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16-bit scanning (1 Viewer)

Andrew S

Kentish Mother
16-bit per channel scanning

I have a Minolta Dimage Scan Elite 5400, which seems to do a good job as far as I am concerned scanning negatives and slides.

However I am not convinced that I am using it to its full potential. It has the capability to scan at 16-bit colour depth per RGB channel, which I believe means that each colour channel has 65,536 possible values, rather than 256 with 8-bit. (Or to put it a different way, each value of an 8-bit per channel scan is subdivided into 256 different values.) 8-bit per channel is the same as 24-bit colour depth (ie 8 bits per channel x 3 channels).

The scanner comes bundled with Photoshop Elements 2, which irritatingly cannot cope with 16-bit per channel colour, so I have tended to scan at 8-bit (not a particularly conscious decision originally as 8-bit is the default). This generally results in fine results, particularly as I do nothing but look at the results on my monitor at the moment.

However, when trying to redeem some underexposed photo, or retrieve some skulker from the depths of the shadows of a photo, by adjusting the levels. It seems to me that in these cases it would be much better to scan at 16-bit, then adjust the levels, then save as 8-bit, if that is the desired result. This should result in much more colour detail in the finished result (subject to the limitations of the original film).

Is this the correct analysis?

I can use the scanner software to do level adjustments to the prescan, and then scan at 16-bit and reduce to 8-bit, which I think should get to the same result, although I am not entirely convinced. Also I like to scan in batches, which is not ideal for this sort of individual attention.

Alternatively I can use a different image processing program. I am not particularly keen on paying for the full Photoshop, but what about Paintshop Pro, which I have used before and liked - will this take 16-bit images? Or any other suggestions.

Also, once I get into printing my images, I assume there will be some benefit in having 16-bit images, is this right?

Thanks for staying to the end of this, and any comments gratefully received!

Andrew
 
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Hi Andrew,

I can confirm PSP does support 16-bit images, but I cant coment any further, as I'm only just starting playing with RAW images from my 300D

Paul
 
Thanks Paul. Enjoy the new camera - they do look tempting...

I have been looking at this a little further and have downloaded the PSP trial. Whilst it can indeed open the 16-bit files, I think this is actually a cheat, and what it is doing is converting them to 8 bits per channel without admitting it. If you open a 16-bit file and then save it without altering it, it suddenly halves in size. (I presume it will do the same to your RAW files, which I believe are 12-bit, although obviously it won't halve them if that is right.) At least Photoshop Elements warns you before degrading your pictures...

So I then downloaded the Photoshop CS 30 day trial, which identifies files as 16 or 8 bit, which confirmed this.

So the answer is to scan at 16-bit, and then either use Photoshop CS to adjust the levels, or use the scanner software to adust the levels as part of the scan process. I know a lot of people resist using the bundled scanner software in favour of Vuescan or similar, but I haven't got that far yet. However, the histogram looks a lot smoother the first way, although the second way easily beats doing at 8-bit for smoothness.

Having said all this, for monitor use there is not a particularly noticeable difference between the 8 and 16-bit approaches other than with rather extreme slides (with very dark areas).
 
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Hi Andrew,

I just tried that, and yup it does reduce it. As you say you cant really tell the difference on a monitor or A4 print, so for me it's not worth worring about. I'm saving for a EF17-40mm L W/A zoom at the moment so I've got a long wait before I go for PS CS.

Paul
 
We come from the land down under!!

A fascinating insight into your scanning sagas!!

Hi Andrew, this is Steve Knott here..an expat Brit missing blighty badly-- based in Perth, West Australia..
So how you going 3 months on re 16 or 8 bit best scanning work practise?

I am very intrigued because I am buying either the Minolta 5400 or Nikon LS5000ED
soon so that I can produce first class 50mb+ files. On this why did you choose the Minolta over the Nikon please?

I want the best scans possible, so if Paint Shop Pro or Photoshop Elements converts them to 8 bit that's a worry.. To retain the saved 16 bit scanned image do you have
Photoshop CS now?

To refresh you, this paragraph of your earlier posting's relevant..

So the answer is to scan at 16-bit, and then either use Photoshop CS to adjust the levels, or use the scanner software to adust the levels as part of the scan process. I know a lot of people resist using the bundled scanner software in favour of Vuescan or similar, but I haven't got that far yet. However, the histogram looks a lot smoother the first way, although the second way easily beats doing at 8-bit for smoothness.

Love to hear from you,

no worries mate!!

Steve
 
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