one find it hard to believe, especially considering how far we've come over the last five years, that we won't have printers in the future that can achieve a benefit from 16-bit data.
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Henry Domke

http://www.henrydomke.com/

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